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


General Terms


Analytic sampling

This is one of 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 takes in consideration all triangles crossing a given ray during a given time interval. Keep in mind that because of its precision this method is extremely slow on high-poly scenes with fast motion. (See also: Motion blurQuasi Monte Carlo sampling)

Anti-aliasing  

Related terms: 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  

Related terms: 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  

BRDF

Related terms: 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 GGX, Phong, Blinn, and Ward BRDF types. BRDF settings can be found with the V-Ray Material.

BSP Tree

Related terms: BSP, 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

Related terms: 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

Related terms: 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 appear 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 utilizing of all available computational resources (usually all machines in a local network). 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. (See also: DR Tab)

Adaptive Sampling 

Related terms: Early Termination

Early termination (or adaptive sampling) 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-aliasingImage Sampler)

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 image 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.


MaterialIndex
Vacuum1.00000
Air at STP1.00029
Ice1.31
Water at 20 C1.33
Acetone1.36
Ethyl alcohol1.36
Sugar solution(30%)1.38
Fluorite1.433
Fused quartz1.46
Glycerin1.473
Sugar solution (80%)1.49
Typical crown glass1.52
Crown glasses1.52-1.62
Spectacle crown, C-11.523
Sodium chloride1.54
Polystyrene1.55-1.59
Carbon disulfide1.63
Flint glasses1.57-1.75
Heavy flint glass1.65
Extra dense flint, EDF-31.7200
Methylene iodide1.74
Sapphire1.77
Heaviest flint glass1.89
Diamond2.417


Indirect Illumination (GI)  

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 rendering 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 IlluminationArea lights , Area shadows)

Low Accuracy Computations

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

(Quasi) Monte Carlo Sampling  

Related terms: DMC (Deterministic Monte Carlo), QMC (Quasi Monte Carlo), Monte Carlo

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, 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 samplingMonte Carlo sampling)

Photon Map

Related terms: Photon

This is a simulation of real world photons (light particles). To produce effects like caustics, 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 rendering so that highly realistic caustic effects are produced.

Reflections

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

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 ray tracer, 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 image, without introducing bias.

Translucency

Translucency is a term describing the interaction of light with a non-opaque medium (wax, marble, skin, etc.). V-Ray supports various translucency models that can produce natural results. Translucency options are found in the V-Ray Material, and specialty materials like FastSSS2, AlSurface or the 2-Sided material.


Key V-Ray Terms


Subdivs

In V-Ray, subdivs is a measure for the maximum amount of samples (rays) that V-Ray uses 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 for sampling a glossy reflection is 4, V-Ray will never make more than 4 x 4 = 16 samples to evaluate the reflection.


Distributed Rendering

A rendering method of dividing frames (images) into regions (buckets) and rendering them on different render nodes (machines) by using V-Ray DR spawner or V-Ray render server. (See also: Distributed rendering)

Network Rendering

A method for letting each render node (machine) render an entire frame (image), for example by submitting jobs to job managers like Backburner.

Render Node

A machine that performs the actual rendering.

V-Ray SDK

A low-level software development kit used for creating custom V-Ray materials and geometry.


V-Ray App SDK

A high-level software development kit, allowing control over V-Ray’s feature set. Useful for integrating V-Ray into any application or for creating and editing V-Ray data in an automated way.

VRIMG

VRIMG is Chaos's proprietary image file format. It is 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 can be used as the rendering output format, 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 V-Ray Standalone or referenced as an asset into any application that has V-Ray integrated.