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These guidelines are for users of the 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 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. floatingpagetoc

1. Introduction

1.1. A note on terminology

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

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• 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 App SDK are IntList, FloatList, ColorList and VectorList.
• Generic heterogeneous lists: The App SDK uses a generic type class called Value for items in a generic list. 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).

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Apart from documentation included with the 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.

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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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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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