Basic parameters
Diffuse - this is the diffuse color of the
material. Note the actual diffuse color of the surface also depends on the
reflection and refraction colors. See the Energy
preservation parameter below.
Reflect - reflection color.
Fresnel reflections - checking this option
makes the reflection strength dependent on the viewing angle of the surface.
Some materials in nature (glass etc) reflect light in this manner. Note that
the Fresnel effect depends on the index of refraction as well.
Glossiness - controls the sharpness of
reflections. A value of 1.0 means perfect mirror-like reflection; lower
values produce blurry or glossy reflections. Use the
Subdivs parameter below to control the quality of glossy reflections.
Subdivs - controls the quality of glossy
reflections. Lower values will render faster, but the result will be more
noisy. Higher values take longer, but produce smoother results.
Use interpolation - VRay can use a
caching scheme similar to the irradiance map to speed up rendering of glossy
reflections. Check this option to turn caching on. See the Reflection
interpolation section for more details.
Max depth - the number of times a ray can
be reflected. Scenes with lots of reflective and refractive surfaces may
require higher values to look right.
Exit color - if a ray has reached its
maximum reflection depth, this color will be returned without tracing the
ray further.
Refract - refraction color. Note that the
actual refraction color depends on the reflection color as well. See the
Energy preservation parameter below.
IOR - index of refraction for the
material, which describes the way light bends when crossing the material
surface. A value of 1.0 means the light will not change direction.
Glossiness - controls the sharpness of
refractions. A value of 1.0 means perfect glass-like refraction; lower
values produce blurry or glossy reractions. Use the
Subdivs parameter below to control the quality of glossy refractions.
Subdivs - controls the quality of glossy
refractions. Lower values will render faster, but the result will be more
noisy. Higher values take longer, but produce smoother results. This
parameter also controls the quality of the translucent effect, if on (see
below).
Use interpolation - VRay can use a
caching scheme similar to the irradiance map to speed up rendering of glossy
refractions and translucency. Check this option to turn caching on. See the
Refraction interpolation section for more details.
Max depth - the number of times a ray can
be refracted. Scenes with lots of refractive and reflective surfaces may
require higher values to look right.
Exit color - if this is on, and a ray has
reached the maximum refraction depth, the ray will be terminated and the
exit color returned. When this is off, the ray will not be refracted, but
will be continued without changes.
Fog color - the attenuation of light as it
passes through the material. This option allows to simulate the fact that
thick objects look less transparent than thin objects. Note that the effect
of the fog color depends on the absolute size of the objects and is
therefore scene-dependent.
Fog multiplier - the strength of the fog
effect. Values above 1.0 are not recommended.
Affect shadows - this will cause the
material to cast transparent shadows, depending on the refraction color and
the fog color. This only works with VRay shadows and lights.
Affect alpha - this will cause the
material to transmit the alpha of the refracted objects, instead of
displaying an opaque alpha. Note that currently this works only with clear
(non-glossy) refractions.
Translucent - turning this on will make
the material translucent - being able to transport light below the material
surface. Note that refraction must be enabled for this effect to be visible.
The effect is also known as sub-surface scattering (SSS). Currently VRayMtl
supports only single-bounce scattering.
Thickness - this limits the rays that will
be traced below the surface. This is useful if you do not want or don't need
to trace the whole sub-surface volume.
Light multuplier - a multiplier for the
translucent effect.
Scatter coefficient - the amount of
scattering inside the object. 0.0 means rays will be scattered in all
directions; 1.0 means a ray cannot change its direction inside the
sub-surface volume.
Forward/backward coefficient - controls
the direction of scattering for a ray. 0.0 means a ray can only go forward
(away from the surface, inside the object); 0.5 means that a ray has an
equal chance of going forward or backward; 1.0 means a ray will be scattered
backward (towards the surface, to the outside of the object).
BRDF
The
BRDF parameters determine the type of the hilights and glossy reflections
for the material. There parameters have an effect only if the reflection
color is different from black and reflection glossiness is different than
1.0.
Type - this determines the type of BRDF
(the shape of the hilight):
Phong - Phong hilight/reflections
Blinn - Blinn hilight/reflections
Ward - Ward hilight/reflections
Anisotropy - determines the shape of the
hilight. A value of 0.0 means isotropic hilights. Negative and positive
values simulate "brushed" surfaces.
Rotation - determines the orientation of
the anisotropic effect in degrees (rotation in degrees).
Local axis - controls how the direction
for the anisotropic effect is chosen:
Local axis - the direction is based on the
selected local object axis.
Map channel - the direction is based on
the selected mapping channel.
Options
Trace reflections - if this is
off, reflections will not be traced, even if the
reflection color is greater than black. You can turn this off to produce
only hilights. Note that when this is off, the diffuse color will not be
dimmed by the reflection color, as would happen normally.
Trace refractions - if this is
off, refractions will not traced, even if the
refraction color is greater than black.
Cutoff - this is a threshold below which
reflections/refractions will not be traced. VRay tries to estimate the
contribution of reflections/refractions to the image, and if it is below
this threshold, these effects are not computed. Do not set this to 0.0 as it
may cause excessively long render times in some cases.
Double-sided - if this is true, VRay will
flip the normal for back-facing surfaces with this material. Otherwise, the
lighting on the "outer" side of the material will be computed always. You
can use this to achieve a fake translucent effect for thin objects like
paper.
Reflect on back side - if this is true,
reflections will be computed for back-facing surfaces too. Note that this
affects total internal reflections too (when refractions are computed).
Use irradiance map - if this is true, the
irradiance map will be used to approximate diffuse indirect illumination for
the material. If this is off, direct qmc GI will be used. You can use this
for objects in the scene which have small details and are not approximated
very well by the irradiance map.
Treat glossy rays as GI rays - this
specifies on what occasions glossy rays will be treated as GI rays:
Never - glossy rays are never treated as
GI rays.
Only for GI rays - glossy rays will be
treated as GI rays only when GI is being evaluated. This can speed up
rendering of scenes with glossy reflections and is the default.
Always - glossy rays are always treated as
GI rays. A side effect is that the Secondary GI engine will be used for
glossy rays. For example, if the primary engine is irradiance map, and
the secondary is light cache, the glossy rays will use the light cache
(which is a lot faster).
Energy preservation mode - determines how
the diffuse, reflection and refraction color affect each other. VRay tries
to keep the total amount of light reflected off a surface to be less that or
equal to the light falling on the surface (as this happens in the real
life). For this purpose, the following rule is applied: the reflection level
dims the diffuse and refraction levels (a pure white reflection will remove
any diffuse and refraction effects), and the refraction level dims the
diffuse level (a pure white refraction color will remove any diffuse
effects). This parameter determines whether the dimming happens separately
for the RGB components, or is based on the intensity:
RGB - this mode causes dimming to be
performed separately on the RGB components. For example, a pure white
diffuse color and pure red reflection color will give a surface with
cyal diffuse color (because the red component is already taken by the
reflection).
Monochrome - this mode causes dimming to
be performed based on the intensity of the diffuse/reflection/refraction
levels.
Maps
These determine the various texture maps used by the material.
Reflect interpolation
These determine the options for the interpolation of glossy reflections.
They are very similar to the options for the irradiance map. Note that it is
not recommended to use interpolation for animations, since this may cause
severe flickering.
Refract interpolation
These determine the options for the interpolation of glossy reflections.
They are very similar to the options for the irradiance map. Note that it is
not recommended to use interpolation for animations, since this may cause
severe flickering.
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