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0. Who this is for

These guidelines are for users of the AppSDK App SDK who want to use it to create a scene for rendering with V-Ray from the data in their host application scene. We will not discuss details on how to write code with the AppSDK App SDK here - there are separate docs and examples for this included in the SDK package. Rather we will cover what V-Ray plugins to add to the scene, how to link them and what parameters to set.
Note: This document will be updated and extended over time.

1. Introduction

1.1. A note on terminology

• plugin: We use the term plugin a lot. Technically it could mean a plugin DLL for V-Ray (even V-Ray itself is a kind of plugin) or the type defined in it, which is for example a class in the programming sense, or finally an instance of this class which resides in memory and can be saved to a scene file. We will be using the term plugin to refer to plugin instances.
• exporter/translator: We call the piece of software that translates some native scene format to the V-Ray scene format an exporter or a translator, interchangeably. Basically what it does is creating a bunch of V-Ray plugins and setting their parameters. Note that we also use the verb "to export" sometimes in reference to the act of saving out the scene (which was already translated) to a *.vrscene file.

1.2. V-Ray scene contents

We could informally define three kinds of plugins that build up a V-Ray scene.
One would be the so called "top-level" plugins, which can exist on their own, without being part of some plugin tree. Lights are top-level plugins for example. They can also receive input from other plugins of course, but they do not output values to other plugins.
The plugins which are not top-level serve as input for parameter slots which require a plugin of certain type. For example a material plugin may require an optional texture input and you'd reference a texture plugin there. The texture plugin may receive input from a UVW generator and so on.
The third kind would be a special type of top-level plugins which only have one instance. These are basically settings plugins. Most of them have "Settings" in their name, but a few don't. The V-Ray camera is also defined by such a singleton settings plugin.

There is an example tiny scene in section 7. Its contents should become understandable by reading the following sections.

1.3. Parameter types

The following are the types recognized in a V-Ray scene (think .vrscene file). They have corresponding types in the different AppSDK App SDK language bindings. The SDK uses the respective basic language types wherever possible and defines custom type classes for the rest.

• Basic types: int, bool, float, Color (3 float RGB), AColor (4 float ARGB), Vector (3 float), string (UTF-8), Matrix (3 Vectors), Transform (a Matrix and a Vector for translation).
• Objects: references to other plugin instances.
• Typed lists: The typed lists in AppSDK App SDK are IntList, FloatList, ColorList, VectorList, TransformList and VectorList PluginList.
• Generic heterogenous heterogeneous lists: The AppSDK In C++, the App SDK uses a generic type class called Value for items in a generic list. In C#, Python and Node.js, native language types are used (lists or arrays). Note that generic lists can be nested.
• Output parameters
  : These are additional values generated by a given plugin which may be used as input by others. For example the TexAColorOp plugin  plugin (described in section 5.2) can be referenced directly as a texture, resulting in its default color texture output, but you can also refer to any of its other outputs, like sum, difference, maximum etc. for different results (Note: in some cases connecting an output parameter to an input parameter may not work directly, so you'd have to make the connection through a wrapper plugin like TexAColor or TexFloat).
  In App SDK output parameters are represented by the PluginRef type which combines a plugin reference and an output name.

Parameter polymorphism is an important feature of V-Ray. Texture parameters accept simple (basic) values, so instead of creating an additional texture plugin which generates a single color you just set a Color value to the texture slot. Same goes for float textures and single float values etc. You can also set the value of a texture parameter to an output parameter as described above.

1.4. V-Ray scene file format

V-Ray uses a text based scene file format (.vrscene). It is quite simple which makes it convenient to debug and modify by hand. The format is case-sensitive and a little similar to JSON. Large data values, such as geometry definitions can be compressed (and text encoded). The file contains consecutive plugin instance definitions: type, instance name, parameter list. Nesting is not supported.
The main rules are:

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It is important to note that the order of definition of plugin instances generally does not matter. This also applies to a scene created in memory, even when you don't export it to a file. There are a few exceptions such as camera related settings plugins, which may not work correctly if V-Ray doesn't process them in a particular order.

1.5. Default values

Every parameter has a default value, so even after you create an "empty" plugin instance it is actually fully functional. Of course it might need data, as for example with geometry plugins, but a light will work right away (placed at 0 coordinates). That being said, some plugins have inconvenient default values, which almost always need to be changed (for example some settings plugins, such as the image sampler settings or some shadow parameters). We usually can't fix the defaults, because it would break existing user scenes. Nevertheless, unless you know what you're doing, it is recommended to stick to the default values. You are free to experiment, of course, but don't use values which you don't understand as they may have performance implications or quality implications or they may even break physical plausibility.
Note that when you export (save) a vrscene file it will always contain a bunch of settings plugins, even if you didn't create them. They will have default parameter values. This is how V-Ray always saves files.

1.6. Debugging and help

Apart from documentation included with the AppSDK App SDK and this guide, the help pages for 3dsMax and Maya on docs.chaosgroupchaos.com are a good source of parameter information and examples, although they use the user-friendly UI names for things and not the actual scene parameter names.
A very useful tool for basic parameter information is plgparams.exe included in the binary folder of the SDK. It lists all parameters for the specified plugin (or all plugins with -list) and their types, default values and text comments. Similar information can be obtained using the ListAllPluginsAndProperties example in the C++ folder (or equivalent code for another language).
It is often useful to save out your scene to a file to inspect if you did everything properly. For example you may have failed to set some parameter properly and you will see this in the file as a missing or incorrect value, although you can also check the result of the set operation in your code. You can try to pinpoint problems by deleting parts of the scene (parameters or whole plugins) and re-rendering.
It can be very helpful if you have a V-Ray for 3dsMax or Maya and use it to export vrscene files to see what plugins and parameters are written out. The exporters for 3dsMax and Maya can be considered "ground truth" (even though they may have an occasional bug or missing feature).
If you're getting a black render make sure your camera is positioned and oriented properly and not inside an object. Keep in mind the default up-axis is Z, but it can be set to something else, usually Y. You might also get invisible or black objects if something is wrong with the attached material. In this case you can still the object in the alpha channel, especially if there is nothing behind it.
Another thing to watch out for is V-Ray's errors and warnings, so always implement the DumpMessage callback.

1.7. "subdivs" parameters

1.7. "subdivs" parameters

You will see subdivs (subdivisions) parameters on many light and BRDF pluginsYou will see subdivs (subdivisions) parameters on many light and BRDF plugins. They control the number of new rays spawned for calculating glossy and diffuse effects on materials or the number of light and shadow evaluations and so on. The number of actual rays is proportional to the square of the parameter value. These can be used to increase or decrease sampling for the respective light or material, but we highly recommend leaving these at default values. We also recommend disabling local subdivs values altogether - see the DMC sampler section for details. Some of the settings plugins also have subdivs parameters which are ok to change, like the Irradiance Map and Light Cache for example.

Note: The reason the renderer uses the square of the parameter value is the property of the Monte Carlo integration method that to reduce noise (variance) by half (1/2 noise), you need four times as many samples (4x), to get 1/10 the variance you need 100x more samples... This way we get linear results from linear increases in the subdivs parameters.

2. Defining camera position

One of the first things you'd want to do is control your camera. This is done through the RenderView plugin. You will always want to create and setup this plugin, exactly one, in your scenes. (The exception is when you are baking textures - then you'd use BakeView.)

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• fov - The horizontal field of view in radians.
• orthographic - Enable to have orthographic projection instead of perspective .(RenderView::fov doesn’t matter in this case, in favor of RenderView::orthographicWidth).
• transform - A transformation (rotation transform - A transformation (rotation + translation) which defines where the camera is and how it is rotated. The matrix is in column-major format and you will need to calculate it yourself. You can't set rotation angles as in most 3D software. The default camera orientation with identity matrix is so that +ZY is pointing up and +Y -Z is the view direction. If your scene uses +Y for up-axis, you will need to set V-Ray's scene up-axis accordingly - see the Units subsection in the settings section below.

For advanced camera effects, such as DoF, exposure, distortion, vignetting, etc. you will need to enable the physical camera in addition to RenderView. See the Physical camera subsection in the settings section below for details. You can also use SettingsCameraDof instead, if you only need depth of field (see 6.11. Miscellaneous).

3. Creating lights

Good lighting is the most important thing for getting good photorealistic renders. It also affects image noise and performance. Some lights (generally the simpler ones, especially the first four in the list) render faster and with less noise than others. Things that may affect noise and performance of lights are: having a texture instead of flat color; having a complex mesh; being an area light with small relative size.

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The rectangle, mesh and dome lights can be textured. Keep in mind that the texture files are re-sampled at a resolution controlled by a tex_resolution parameter which has a default value of 512 for dome and rectangle and 256 for mesh lights. So if the light texture looks too pixelated, especially on the dome environment, try increasing this resolution. This will of course increase memory usage and render time slightly.

4. Creating geometry

4.1. The Node plugin

Before we get to defining your actual geometry data, there is a top-level plugin for non-light-emitting objects called Node. It links the geometry data (geometry parameter) with a material plugin (material parameter) and positions it in the world (transform parameter). You could reference the same geometry in different nodes with different positions.

4.2. Geometry sources

Lets look at the main geometry source plugins (we will ignore some others):

• GeomStaticMesh - The basic fixed geometry descriptor that you will use in most cases. Requires vertex and normal data plus optional UVW texture mapping coordinates.
  V-Ray static meshes work with triangular geometry only, so if you have larger polygons, you will have to triangulate them. The simplest way would be the ear clipping method for convex polygons. The triangle vertex indices are specified in counter-clockwise order in the geometry arrays for V-Ray if you're looking at the front face of the triangle.
• GeomStaticNURBS - Defines a smooth NURBS surface using control vertices and weights.
• GeomStaticSmoothedMesh - References another mesh plugin (usually GeomStaticMesh) and generates a smooth, subdivided version.
• GeomDisplacedMesh - References another mesh plugin (usually GeomStaticMesh) and generates a displaced version using a texture map.
• GeomHair - References another mesh plugin (usually GeomStaticMesh) and generates hair (can be tweaked for fur, grass, shaggy rug etc.) on it. Has many parameters for the size, shape and distribution of strands. This corresponds to VRayFur in 3dsMax and Maya.
• GeomMeshFile - Loads geometry from a file, a so-called geometry Proxy. The geometry is only loaded on-demand as a ray hits it, so in some cases such as distributed bucket rendering it may prevent unnecessary calculations and memory usage. The currently supported formats are V-Ray's .vrmesh and Alembic .abc. If you have a file in another format, i.e. .obj, you need to convert it with the ply2vrmesh tool.
• GeomParticleSystem - Generates many (usually small) particles.

4.3. Instancing

TODO: Instancer, Instancer2

5. Creating materials

Exporting materials is probably the most complicated part, because it may involve complex shader networks, especially in apps with high artistic control, such as the popular DCC tools from Autodesk. Nevertheless, you can get good results even by using only a few plugins.

and Instancer2 plugins can be used to efficiently instantiate a high number of objects in the scene from other geom source plugins. Often used for particles and vegetation.

• Instancer => N * Node (invisible) => GeomSomething

Instncer2 is also a geometry source and can be connected to a Node plugin:

• Node => Instancer2 => N * Node (invisible) -> GeomSomething
  
  and even
  
  
• Node => Instancer2 => Nodes => Instancer2 => etc.

5. Creating materials

Exporting materials is probably the most complicated part, because it may involve complex shader networks, especially in apps with high artistic control, such as the popular DCC tools from Autodesk. Nevertheless, you can get good results even by using only a few plugins.

There are two types of plugins There are two types of plugins involved - material (names start with "Mtl") and BRDF (names start with "BRDF") plugins. BRDFs describe what happens with light when it interacts with the surface, like refraction, diffuse scattering, etc. BRDFs get plugged into material plugins, which may extend their behavior or combine them. Finally the material plugin gets plugged into a Node that links it to a geometric object in the scene.

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Note: There are some material and BRDF plugins that still exist for compatibility reasons, but we don't recommend you use them. For example instead of connecting MtlDiffuse to a Node, you should create BRDFDiffuse -> MtlSingleBRDF::brdf -> Node::material. Plugins with names ending with "_ASGVIS" can also be ignored. We don't have an exhaustive list of deprecated plugins at the moment.

5.1. Material and BRDF plugins

• MtlSingleBRDF - The main material type that needs to be connected to Node::material.
• Mtl2Sided - Defines a (possibly different) material for the back side of triangles, as well as the front sides.
• MtlMulti - Use this together with GeomStaticMesh::face_mtlIDs to set different materials for subsets of triangles on one geometric object.
• MtlVRmat - Load a V-Ray shader from a .vrmat (formerly .vismat) file. Also supports loading MtlSingleBRDF materials from vrscene files. This is used for transferring materials between different host applications.
• MtlGLSL - Loads a GLSL shader from file and provides some parameters for it.
• MtlOSL - Loads an OSL shader from file and provides some parameters for it.
• MtlRoundEdges - Smooths sharp edges within a given radius by modifying normals.

Some advanced materials:

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• BRDFVRayMtl - The one BRDF plugin to rule them all. Combines all of the following except Cook-Torrance (not all at the same time - you choose a type). This is the preferred choice for most cases.

  Info
  See VRayMtl page for info on the different BRDF types.

• BRDFBlinn - The Blinn BRDF model for glossy highlights. See See Wikipedia article.
• BRDFCookTorrance - The Cook-Torrance BRDF model for glossy highlights. See Wikipedia.
• BRDFGGX - The new GGX (microfacet GTR) BRDF model for glossy highlights.
• BRDFPhong - The Phong BRDF model for glossy highlights. See Wikipedia article.
• BRDFWard - The Ward BRDF model for glossy highlights. See Wikipedia.
• BRDFDiffuse - A basic diffuse BRDF.
• BRDFGlass - A basic refractive BRDF.
• BRDFGlassGlossy - An extension of BRDFGlass that enables glossy refraction, meaning that rays with equal incoming angle refract at slightly different angles.
• BRDFLight - Self-illumination BRDF. Consider using LightMesh instead.
• BRDFMirror - A basic specular reflection BRDF.
  
  
• BRDFLayered - A weighted combination of any number of BRDF plugins. (This is also known as Blend material in the UI of V-Ray for 3dsMax and Maya.)

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• BRDFBump - Applies a bump map to some base BRDF.
• BRDFMultiBump - Combines up to 4 bump maps.

5.2. Textures and UVW generators

The BRDFs (and some lights) have many Color, AColor and Float parameter slots that can be textured. You will usually just load texture files, but V-Ray also offers many procedural textures, as well as texture plugins that serve as modifiers (i.e. apply some simple function, combine textures, extract data from one of the channels etc.). There are over 200 texture plugins, so we will only look at the most important ones. Many of the plugins are made for specific host applications. Apart from the texture data itself, V-Ray uses UVW generator plugins to generate UVW mapping coordinates or modify the original data from the geometry source. Using a UVWGen plugin is not obligatory.

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• UVWGenChannel - Modifier for UVW data coming from the geometry source. The main parameter is uvw_channel - the index of the mapping channel data to use (i.e. GeomStaticMesh::map_channels). The default is 1 as in 3dsMax where indexing starts from 1, but in your application this may be 0 or something else. If you set an index of -1 V-Ray will take the first available channel. This plugin also has transform, wrap and crop parameters as well as the option to get UVW data from another UVWGen plugin.
• UVWGenEnvironment - Used to map spherical, cube, etc. textures on the environment color slot or on dome lights.
• UVWGenExplicit - Define explicit UVW data from a texture.
• UVWGenMayaPlace2dTexture - Similar to UVWGenChannel, but with more options.
• UVWGenObject -
• UVWGenPlanarWorld -

6. Scene and render settings

A general note on settings plugins: when you create a new Renderer object there are no instances of them, so you will need to create them before changing parameters. If you start rendering the AppSDK App SDK will create a SettingsOutput and if the render mode is RT it will create SettingsRTEngine. On the other hand, if you're loading a scene from file, it will have instances of most (but not all) settings plugins and you need to use them. This is because every time V-Ray exports a vrscene file it automatically writes out the settings even if they are at default values.

6.1. Image and region size

These are controlled from the SettingsOutput plugin, but it is one of the few exceptions where you should not touch the plugin directly. The AppSDK has APIs for setting image and region size (i.e. renderer.setRenderRegion, depends on language).

6.2. Image sampling and filtering

V-Ray has several types of image samplers. These are algorithms that determine how many samples to take for each pixel. This is combined with an image filter, which can soften or sharpen the final image.

The image sampler is controlled from SettingsImageSampler. These are the four types for its type parameter:

6.1. Image and region size

These are controlled from the SettingsOutput plugin, but it is one of the few exceptions where you should not touch the plugin directly. The App SDK has APIs for setting image and region size (i.e. renderer.setRenderRegion, depends on language).

6.2. Image sampling and filtering

V-Ray has several types of image samplers. These are algorithms that determine how many samples to take for each pixel. This is combined with an image filter, which can soften or sharpen the final image.

The image sampler is controlled from SettingsImageSampler. These are the four types for its type parameter:

• type=0, Fixed sampler - It simply uses a fixed number of samples for each pixel. This is controlled by the fixedtype=0, Fixed sampler - It simply uses a fixed number of samples for each pixel. This is controlled by the fixed_subdivs parameter. This sampler type is not recommended.
• type=1, Adaptive sampler
• type=2, Adaptive subdivision sampler. This sampler type is deprecated.
• type=3, Progressive sampler

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• FilterBox - All samples within a box with sides 2*size are taken with equal weight.
• FilterArea - All samples within a circle with radius size are taken with equal weight.
• FilterTriangle - Sample weight falls off as a triangular function of off-center distance.
• FilterGaussian - The classical blur filter.
• FilterSinc - Less blurry low-pass filter. See Wikipedia.
• FilterLanczos (currently default in V-Ray for 3dsMax and Maya) - See Wikipedia.
• FilterCatmullRom - A cubic edge-enhancing filter.
• FilterCookVariable
• FilterMitNet - Mitchell-Netravali cubic filter with subjectively optimized compromise of blurring and detail in the additional blur and ringing parameters which correspond to B and C from the original paper.

To apply a filter, just create an instance of one of those plugins. You can use only one at a time.

Note: Do not create a SettingsImageFilter. It is deprecated. Use the plugins described above.

6.3. DMC sampler

We recommend leaving the parameters of SettingsDMCSampler at their default values, with the exception of use_local_subdivs. Set this to 0, so that only the global subdivs settings are used.

6.4. Global illumination

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The choice of GI engines and their parameters is paramount, especially for interiors where most of the illumination is indirect. Bad choices can lead to too much noise or artifacts and/or disproportionate render time for certain image quality. The common setup for interiors is Irradiance Map with Light Cache secondary and for exterior scenes it is often Brute Force primary with BF or LC secondary.

6.4.1. Brute force

The settings for Brute force are in SettingsDMCGI. There are only two parameters:

• subdivs - Controls the number of new rays spawned at each intersection point. We recommend using the default value.
• depth - The number of secondary bounces to trace before stopping. Larger values may increase the brightness of indirect illumination at the cost of render time. The default is 3.

6.4.2. Irradiance map

The Irradiance map is configured through SettingsIrradianceMap.

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• subdivs - The default is 50. Higher values can fix spot-like artifacts and lower values should improve render times.
• interp_samples - The default is 20. Setting a lower value may help if surfaces seem too blurry.

6.4.3. Light cache

The Light cache is configured through SettingsLightCache.

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• subdivs - The default is 1000. Higher values can fix spot-like artifacts and lower values should improve render times.

6.5. Environment

You can define environment background, lighting (GI), reflection, refraction colors or textures through the SettingsEnvironment plugin. Usually all slots have the same value. Environment textures use UVWGenEnvironment for spherical, cube etc. mapping.

You can also add scene-wide volumetric effects through the environment_volume list.

A special case is the Sun-Sky system. V-Ray has a special procedural texture, TexSky, for these environment slots that is coupled with SunLight. The color of the environment depends on the position of the Sun.

TexSky takes its parameters from SunLight if TexSky::sun is set. You can also use a TexSky without a Sun. For parameter details see the reference section at the bottom.

6.6. Units (scale)

Some calculations in V-Ray based on physics require accurate scaling of scene units to real world units like meters, Watts, seconds, etc. This is controlled through the SettingsUnitsInfo plugin with the properties listed below. This affects the physical camera, IES lights, volumetric effects, etc.

• meters_scale - Multiplying scene sizes by this value should yield object sizes in meters.
• photometric_scale - Scale for photometric lights.
• seconds_scale - When doing animation, this is the reciprocal of the framerate
• scene_upDir - This needs to be set if the scene has an up-axis different from the default, which is +Z. This parameter is meaningful only for some plugins, if the client wants to implement rotation, for example.
• rgb_color_space - Affects Sun/Sky color, color temperatures and dispersion in refractive materials.

6.7. Physical camera

Although the name doesn't hint at it, the CameraPhysical plugin is a settings plugin (singleton). It modifies the way camera rays are shot for effects like DoF (depth of field) and distortion and how they are integrated into the image - exposure. The position and orientation of the camera is still defined by RenderView. Many of the parameters are exactly the same as on a real world DSLR or video/movie camera.

• type - 0=still camera, 1=movie camera, 2=video camera   camera   Some parameters only apply for one of these types, because of the different types of shutter mechanism.
• fov - To use the value set here, also set specify_fov=1. Otherwise the fov from SettingsCamera and RenderView is used.
• vignetting - Note that the default value is 1.0. You may want to set to 0.0 to have a uniformly exposed frame.
• white_balance - This color tint may be counter-intuitive. If you set it to blue, you'll get a warm image and so on.
• blades_enable - Set to true to enable bokeh effects.
• bmpaperture_enable - Set to 1 to use the bmpaperture_tex texture.
• use_dof - Disabled by default. Set to 1 for ray-traced DoF. Note that just like in DSLRs the depth of the in-focus field depends on aperture and focus distance.
• use_moblur - Disabled by default. Set to 1 to enable camera motion blur.
• distortion_type - 0=quadratic, 1=cubic, 2=lens file from lens_file parameter; 3=texture from distortion_tex parameter

6.8. Color mapping

This is controlled by SettingsColorMapping.

The default values when you create a SettingsColorMapping plugin are different from the recommended values in 3dsMax and Maya for legacy reasons. These are the values you should use for new scenes:

• type=6     // 6=Reinhard mapping (plugin default is 0=linear)
• dark_mult=1   // don't change dark colors additionally
• bright_mult=1   // don't change bright colors additionally
• gamma=2.2   // close to sRGB (plugin default is 1.0)
• subpixel_mapping=0
• clamp_output=0
• clamp_level=1
• adaptation_only=2   // 2=only apply color mapping (plugin default is 0=apply both color mapping and gamma)
• linearWorkflow=0   // this is important - this option exists only for legacy scenes

There is one more place to control color mapping - BitmapBuffer for texture assets. It has two parameters for converting the image file colors - gamma and color_space.

<TODO> clarify gamma stuff

6.8.1. Linear workflow

In order for V-Ray to perform mathematically correct calculations, input and output color data should be linear. The results should only be converted to a non-linear color space (such as sRGB) for display. This is called linear workflow. 

For proper linear workflow, you need to set the SettingsColorMapping parameters gamma, adaptation_only and linearWorkflow to the values listed above. The parameter linearWorkflow is intended only for compatiblity with old vrscene files and should not be set to 1, despite its misleading name.

By Note that by default the VFB (V-Ray Frame Buffer) has its sRGB option enabled, so you will see the original linear image with sRGB applied as a post-process. The actual files you save will be linear as the actual data, but it depends on the file format (i.efrom the VFB or with VRayRenderer::saveImage() will be linear like the actual data if saved in a floating point format like EXR or VRIMG. On the other hand, most 8/16-bit integer formats implicitly save their data gamma-encoded (e.g. JPEG applies ~2.2 gamma for dynamic range compression because it stores 8 bits).

6.9. Stereo and panorama rendering

For spherical panorama rendering you need to:

• Change the type parameter of SettingsCamera to 9. (Note that type=1 is spherical, but not for panoramas.)
• Set the field of view to 360 degrees or rather 2*pi, because the fov parameter is in radians. You need to do this with the RenderView plugin and with SettingsCamera - both have an fov parameter. Also if you're using PhysicalCamera with specify_fov=1, set fov there too.
• Set the vertical field of view to 180 degrees. This may be a bit confusing: it is set through the height parameter of SettingsCamera. Also the value is not in radians, but in degrees.

. Applications that read JPEG handle that and display the data in the required color space, gamma-encoded or linear). Saving to such integer file formats with saveImage() or from the VFB button also bakes any color corrections done in the VFB, including the sRGB conversion. So these files will look exactly like you see them in the VFB. This does not apply to EXR and VRIMG.

6.8.2. Bitmaps

There is one more place to control color mapping - BitmapBuffer - for texture file assets. It has two parameters for converting the image file colors - gamma and color_space. The gamma parameter is considered only when color_space=1 and makes texture reads apply inverse gamma to decode gamma-compressed values to linear. Most integer formats will require setting color_space=1 and gamma=0.454545. When color_space=2, sRGB decoding is performed (similar, but not identical to color_space=1 & gamma=0.4545).

6.9. Stereo and panorama rendering

For spherical For cubic (6x1) panorama rendering you need to:

• Change the type parameter of SettingsCamera to 10.
• Set a resolution with aspect ratio 6:1 (or 12:1 if you are doing stereo). So for a stereo cubic panorama with 1000x1000 pixel cube sides you will render at 12000x1000.

For stereo rendering:

• 9. (Note that type=1 is spherical, but not for panoramas.)
• Set the field of view to 360 degrees or rather 2*pi, because the fov parameter is in radians. You need to do this with the RenderView plugin and with SettingsCamera - both have an fov parameter. Also if you're using CameraPhysical with specify_fov=1, set fov there too.
• Set the vertical field of view to 180 degrees. This may be a bit confusing: it is set through the height parameter of SettingsCamera. Also the value is not in radians, but in degrees.

For cubic (6x1) panorama rendering you need to:

• Change the type parameter of SettingsCamera to 10.
• Set a resolution with aspect ratio 6:1 (or 12:1 if you are doing stereo). So for a stereo cubic panorama with 1000x1000 pixel cube sides you will render at 12000x1000.

For stereo rendering:

• For CPU (Production or RT) rendering you need to create a VRayStereoscopicSettings plugin. It has to be created after SettingsCamera and SettingsOutput or it won't work! It's recommended to change the VRayStereoscopicSettings::focus_method parameter to 1 for panorama or 2 for normal camera.
• For GPU rendering you need to set RenderView::stereo_on to 1.  You might also want to set RenderView::
• For CPU (Production or RT) rendering you need to create a VRayStereoscopicSettings plugin. It has to be created after SettingsCamera and SettingsOutput or it won't work! It's recommended to change the VRayStereoscopicSettings::focus_method parameter to 1 for panorama or 2 for normal camera.
• For GPU rendering you need to set RenderView::stereo_on to 1.  You might also want to set RenderView::stereo_eye_distance to something like 6.5 (average human), instead of the default 1.0. It's recommended to change the RenderView::stereo_focus_method parameter to 1 for panorama or 2 for normal camera.

Also remember to set a double horizontal resolution for stereo. So if your normal render resolution is 640x480, make that 1280x480. The left half of the image will be the left eye view and the right half is the right eye.

6.10. RT Engine

If your renderer object was created with RT CPU or RT GPU mode parameter, you can control RT-specific parameters with SettingsRTEngine. Note that GI is always enabled when rendering on the GPU and cannot be disabled.

• trace_depth - The maximum depth for tracing reflection and refraction rays. Defaults to 5.
• gi_depth - The maximum depth for tracing diffuse GI rays. Defaults to 3. Lower if you need faster rendering and the scene is exterior. For interiors you may need to increase to get enough lighting, otherwise the scene may remain too dark.
• coherent_tracing - Experimental grouping of rays for coherency (disabled by default). This can improve performance on GPUs because they handle non-divergent code better. The first few sampling passes will have lots of artifacts, because entire groups of rays move together. Over time this should disappear and the final result should converge to the same image as when this is turned off. This option is only useful for interiors with lots of GI on GPU.
• cpu_bundle_size - A performance-related parameter. This is the number of rays that get processed together. The default value of 64 for CPU is good.
• cpu_samples_per_pixel - Number of samples to take for each pixel at one sampling pass. If you set lower, you will get images more often, which is good for interactivity. If you set it higher, you may reach final quality a tiny bit faster, because of the fewer back-and-forth sampling passes, but you will have to wait more between images and it may feel unresponsive when trying to change something in the scene.
• gpu_bundle_size - Analogous to cpu_bundle_size, but for GPU mode. The default is 256 and changing it may improve performance. The optimal value depends on GPU architecture and model, so you need to experiment. It may be below or above 256, but the default shouldn't be too far from the optimal performance.
• gpu_samples_per_pixel - Analogous to cpu_samples_per_pixel, but values can be set higher, because GPUs have better performance. You can still set it to 1 for maximum interactivity.
• progressive_samples_per_pixel - If set to true, set the samples per pixel to 1 for the first pass and double that number on each consecutive pass until cpu/gpu_samples_per_pixel is reached. This lets you get some faster feedback initially, because the image difference between the first passes is larger.
• undersampling - When enabled, return results before even 1 sample per pixel is accumulated. This gives you images at 1:8 resolution and then set above 0, start rendering at 1/(2^undersampling) resolution. So for example if the value is 4, sampling will start at 1/16 of the original resolution. When one pass is made at this resolution, the resolution is doubled and this repeats until the full resolution is reached. In our example this will return images sampled at 1:16 resolution and then 1:8, 1:4 and 1:2 (The images have the full resolution, but values are repeated for pixels that haven't been sampled). This is for faster feedback, but the images are highly pixelated.
• max_sample_level - If set above zero, stop rendering when this amount of samples per pixels is reached. This is set through the renderer object's constructor.
• max_render_time - If set above zero, stop after this many minutes (float number) have passed. This is set through the renderer object's constructor.
• noise_threshold - If set above zero, stop rendering when the noise difference between neighboring pixels falls below this threshold for all pixels. The unit used is defined by the internal noise-calculating algorithm (same as the thresholds in SettingsImageSampler). Values are usually between 0.001 and 0.1. This is set through the renderer object's constructor.
• max_draw_interval - Controls partial image updates if set above (the default) zero. This is the maximum time in milliseconds between image updates. So you get a potentially partial image update every time this time elapses. This lets the user see preliminary results earlier. The value in V-Ray for 3dsMax and Maya is 150.
• min_draw_interval - This is the minimum time between image updates. Set above zero if you want to limit the amount of drawing in the VFB or your own viewport. This may help with CPU and memory utilization when the rendering is very fast. The value in V-Ray for 3dsMax and Maya is 50.
• opencl_texsize - Despite the name, applies to both OpenCL and CUDA mode. This is the resolution to which textures are re-sampled if opencl_resizeTextures is true and the texture is larger than that. This is intended to help with limited GPU memory, but you may increase it from the default 512 to avoid losing detail if you have enough memory.
• opencl_resizeTextures - If true, apply opencl_texsize.
• opencl_textureFormat - Determines bit-depth of textures after reading into memory. 0=32-bit float, 1=16-bit float, 2=8-bit. Default is 16-bit.
• disable_render_elements - False by default. If set to true, no render elements will be calculated, which may save some computation and memory.

The render stops when any one of max_sample_level, max_render_time or noise_threshold is reached. If all are zero, the sampling goes on indefinitely.

6.11. Miscellaneous

The SettingsRaycaster plugin has one main parameter of interest:

...

• gi_dontRenderImage - Set to 1 if you're baking a GI prepass (Irradiance Map or Light Cache) file and want to skip the actual rendering.
• mtl_maxDepth - The maximum number of bounces to trace for reflections and refractions. Defaults to 5. Only increase if you need to. In RT mode set SettingsRTEngine::trace_depth instead.
• misc_transferAssets - Try to transfer missing assets in distributed rendering (DR) from the client to the render server. Disabled by default.

• misc_abortOnMissingAsset - Fail DR if an asset can't be found. Disabled by default.

• ray_max_intensity and ray_max_intensity_on - If you enable it with ray_max_intensity_on, ray_max_intensity clamps the values of some very bright samples to avoid the hard to clean up "firefly" artefacts at the cost of slightly wrong overall image brightness.
• num_probabilistic_lights and probabilistic_lights_on - (experimental) The number of lights to sample for probabilistic lighting if probabilistic_lights_on is true. Probabilistic lighting improves render speeds with hundreds and thousands of lights by only sampling a few of the "important" light sources.
• misc_lowThreadPriority - Render with low thread priority to improve multitasking. Disabled by default.

If you save the rendered image from the VFB and not from an AppSDK App SDK API, the corresponding Settings{JPEG|PNG|EXR|TIFF} plugin controls compression quality and bits per channel. You may need to change these according to your needs.

If you want to enable motion blur, set the SettingsMotionBlur plugin on parameter to 1. It also has the geom_samples parameter that affect quality, but may cost a lot of render time if increased. It should equal the number of geometry samples in the geometry data if it is non-static. Note that this plugin (SettingsMotionBlur) conflicts with CameraPhysical.

The SettingsLightLinker plugin allows you to define include or exclude lists for lights and objects, so that for example specific lights do not affect some objects etc. Refer to the plugin parameter metadata for explanations.

SettingsCaustics can enable improved rendering of caustic effects with photon mapping. This also requires setting some material parameters to make it work.

If you are not using CameraPhysical for depth of field, you can use SettingsCameraDof instead. Note that this plugin (SettingsCameraDof) conflicts with CameraPhysical.

• on - Set on - Set to true to enable DoF.
• aperture - The size of the camera aperture in scene units. Note that increasing this number corresponds to decreasing the physical camera's F-number.
• focal_dist - Distance from the camera to the focus plane in scene units.

7. Minimal renderable scene

This is a diagram of the most simple possible scene that will render an object. These are the plugins and parameters you will need to create and set.

Image Removed

A. Brief plugin reference

This reference does not list all of V-Ray's plugins, but most users will rarely need the ones that are not mentioned here.

Also only some of the parameters are explained here. As a general rule, follow the advice in Debugging and help when looking for info on plugins.

A.1. Common plugins

Light plugins (see also section 3 above)

LightOmni

• decay - The exponent for intensity decay. Default value is 2.0 which corresponds to the inverse square law.

LightSpot

• coneAngle - Full cone angle in radians.
• penumbraAngle - The size of an additional partly lit area around the cone in radians. If negative it's inside the cone.
• dropOff - Attenuation proportional to off-axis angle. Larger values dim the light toward the wide angles of the cone.
• falloffType - The type of transition in the penumbra region. 0 - linear; 1 - smooth cubic
• decay - The exponent for intensity decay. Default value is 2.0 which corresponds to the inverse square law.

LightRectangle

• noDecay - If set to true, light intensity will not fall off with distance. By default the inverse square law applies.
• doubleSided - Whether to emit light from the back sides of the rectangle.
• u_size - Width of the light in scene units.
• v_size - Length of the light in scene units.
• directional - Larger values make the light more concentrated along the +W axis in local UVW space.
• is_disc - True to round the rectangle to a disc (ellipse).
• rect_tex - A texture plugin to map onto the rectangle for light color.
• use_rect_tex - You also have to set this to true to actually use the rect_tex parameter.
• tex_resolution - The texture is actually resampled at this resolution. The default is 512, so even if you have a high resolution image, it may look pixelated if you don't increase this. This will consume more memory.

LightSphere

The .vrscene can store multiple cameras, where only one can be set as ‘renderable’ at a time. The rest of the cameras can be chosen for rendering, for example in V-Ray Standalone, by using the -camera command flag. This is useful, as oftentimes a project requires rendering different sequences from different cameras, while nothing else changes in the scene - a simple example would be to render two different views of the same visualization and in this way, the same scene can be rendered twice with V-Ray Standalone. An example scene with two cameras would have one them to render by default while the other will have dont_affect_settings flag raised.

In shading setups, textures can be projected from cameras. This can either be the same camera used for rendering, or another camera in the scene, used only for projecting a texture. In both cases, an extra SettingsCamera and RenderView plugin is exported for the camera projection with the dont_affect_settings flag raised. This is similar to the Multiple Cameras setup. In all cases, it’s a good idea to export one camera for rendering, and another one for the texture projection, even if it’s the same camera, as different properties apply for each.

7. Minimal renderable scene

This is a diagram of the most simple possible scene that will render an object. These are the plugins and parameters you will need to create and set.

Image Added

...

A. Brief plugin reference

This reference does not list all of V-Ray's plugins, but most users will rarely need the ones that are not mentioned here.

Also only some of the parameters are explained here. As a general rule, follow the advice in Debugging and help when looking for info on plugins.

A.1. Common plugins

Light plugins (see also section 3 above)

LightOmni

• decay - The exponent for intensity decay. Default value is 2.0 which corresponds to the inverse square law.

LightSpot

• coneAngle - Full cone angle in radians.
• penumbraAngle - The size of an additional partly lit area around the cone in radians. If negative it's inside the cone.
• dropOff - Attenuation proportional to off-axis angle. Larger values dim the light toward the wide angles of the cone.
• falloffType - The type of transition in the penumbra region. 0 - linear; 1 - smooth cubic
• decay - The exponent for intensity decay. Default value is 2.0 which corresponds to the inverse square law.

LightRectangle

• noDecay - If set to noDecay - If set to true, light intensity will not fall off with distance. By default the inverse square law applies.
• radius - Radius of the generated sphere in scene units.
• sphere_segments - Number of flat segments composing the sphere. Increase from the default 20 if you want a smoother shape.

LightMesh

• doubleSided - Whether to emit light from the back sides of the rectangle.
• u_size - Width of the light in scene units.
• v_size - Length of the light in scene units.
• directional - Larger values make the light more concentrated along the +W axis in local UVW space.
• is_disc - True to round the rectangle to a disc (ellipse).
• rect_tex - A texture plugin to map onto the rectangle for light color.
• use_rect
• noDecay - If set to true, light intensity will not fall off with distance. By default the inverse square law applies.
• doubleSided - Whether to emit light from the back sides of the triangles.
• geometry - A geometry plugin that will define the shape of the light. Note that complex geometries may make mesh lights slower and noisier.
• tex - A texture plugin to map onto the geometry for light color. This requires that the geometry plugin has valid UV data.
• use_tex - You also have to set this to true to actually use the rect_tex parameter.
• tex_resolution - The texture is actually resampled at this resolution. The default is 256512, so even if you have a high resolution image, it may look pixelated if you don't increase this. This will consume more memory.

LightDomeLightSphere

• noDecay - If set to true, light intensity will not fall off with distance. By default the inverse square law applies.
• radius - Radius of the generated sphere in scene units.
• sphere_segments - Number of flat segments composing the sphere. Increase from the default 20 if you want a smoother shape.

LightMesh

• noDecay - If set to true, light intensity will not fall off with distance. By default the inverse square law applies.
• doubleSided - Whether to emit light from the back sides of the triangles.
• geometry - A geometry plugin that will define the shape of the light. Note that complex geometries may make mesh lights slower and noisier.
• tex - A texture plugin to map onto the geometry for light color. This requires that the geometry plugin has valid UV data.
• use
• dome_spherical - Set to true to extend the dome to a full sphere. By default it is only a half-dome centered at the scene zenith. SettingsUnitsInfo::scene_upDir needs to be properly set.
• dome_tex - A texture plugin to use for IBL. Note that this usually requires spherical mapping.
• use_dome_tex - You also have to set this to true to actually use the dome_tex parameter.
• tex_resolution - The texture is actually resampled at this resolution. The default is 512256, so even if you have a high resolution image, it may look pixelated if you don't increase this. This will consume more memory.

LightIESLightDome

• iesdome_filespherical - Path Set to true to the file describing the light sourceextend the dome to a full sphere. By default it is only a half-dome centered at the scene zenith. SettingsUnitsInfo::scene_upDir needs to be properly set.
• dome_tex - A texture plugin to use for IBL. Note that this usually requires spherical mapping.
• use_dome_tex - You also have to set this to true to use the dome_tex.
• tex_resolution - The texture is actually resampled at this resolution. The default is 512, so even if you have a high resolution image, it may look pixelated if you don't increase this. This will consume more memory.

LightIES

• ies_file - Path to the file describing the light source
• filter_color - Use to tint the light. The default is white (1.0, 1.0, 1.0). Light color is defined by color temperature in the IES file.
• soft_shadows - Set to 0 (default) to cast hard shadows as point light; 1 to use the shape of the light for shadows; 2 to also use the shape for illumination
• power - Overrides the power specified in the file if > 0. The unit is lumens.
• ies_light_shape - Overrides the shape in the file if set to >= 0. Possible enumerated values: see table below.
• ies_light_width
• filter_color - Use to tint the light. The default is white (1.0, 1.0, 1.0). Light color is defined by color temperature in the IES file.
• soft_shadows - Set to 0 (default) to cast hard shadows as point light; 1 to use the shape of the light for shadows; 2 to also use the shape for illumination
• power - Overrides the power specified in the file if > 0. The unit is lumens.
• ies_light_shape - Overrides the shape in the file if set to >= 0. Possible enumerated values: see table below.
• ies_light_width - Used if ies_light_shape override is on.
• ies_light_length - Used if ies_light_shape override is on.
• ies_light_heightlength - Used if ies_light_shape override is on.
• ies_light_diameterheight - Used if ies_light_shape override is on.

• ies_light_diameter - Used if ies_light_shape override is on.

  shape

  shape

  	width	length	height	diameter
  0=point	0	0	0	0
  1=rectangle	>= 0	>= 0	0	0
  2=circle	0	0	0	< 0
  3=sphere	0	0	0	< 0
  4=vertical cylinder	0	0	> 0	< 0
  5=horizontal cylinder (length)	0	> 0	0	< 0
  6=horizontal cylinder (width)	> 0	0	0	< 0
  7=ellipse (length)	< 0	> 0	0	0
  8=ellipse (width)	> 0	< 0	0	0
  9=ellipsoid (length)	< 0	> 0	< 0	0
  10=ellipsoid (width)	> 0	< 0	< 0	0

SunLight

• transform - Similarly to the direct light plugin, the position doesn't matter as the light comes from infinity. The rotation matrix has to be set correctly, even though in theory the Sun is omnidirectional. The identity matrix results in light directed along the -Z axis, thus a noon Sun.
• target_transform - Currently doesn't make a difference. Don't leave uninitialized - set an identity transform.
• turbidity - See See VRaySun
• ozone - See VRaySunSee VRaySun
• water_vapour - See VRaySunSee VRaySun
• size_multiplier - See VRaySunSee VRaySun
• color_mode - See VRaySunSee VRaySun. Values  Values are 0, 1, 2 respectively for Filter, Direct, Override mode.
• intensity_multiplier - Relative intensity of the Sun (default 1.0). Try setting correct scales in SettingsUnitsInfo first.
• filter_color - Force a color tint. It's probably better to leave this white. See also the color_mode parameter.
• ground_albedo - Sky parameter, unused if there is no sky attached. Account for light reflected off an imaginary ground and scattered back in the sky. Default is (0.2, 0.2, 0.2).
• horiz_illum - Sky parameter, unused if there is no sky attached. Specifies the intensity (in lx) of the illumination on horizontal surfaces coming from the sky if sky_model is 1 or 2.
• sky_model - Sky parameter, unused if there is no sky attached. Selects the mathematical model approximating sky illumination. Values: 0=Preetham et al; 1=CIE Clear; 2=CIE Overcast; 3=Hosek et al.
• up_vector - Set to (0.0, 1.0, 0.0) if your scene up-axis is +Y to have correct lighting.
• invisible - Makes the Sun invisible to the camera and in reflections.

Geometry plugins

Node

• transform - World transformation applied to the geometry vertices which are defined in object space.
• geometry - Reference to a geometry source plugin, such as GeomStaticMesh for example.
• material - Reference to a material plugin. This should always be a MtlSingleBRDF. (Note that you can plug other Mtl plugins in the brdf slot of MtlSingleBRDF)
• visible - Set to false to disable the object. It will not be included in the raytracing intersection tree.

...

• mesh - The base mesh, usually a GeomStaticMesh.
• static_displacement - If set to true, the new generated triangles will be saved in the static rayserver tree. This will increase memory usage.
• use_globals - Whether to use the global settings from SettingsDefaultDisplacement. Default is true.
• view_dep - If use_globals is false, whether the amount of tesselation is view-dependent. The global default is true.
• edge_length - If the view-dependent option is on (globally or locally), this is the target edge size of the generated triangles in pixels. Otherwise it is in scene units.
• max_subdivs - If use_globals is false, the maximum number of triangle subdivisions for one original triangle of this mesh.
  For the rest of the parameters refer to VRayDisplacementMod.
• displacement_tex_color
• displacement_tex_float
• displacement_amount
• displacement_shift
• keep_continuity
• map_channel
• object_space_displacement
• use_bounds
• min_bound
• max_bound
• resolution
• precision

GeomHair

• TODO

GeomMeshFile

• file - Path to the vrmesh or abc file to load.
• object_path - When using Alembic, the starting object path string.

Material and BRDF plugins

MtlSingleBRDF

• TODO

Mtl2Sided

• TODO

MtlMulti

• TODO

MtlVRmat

• TODO

MtlGLSL

• TODO

MtlOSL

• TODO

MtlRoundEdges

• TODO

MtlMaterialID

• TODO

MtlOverride

• TODO

MtlRenderStats

• TODO

MtlWrapper

• TODO

BRDFVRayMtl

• TODO

BRDFBlinn

• TODO

BRDFCookTorrance

• TODO

BRDFGGX

• TODO

BRDFPhong

• TODO

BRDFWard

• TODO

BRDFDiffuse

• TODO

BRDFGlass

• TODO

BRDFGlassGlossy

• TODO

BRDFLight

• TODO

BRDFMirror

• TODO

BRDFCarPaint

• TODO

BRDFFlakes

• TODO

BRDFHair3

• TODO

BRDFLayered

• TODO

BRDFSSS2

• TODO

BRDFSSS2Complex

• TODO

BRDFScanned

• TODO

BRDFSkinComplex

• TODO

BRDFStochasticFlakes

• TODO

BRDFBump

• TODO

BRDFMultiBump

• of this mesh.
  For the rest of the parameters refer to VRayDisplacementMod.
• displacement_tex_color
• displacement_tex_float
• displacement_amount
• displacement_shift
• keep_continuity
• map_channel
• object_space_displacement
• use_bounds
• min_bound
• max_bound
• resolution
• precision

GeomHair

• TODO

GeomMeshFile

• file - Path to the vrmesh or abc file to load.
• object_path - When using Alembic, the starting object path string.TODO

Textures and UVWGenerators

TexSky

• sun - A reference to a SunLight instance. All sky parameters are taken from the Sun plugin, unless sun_dir_only is set to true.
• sun_dir_only - Only take the position and direction of the Sun. Use the TexSky parameters for everything else.

A.2. Other plugins

CameraDome

EffectLens

GeomParticleSystem

• mesh - A mesh plugin to use for some types of instances, depending on render_type.
• render_type - 3=multipoints; 4=multistreak; 6=points; 7=spheres; 8=sprites; 9=streak. The default is 7.
• colors - ColorList with a color for each particle.
• positions - VectorList with the particle positions.
• velocities - VectorList with velocities for motion blur. The values are in world units per frame.
  For the rest of the parameters for particular particle types, check the parameter list as described in Debugging and help.

VRayClipper

Volumetric plugins

The information from this page is also available at User Guide V-Ray Application SDK.