V ray material

3/20/2016 VRay Material | VRayMtl VRay 3.3 for 3ds Max Chaos Group Help

http://docs.chaosgroup.com/display/VRAY3MAX/VRay+Material+%7C+VRayMtl#VRayMaterial|VRayMtlExample:TheRoughnessParameter 1/19

V-Ray Material | VRayMtl

Page Contents

VRayMtl OverviewDiffuse ParametersRe㰀謄ectionRefraction

Example: The Roughness ParameterExample: The Re㰀謄ection Color ParameterExample: The Re㰀謄ection Glossiness ParameterExample: The Fog Multiplier Parameter

TranslucencySelf-IlluminationBRDFOptions

Example: Fog System Units ScalingRe㰀謄ect InterpolationRefract Interpolation

Notes

VRayMtl Overview

A special material – the VRayMtl - is provided with the V-Ray renderer. This allows for better physically correctillumination (energy distribution) in the scene, faster rendering, and more convenient re㰀謄ection and refractionparameters. Within the VRayMtl you can apply different texture maps, control the re㰀謄ections and refractions, addbump and displacement maps, force direct GI calculations, and choose the BRDF for the material.

Diffuse Parameters



Diffuse – this is the diffuse color of the material. Note the actual diffuse color of the surface also depends onthe re㰀謄ection and refraction colors. See the Energy preservation parameter below.

Roughness – this parameter can be used to simulate rough surfaces or surfaces covered with dust (forexample, skin, or the surface of the moon). For more information, see The Roughness Parameter examplebelow.

Re㰀謄ection

Re㰀謄ect – re㰀謄ection color. Note that the re㰀謄ection color dims the diffuse surface color based on the Energypreservation option. For more information, see The Re㰀謄ection Color Parameter example below.

Fresnel Re㰀謄ections – checking this option makes the re㰀謄ection strength dependent on the viewing angle of thesurface. Some materials in nature (glass, etc.) re㰀謄ect light in this manner. Note that the Fresnel effect dependson the index of refraction as well.



Fresnel IOR – the IOR to use when calculating Fresnel re㰀謄ections. Normally this is locked to the Refraction IORparameter, but you can unlock it for ἀ渄ner control. For more information, see The Fresnel Option example below.

Highlight glossiness – this determines the shape of the highlight on the material. Normally this parameter islocked to the Re㰀謄ection glossiness value in order to produce physically accurate results.

Re㰀謄ection glossiness – controls the sharpness of re㰀謄ections. A value of 1.0 means perfect mirror-like re㰀謄ection;lower values produce blurry or glossy re㰀謄ections. Use the Subdivs parameter below to control the quality ofglossy re㰀謄ections. For more information, see The Re㰀謄ection Glossiness Parameter example below.

Subdivs – controls the quality of glossy re㰀謄ections. Lower values will render faster, but the result will be morenoisy. Higher values take longer, but produce smoother results.

Dim distance – speciἀ渄es a distance after which the re㰀謄ection rays will not be traced.

Dim fall off – a fall off radius for the dim distance.

Affect Channels – Allows you to specify which channels are going to be affected by the re㰀謄ection of thematerial

Color Only – the re㰀謄ection will affect only the RGB channel of the ἀ渄nal render Color+alpha – this will cause the material to transmit the alpha of the re㰀謄ected objects, instead ofdisplaying an opaque alpha. All channels – all channels and render elements will be affected by the re㰀謄ections of the material.

Max depth – the number of times a ray can be re㰀謄ected. Scenes with lots of re㰀謄ective and refractive surfacesmay require higher values to look right.

Exit color – if a ray has reached its maximum re㰀謄ection depth, this color will be returned without tracing the rayfurther.

Refraction

Refract – refraction color. Note that the actual refraction color depends on the re㰀謄ection color as well. For moreinformation, see The Refraction Color Parameter example below.

IOR – index of refraction for the material, which describes the way light bends when crossing the materialsurface. A value of 1.0 means the light will not change direction. For more information, see The Refraction IORParameter example below.

Glossiness – controls the sharpness of refractions. A value of 1.0 means perfect glass-like refraction; lowervalues produce blurry or glossy refractions. Use the Subdivs parameter below to control the quality of glossyrefractions. For more information, see The Refraction Glossiness Parameter example below.

Subdivs – controls the quality of glossy refractions. Lower values will render faster, but the result will be morenoisy. Higher values take longer, but produce smoother results. This parameter also controls the quality of thetranslucent effect, if on (see below).



Use interpolation – V-Ray can use a caching scheme similar to the irradiance map to speed up rendering ofglossy refractions and translucency. Check this option to turn caching on. For more information, see TheRefraction Depth Parameter example below.

Max depth – the number of times a ray can be refracted. Scenes with lots of refractive and re㰀謄ective surfacesmay 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 theexit color returned. When this is off, the ray will not be refracted, but will be continued without changes. Formore information, see The Refraction Exit Color Parameter example below.

Fog color – the attenuation of light as it passes through the material. This option allows the user to simulate thefact that thick objects look less transparent than thin objects. Note that the effect of the fog color depends onthe absolute size of the objects and is therefore scene-dependent unless the Fog system units scaling isenabled. The fog color also determines the look of the object when using translucency. For more information,see The Fog Color Parameter example below.

Fog multiplier – the strength of the fog effect. Smaller values reduce the effect of the fog, making the materialmore transparent. Larger values increase the fog effect, making the material more opaque. In more preciseterms, this is the inverse of the distance at which a ray inside the object is attenuated with am amount equal tothe Fog color. For more information, see The Fog Multiplier Parameter example below.

Fog bias – this parameter allows the user to change the way the fog color is applied; by adjusting thisparameter, you can make thin parts of the object to appear more transparent or less transparent than normal.

Affect shadows – this will cause the material to cast transparent shadows, depending on the refraction colorand the fog color. This only works with V-Ray shadows and lights.

Affect Channels – Allows you to specify which channels are going to be affected by the transparency of thematerial

Color Only – the transparency will affect only the RGB channel of the ἀ渄nal render Color+alpha – this will cause the material to transmit the alpha of the refracted objects, instead ofdisplaying an opaque alpha. Note that currently this works only with clear (non-glossy) refractions. All channels – all channels and render elements will be affected by the transparency of the material

Dispersion – this option enables the calculation of true light wavelength dispersion. For more information, seethe Dispersion example below.

Abbe – this option allows you to increase or decrease the dispersion effect. Lowering it widens the dispersionand vice versa.

Example: The Roughness Parameter

This example demonstrates the effect of the Roughness parameter. Note how, as the Roughness increases, the



materials appears more "㰀謄at" and dusty.

Roughness = 0.0 (regular diffuse material)

Roughness = 0.3 Roughness = 0.6

Example: The Re㰀謄ection Color Parameter

This example demonstrates how the Re㰀謄ection color parameter controls the re㰀謄ectivity of the material. Notethat this color also acts as a ἀ渄lter for the diffuse color (e.g. stronger re㰀謄ections dim the diffuse component).

Re㰀謄ection color = Black. (0, 0, 0)

Re㰀謄ection color = Medium Gray. (128, 128, 128)

Re㰀謄ection color = White. (255, 255, 255)



Example: The Fresnel Option

This example demonstrates the effect of the Fresnel option. Note how the strength of the re㰀謄ection varies withthe IOR of the material. For this example, the Re㰀謄ection color is pure white (255, 255, 255).

Fresnel = On IOR = 1.3



Fresnel = Off.

Example: The Re㰀謄ection Glossiness Parameter

This example demonstrates how the Re㰀謄ection glossiness and Highlight glossiness parameters control thehighlights and re㰀謄ection blurriness of the material.

Re㰀謄ection/Highlight Glossiness = Re㰀謄ection/Highlight Glossiness = Re㰀謄ection/Highlight Glossiness =



1.0 (perfect mirror re㰀謄ections)

0.8 0.6

Example: The Refraction Color Parameter

This example demonstrates the effect of the Refraction color parameter to produce glass materials. For theimages in this example, the material has a gray Diffuse color, white Re㰀謄ection color, and the Fresnel option isturned on.

Refraction color = Black (0, 0, 0)

no refraction

Refraction color = Light Gray (192, 192, 192)

Refraction color(255, 255, 255)

Example: The Refraction IOR Parameter

This example demonstrates the effect of the Refraction IOR parameter. Note how light bends more as the IORdeviates from 1.0. When the index of refraction (IOR) is 1.0, the render produces a transparent object. Notehowever, that in the case of transparent objects, it might be better to assign an opacity map to the material,rather than use refraction.



Refraction IOR = 0.8 Refraction IOR = 1.0 Refraction IOR = 1.3 Refraction IOR = 1.8

Example: The Refraction Glossiness Parameter

This example demonstrates the effect of the Refraction glossiness parameter. Note how lower Refractionglossiness values blur the refractions and cause the material to appear as frosted glass.

Refraction glossiness = 1.0 Refraction glossiness = 0.9 Refraction glossiness = 0.8

Example: The Refraction Depth Parameter

This example demonstrates the effect of the Refraction depth parameter. Note how too low of a refraction depthproduces incorrect results. Also, in the last two examples, note how areas with total internal re㰀謄ection are alsoaffected by the Re㰀謄ection depth.



Refractiondepth = 1 Re㰀謄ectiondepth = 5





Example: The Refraction Exit Color Parameter

This example demonstrates the effect of the refraction Exit color parameter. This is mostly useful to show areasof deep refractions in the image, or for materials needing higher refraction depth. Note how the red areas arereduced when the Re㰀謄ection depth and Refraction depth are increased.

Refraction Exit color = Off Re㰀謄ection depth = 5 Refraction depth = 5

Refraction Exit color = On Refraction Exit color = Red

(255, 0, 0) Re㰀謄ection depth is 5 Refraction depth is 5

Refraction Exit color = On Re㰀謄ection depth = 8 Refraction depth = 8



Example: The Fog Color Parameter

This example demonstrates the effect of the Fog color parameter. Notice how the thick areas of the object aredarker in the two images on the right because of the light absorption of the fog.

Fog color = White (255, 255, 255)

no light absorption

Fog color = Gray (243, 243, 243)

Fog color = Green (230, 243, 213)

Example: The Fog Multiplier Parameter

This example demonstrates the effect of the Fog multiplier parameter. Smaller values cause less lightabsorption because of the fog; while higher values increase the absorption effect.



Fog multiplier = 0.5 Fog multiplier = 1.0 Fog multiplier = 1.5

Example: Dispersion

This example demonstrates the Dispersion capabilities of the V-Ray material and the effect of the Abbeparameter.

Dispersion = Off Dispersion = On Abbe = 10

Dispersion = On Abbe = 50



Translucency

Type – selects the algorithm for calculating translucency (also called sub-surface scattering). Note thatrefraction must be enabled for this effect to be visible. Currently only single-bounce scattering is supported. Thepossible values are:

None – no translucency is calculated for the material;Hard (wax) model – this model is speciἀ渄cally suited for hard materials like marble; Soft (water) model – this model is mostly for compatibility with older V-Ray versions (1.09.x); Hybrid model – this is the most realistic sss model and is suitable for simulating skin, milk, fruit juice andother translucent materials.

Back-side color – normally the color of the sub-surface scattering effect depends on the Fog color; thisparameter allows you to additionally tint the SSS effect.

Thickness – this limits the rays that will be traced below the surface. This is useful if you do not want or do notneed to trace the whole sub-surface volume.

Light multiplier – a multiplier for the translucent effect.

Scatter coefἀ渄cient – the amount of scattering inside the object. 0.0 means rays will be scattered in alldirections; 1.0 means a ray cannot change its direction inside the sub-surface volume.

Forward/backward coefἀ渄cient - controls the direction of scattering for a ray. 0.0 means a ray can only goforward (away from the surface, inside the object); 0.5 means that a ray has an equal chance of going forwardor backward; 1.0 means a ray will be scattered backward (towards the surface, to the outside of the object).

Self-Illumination

Self-Illumination – controls the emission of the surface.

GI – when enabled, the self-illumination affects global illumination rays and allows the surface to cast light onnearby objects. Note however, that it may be more efἀ渄cient to use area lights or VRayLightMtl material for thiseffect.

Multiplier – a multiplier for the self-illumination effect. This is useful if you need to boost the self-illuminationvalues so that the surface produces stronger illumination with GI.

BRDF



BRDF parameters determine the type of the highlights and glossy re㰀謄ections for the material. The parametershave an effect only if the re㰀謄ection color is different from black and re㰀謄ection glossiness is different than 1.0.

Type – this determines the type of BRDF (the shape of the highlight):

Phong – Phong highlight/re㰀謄ections Blinn – Blinn highlight/re㰀謄ections Ward – Ward highlight/re㰀謄ections Microfacet GTR (GGX) – GGX highlight/re㰀謄ections

Options

Trace re㰀謄ections – if this is off, re㰀謄ections will not be traced, even if the re㰀謄ection color is greater than black.You can turn this off to produce only highlights. Note that when this is off, the diffuse color will not be dimmedby the re㰀謄ection 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 re㰀謄ections/refractions will not be traced. V-Ray tries to estimate thecontribution of re㰀謄ections/refractions to the image, and if it is below this threshold, these effects are notcomputed. Do not set this to 0.0 as it may cause excessively long render times in some cases.



Environment priority – this speciἀ渄es how to determine the environment to use if a re㰀謄ected or refracted ray goesthrough several materials each of which has an environment override.

Double-sided – if this is checked, V-Ray will 㰀謄ip 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 afake translucent effect for thin objects like paper.

Re㰀謄ect on back side – if this is checked, re㰀謄ections will be computed for back-facing surfaces too. Note thatthis affects total internal re㰀謄ections too (when refractions are computed).

Use irradiance map – if this is checked, the irradiance map will be used to approximate diffuse indirectillumination for the material. If this is off, brute force GI will be used in which case the quality of the brute forceGI is determined by the Subdivs parameter of the Irradiance Map. You can use this for objects in the scenewhich have small details and are not approximated very well by the irradiance map.

Fog system units scaling – when enabled, the fog color attenuation becomes dependent on the current systemunits. For more information, see Fog System Units Scaling example below.

Override material effect – if this is checked, Effect ID can be used to input values for Material ID.

Treat glossy rays as GI rays – this speciἀ渄es 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 uprendering of scenes with glossy re㰀謄ections and is the default. Always – glossy rays are always treated as GI rays. A side effect is that the Secondary GI engine will beused 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, re㰀謄ection, and refraction color affect each other. V-Raytries to keep the total amount of light re㰀謄ected off a surface to be less than or equal to the light falling on thesurface (as this happens in the real life). For this purpose, the following rule is applied: the re㰀謄ection level dimsthe diffuse and refraction levels (a pure white re㰀謄ection will remove any diffuse and refraction effects), and therefraction level dims the diffuse level (a pure white refraction color will remove any diffuse effects). Thisparameter determines whether the dimming happens separately for the RGB components or is based on theintensity:

RGB – this mode causes dimming to be performed separately on the RGB components. For example, apure white diffuse color and pure red re㰀謄ection color will give a surface with cyan diffuse color (becausethe red component is already taken by the re㰀謄ection). Monochrome – this mode causes dimming to be performed based on the intensity of thediffuse/re㰀謄ection/refraction levels. For more information, see The Energy Preservation Mode Parameter example below.

Opacity mode – this parameter controls how the opacity map works. The possible values are:

Normal – in this mode, the opacity map is evaluated as normal, the surface lighting is computed and theray is continued for the transparent effect. The opacity texture is ἀ渄ltered as normal. Stochastic – in this mode, the surface is randomly shaded as either fully opaque or fully transparent so thaton average it appears to be with the correct transparency. This mode reduces lighting calculations butmight introduce some noise in areas where the opacity map has gray-scale values. The opacity texture is



still ἀ渄ltered as normal. Clip – in this mode, the surface is shaded as either fully opaque or fully transparent depending on the valueof the opacity map (i.e. without any randomness). This mode also disables the ἀ渄ltering of the opacitytexture. This is the fastest mode, but it might increase 㰀謄ickering when rendering animations. For more information, see the Opacity mode parameter example below.

Example: Fog System Units Scaling

This example demonstrates the usage of the Fog system units scaling check box. The teapot in the scene has aradius of four meters. When the Fog system units scaling is disabled we can see through the teapot. Howeverwhen we enable the Fog system units scaling the real size of the object is taken into consideration and we cansee that the light is absorbed to a much greater extent.

Fog system units scaling = Off Fog system units scaling = On



Example: The Energy Preservation Mode Parameter

This example demonstrates how the Energy preservation mode controls the way re㰀謄ections dim the diffusecolor.

Energy Preservation = RGB.


Energy Preservation = RGB.

Re㰀謄ection color = Medium Green. (0, 128, 0)

Energy Preservation = Monochrome.


Energy Preservation = Monochrome.

Re㰀謄ection color = Medium Green. (0, 128, 0)



Example: Opacity mode parameter

Normal opacity. Because the opacitytexture is ἀ渄ltered the result is nice

and smooth but very slow.

Stochastic opacity. The texture isstill ἀ渄ltered, so the result is smooth

but render times are greatlyimproved.

Clip opacity. The texture is forcedto black or white; the render time is

very fast, but result is sharperwhich may increase 㰀謄ickering in

animation.

The renders below show a blow-up of the tree to better show the effect of the different modes. Note that in the

ἀ渄rst two renders the opacity is blurry because of the texture ἀ渄ltering.



Normal opacity. Because the textureis ἀ渄ltered, this makes the normal-

sized render smoother and reduces㰀謄ickering in animation, but the render

time is very slow.

Stochastic opacity. The texture isstill ἀ渄ltered, which keeps the

normal-sized render smooth, andthe render time is much better.

Clip opacity. Because the opacitymap is forced to either full black or

white, the result is sharp. Therender time is very good, but the

increased sharpness can increase㰀謄ickering in animations.

Maps

These determine the various texture maps used by the material.

Re㰀謄ect Interpolation



These determine the options for the interpolation of glossy re㰀謄ections. They are very similar to the options forthe irradiance map. Note that it is not recommended to use interpolation for animations, since this may causesevere 㰀謄ickering.

Refract Interpolation

These determine the options for the interpolation of glossy re㰀謄ections. They are very similar to the options forthe irradiance map. Note that it is not recommended to use interpolation for animations, since this may causesevere 㰀謄ickering.

Notes

Use the VRayMtl whenever possible in your scenes. This material is speciἀ渄cally optimized for V-Rayand often GI and lighting is computed much faster for V-Ray materials than for standard 3ds Maxmaterials. Many V-Ray features (e.g. light cache, photon mapping, render elements) are guaranteedto work properly only with VRayMtl and other V-Ray compliant materials.VRayMtl can produce re㰀謄ections/refractions for matte objects – see Wrapper Material |VRayMtlWrapper.

http://docs.chaosgroup.com/display/VRAY3MAX/Light+Cache

http://docs.chaosgroup.com/display/VRAY3MAX/Photon+Mapping

http://docs.chaosgroup.com/display/VRAY3MAX/Render+Elements

http://docs.chaosgroup.com/display/VRAY3MAX/Wrapper+Material+%7C+VRayMtlWrapper

V ray material

Documents

Transcript of V ray material