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Analytic sampling
This is one of the VRay'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 "perfection"
this method will be extremely slow on high-poly scenes with fast motion. (See
also:
Motion blur parameters, Motion blur, Quasi Monte Carlo sampling)
Antialiasing (Image sampling)
Antialiasing is a special technique for producing smooth images of
high-contrast edges and small details in materials and objects. VRay achieves antialiasing by taking additional image samples where necessary. To determine if
more samples are needed, VRay compares differences in color (and/or other
properties) of neighboring image samples.. This comparison can be performed in
several ways. VRay supports fixed, simple 2 level and adaptive
antialiasing (See also: Image samplers parameters, G-Buffer, G-Buffer Antialiasing)
Area lights
Area light is a term describing a non-point light source. These types of
light sources produce area shadows. VRay supports rendering of area
lights through VRayLight. (See also: VRayLight parameters, 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). VRay is capable of
producing the effect of area shadows either through VRayShadow or through
area lights. (See also:
VRayShadow parameters, Area lights)
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. VRay supports the following BRDF types: Phong, Blinn,
Ward. (See also:
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 VRay
implements two types of BSP Tree. These are a static BSP Tree for
scenes without motion blur and a motion blur BSP Tree. (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. (See also:
Caustics parameters)
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. (See also:
DOF parameters,
Camera parameters)
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 VRay makes the most out of your equipment when rendering a single
frame. For animation sequences however, you should use MAX's standard network
rendering as it may be more efficient. (See also: Bucket,
Distributed rendering)
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 VRay 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 parameters, Antialiasing,
Image samplers parameters)
G-Buffer Antialiasing
VRay is capable of antialiasing the rendered image based on the differences
in one or several G-Buffer channels. (See also: Antialiasing,
Image sampler parameters, G-Buffer)
HDRI (High Dynamic Range Image)
A High Dynamic Range Image is an image containing high-dynamic range 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 samping
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 VRay 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. To achieve a material with a specific IOR
you have to set the Index of refraction field value in MAX's standard
materials in the section Extended parameters.
| Material |
Index |
| Vacuum |
1.00000 |
| Air at STP |
1.00029 |
| Ice |
1.31 |
| Water at 20 C |
1.33 |
| Acetone |
1.36 |
| Ethyl alcohol |
1.36 |
| Sugar solution(30%) |
1.38 |
| Fluorite |
1.433 |
| Fused quartz |
1.46 |
| Glycerin |
1.473 |
| Sugar solution (80%) |
1.49 |
| Typical crown glass |
1.52 |
| Crown glasses |
1.52-1.62 |
| Spectacle crown, C-1 |
1.523 |
| Sodium chloride |
1.54 |
| Polystyrene |
1.55-1.59 |
| Carbon disulfide |
1.63 |
| Flint glasses |
1.57-1.75 |
| Heavy flint glass |
1.65 |
| Extra dense flint, EDF-3 |
1.7200 |
| Methylene iodide |
1.74 |
| Sapphire |
1.77 |
| Heaviest flint glass |
1.89 |
| Diamond |
2.417 |
Indirect Illumination (Global lighting, Global Illumination)
In 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:
Indirect Illumination parameters, Irradiance map)
Irradiance map
Indirect Illumination in VRay is generally achieved by calculating GI
samples. The irradiance map is a special cache where VRay keeps precalculated
GI samples. During the rendering process when VRay 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 parameters, Indirect Illumination, Area lights, Area
shadows)
Low accuracy computations
In certain cases VRay will not need to compute absolutely precisely a ray
contribution to the final image. VRay will then use faster but less precise
methods for computation and will take fewer samples. This produces slightly
noisier results, but decreases rendering times. Users can control the degree of
optimization by changing when VRay switches to Low accuracy computations by
changing Degrade depth values. (See also: Degrade depth, Low subdivs)
(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 uses points forming a low-discrepancy sequence, which are more
evenly distributed than purely random ones. This is the method used by VRay to
evaluate complex things like global illumination, blurry reflections, depth of
field, motion blur and image antialiasing.
Motion Blur
This effect is observed when looking at some 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. (See also:
Motion Blur parameters, Analytic sampling, Monte Carlo sampling)
Photon, Photon map
This is a simulation of a real world photons (a photon is a light particle).
In order to produce caustics effects VRay 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 VRay supports accurate reflections. Glossy
reflections are as well supported (See also: VRayMap parameters,
VRayMtl parameters, Glossiness, Reflections, VRayMtl)
Refractions
Refraction is the bending of a wave when it enters a medium where it's 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 VRay supports true accurate refractions.
VRay also handles glossy refractions (See also:
VRayMap parameters,
VRayMtl parameters, IOR, Translucency, Glossiness, Reflections, VRayMtl)
Russian roulette
This is a technique for..?
Subdivs
In VRay subdivs is a measure for the maximum
amount of samples (rays) that VRay 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, VRay 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.). VRay supports a simple translucency model that
can nevertheless produce quite natural results. (See also:
VRayMap parameters,
VRayMtl parameters, Refractions)
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