Glossary

This page contains a glossary of common terms used in V-Ray.

 

General Terms

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Analytic sampling 

This is one of the V-Ray's techniques for calculating motion blur. Instead of taking a number of time samples, the analytic method blurs the moving triangles perfectly. It will take in consideration all triangles crossing a given ray during a given time interval. Keep in mind that because of its precision this method will be extremely slow on high-poly scenes with fast motion. (See also: Motion blur, Quasi Monte Carlo sampling)

Anti-aliasing (Image Sampling)   

Anti-aliasing is a special technique for producing smooth images of high-contrast edges and small details in materials and objects. V-Ray achieves anti-aliasing by taking additional image samples where necessary. To determine if more samples are needed, V-Ray compares differences in color (and/or other properties) of neighboring image samples. This comparison can be performed in several ways. V-Ray supports fixed, simple 2 level, and adaptive anti-aliasing. Anti-aliasing settings can be found under V-Ray's Image Sampler settings. (See also: G-Buffer Anti-aliasing)

Area lights (Rectangle light)   

An area light is a non-point light source. These types of light sources produce area shadows. V-Ray supports rendering of area lights through VRayLight. (See also: Area shadows)

Area shadows (Soft shadows)   

Area shadows are blurred shadows (or shadows with blurred edges) that are caused by non-point light sources (Area lights). V-Ray is capable of producing the effect of area shadows either through VRayShadow or through area lights. (See also: Area lights)

Further reading: Ray Traced Shadows | VRayShadow for 3ds Max

BRDF (Bi-Directional Reflectance Distribution Function)

One of the most general means to characterize the reflection properties of a surface is by use of the bi-directional reflection distribution function (BRDF), a function which defines the spectral and spatial reflection characteristic of a surface. V-Ray supports the following BRDF types: Phong, Blinn, Ward and GGX. BRDF settings can be found with the VRayMtl.

BSP (BSP Tree, Binary Space Partitioning Tree)

BSP is special data structure for organizing scene geometry in order to speed up ray-triangle intersections (intersecting a ray with the triangles in the scene is the task most frequently performed by a raytracer). Currently, V-Ray implements two types of BSP Tree. These are a static BSP Tree for scenes without motion blur and a motion blur BSP Tree. V-Ray also uses the Intel Embree raycaster to accelerate raycasting. (See also: Motion Blur)

Bucket (Region, Rendering region)

A bucket is a rectangular part of the current frame that is rendered independently from other buckets. The division of a frame into rendering regions allows for optimal resource utilization (CPUs, PCs, memory). It also allows for distributed rendering. (See also: Distributed Rendering)

Caustics (Radiosity)

This is the effect of light refracted by a non-opaque object hitting a (diffuse) surface.

Depth of field (DOF)

Depth of field is the effect of having a particular point in the scene to appear focused (sharp) and the rest to out of focus (blurry) depending on camera shutter properties and the distance from the camera. This is similar to how real world cameras work so this effect is especially useful for producing photorealistic images. Depth of field settings are usually found under the V-Ray Camera.

Distributed rendering (DR)   

Distributed rendering is a technique for utilization of all available computational resources (all CPUs in a machine, all machines in a LAN, etc.). DR divides the currently processed frame into rendering regions and keeps all CPUs in LAN-connected machines busy computing the rendering result. Overall DR assures that V-Ray makes the most out of your equipment when rendering a single frame. 
3ds Max: For animation sequences, the standard network rendering should be used as it may be more efficient.

Further Reading: Set up Distributed Rendering for 3ds Max, Maya

Early termination 

Early termination is a technique for reducing the samples taken for evaluating a blurry value. This basically works by looking at the samples as they are computed one by one and deciding, after each new sample, if more samples are required. Early termination is used throughout V-Ray for all blurry values. (See also: Importance sampling)

G-Buffer

This term describes the collection of various data generated during image rendering. These could be Z-values, material IDs, object IDs, non-clamped colors, etc. This has proven to be very useful for performing post-rendering image processing. (See also: G-Buffer Anti-aliasing, Image Sampler)

Further Reading: G-Buffer Support for 3ds Max

G-Buffer Anti-aliasing   

V-Ray is capable of anti-aliasing the rendered image based on the differences in one or several G-Buffer channels. (See also: Anti-aliasing)

HDRI (High Dynamic Range Image)

A High Dynamic Range Image is an image containing a high-dynamic range of colors (with components exceeding the range 0.0-1.0, or 0-255). This type of images is often used as an environment map to light the scene with natural light.

Importance sampling 

Importance sampling is a technique for basing the number of samples required for evaluating a blurry value, on the effect that value has on the final result. For example, dark materials require fewer samples for evaluating GI than bright materials; dim area lights can do with less samples than bright lights etc. Importance sampling is used throughout V-Ray for all blurry values. (See also: Early termination)

Index of Refraction (IOR)

The index of refraction is defined as the speed of light in vacuum divided by the speed of light in a given medium. IOR = C/V, where V is the light speed specific for the different mediums. 
3ds Max: To achieve a material with a specific IOR, set the Index of refraction field value in Max's standard materials in the section Extended parameters.

 

 

Indirect Illumination (Global lighting, Global Illumination, GI)   

In the real world, when a particle ray of light hits an object, it produces multiple reflected rays with different intensity in all directions. These rays on their turn may hit some other objects and produce even more rays and so on. This process, multiply repeated, generates the so-called Global Illumination. (See also: Irradiance Map)

Further reading: Classification of GI Methods

Irradiance map   

Indirect Illumination in V-Ray is generally achieved by calculating GI samples. The irradiance map is a special cache where V-Ray keeps precalculated GI samples. During the rendering process when V-Ray needs a particular GI sample, it computes it by interpolating the nearest precalculated GI samples stored in the irradiance map. Once computed, the Irradiance map can be saved in a file and reused in subsequent renderings. This can be especially useful for camera fly-through animations. Samples for VRayLight can also be stored in the irradiance map. (See also:  Indirect Illumination, Area lights , Area shadows)

Low accuracy computations

In certain cases, V-Ray will not need to compute a ray contribution to the final image with absolute precision. V-Ray will then use faster but less precise methods for computation and will take fewer samples. This produces slightly noisier results, but decreases rendering times. 

(Quasi) Monte Carlo sampling   

Monte Carlo sampling is a method for numerical computation of integrals of functions by evaluating these functions at a number of random points. Quasi Monte Carlo sampling is a modification of this method, which instead of randomly generated points, it uses points forming a low-discrepancy sequence, which are more evenly distributed than purely random ones. This is the method used by V-Ray to evaluate complex effects such as global illumination, blurry reflections, depth of field, motion blur and image anti-aliasing.

Motion Blur   

This effect is observed when looking at a fast-moving object. The motion is so fast that one can not focus the object, and the object's image appears blurred to the viewer. Motion Blur parameters can usually be found under the V-Ray Camera settings. (See also: Analytic sampling, Monte Carlo sampling)

Photon, Photon map

This is a simulation of a real world photons (light particles). In order to produce caustics effects, V-Ray traces certain amount of photons that come out of the light sources. Then the results are stored in a photon map and used during the rendering process so that highly realistic caustic effects are produced.

Reflections

As an advanced raytracer, V-Ray supports accurate reflections. Glossy reflections are as well supported.

Refractions

Refraction is the bending of a wave when it enters a medium where its speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media. As an advanced raytracer, V-Ray supports true accurate refractions. V-Ray also handles glossy refractions. 

Russian roulette

This is a technique for reducing variance (i.e. noise) by eliminating computationally intensive paths with little or no contribution to the final picture, without introducing bias.

Subdivs

In V-Ray, subdivs is a measure for the maximum amount of samples (rays) that V-Ray will use to compute a certain value. The maximum number of samples is proportional to the square of the subdivs value. For example, if the subdivs value of a glossy reflection is 5, V-Ray will never make more than 5 x 5 = 25 samples to evaluate the reflection.

Translucency

Translucency is a term describing the interaction of light with a non-opaque medium (wax, marble, skin, etc.). V-Ray supports a simple translucency model that can nevertheless produce quite natural results. Translucency is involved with V-Ray Reflect and Refract Maps, V-Ray Material | VRayMtl, and Refractions.

 

Key V-Ray Terms

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Distributed Rendering

A rendering method of dividing frames to buckets and rendering them on different render nodes by using V-Ray DR spawner, V-Ray Standalone or a V-Ray RT render server. (See also: Distributed rendering)

Network Rendering

A rendering method of rendering whole frames on each render node, for example by submitting jobs to job managers like Backburner.

Render Node

A machine that performs the actual rendering.

V-Ray DR spawner

A V-Ray tool used to start 3ds Max in server mode for Distributed Rendering.

V-Ray SDK

A V-Ray Software Development Kit used for creation of custom materials and geometry.

VRIMG File

VRIMG is a Chaos proprietary file format used by the V-Ray Frame Buffer to store the rendered image incrementally (bucket by bucket) while rendering in full floating-point format, with all available render elements. It is used as a render output but it is not recommended to use it as a texture file format. VRIMG contains metadata, i.e. render statistics. It supports dynamic bucket size. VRIMG can be saved just as any other image format – it can either be the render output format or it can be saved from the VFB.

 

vrscene File

The .vrscene file format is a text file that uses UTF-8 encoding (without BOM) and can be exported from all platforms that use V-Ray. It contains all the information about the scene such as geometry, lights and shaders, and can be rendered with the V-Ray Standalone. This functionality can transfer lights and entire assets with their textures and materials between V-Ray platforms, while animation is also included.