This page provides some details on the settings available for the BRDFStochasticFlakes material node.

 

Overview


The V-Ray Stochastic Flakes material can be used to simulate car paints, snow and other glittery materials. It works by simulating at render time the aggregated effect of a large number of mirror-like flakes scattered over the surface of an object. The material is somewhat similar to the Car Paint materials, but uses less memory and avoids the tiling issues for these materials. The term stochastic means "using a random variable".

 

UI Paths


 

||mat Network|| > V-Ray > Material > V-Ray Stochastic Flakes

||out Network|| > V-Ray Render Element node > V-Ray > Material > V-Ray Stochastic Flakes

 

 

Nodes


The BRDFStochasticFlakes node provides inputs for controlling various material properties. They correspond to parameters in the section below.

 

 

Parameters




Enable Flakes – When enabled, the material simulates flakes scattered on the surface of the object. When disabled, the underlying smooth distribution is used. See the Enable Flakes example below.

Number of Flakes – The number of flakes, expressed as the square root of the actual number of flakes in the unit texture square. For example, a value of 3000 generates 9,000,000 flakes in the unit texture square. The number of flakes is restricted to 231 (a little over 2 billion), which means the highest useful value for Number of Flakes is 46340. If you need more than 2 billion flakes, increase the Flake Scale parameter. See the Number of Flakes example below.

Hilight Glossiness – Controls the distribution of the flakes. Values close to 1.0 orient all flakes with normals pointing more perpendicular to the surface, whereas lower values randomize the normals of the flakes. See the Hilight Glossiness example below.

Blur Angle – Controls the "softening" of the flakes effect. Higher values produce softer results, while smaller values make the flakes sharper. Usually, value between 0.5 and 8 are used. See the Blur Angle example below.

Subdivs – Controls the number of samples to use when calculating reflections. Note that this parameter is available for changing only when Use Local Subdivs is enabled in the DMC Sampler.

Reflect Filter – Specifies the reflection color of the flakes.

Mapping Type – Specifies the way the flakes are scattered on the surface:

Mapping Channel – The flakes are mapped according to the specified mapping channel. The density of the flakes on the surface depends on the way the UVs follow the surface. 
Triplanar Object XYZ 
– The material uses triplanar mapping to create the flakes. This mode is useful for objects that don't have suitable UV mapping.

Flake Scale – Controls the scale of the texture space. When Mapping Type is set to Mapping Channel, a value of 1.0 is recommended. For Triplanar Object XYZ mapping, the Number of Flakes amount is distributed in each square unit in local object coordinates. In this case it is necessary to lower the Flake Scale value to 0.05, 0.01, or even less, and increase the Number of Flakes value depending on the object size, especially if square artifacts are observed.

Brdf Type – Specifies the BRDF used to guide the distribution of the flakes:

GGX – Uses GGX distribution for the flakes (the GGX distribution has a longer "tail" compared to Beckmann).
Beckmann – Uses a Beckmann distribution for the flakes.

 Seed – The seed for the randomization of flakes. Changing this value produces different flake patterns.

Method – Dropdown to enable Colored Flakes:

Off – No variance to the specified color for the flakes is applied. 
Random Hue 
– Enables randomized hue for the flakes. 
Random from Map
 
– Enables use of a texture map for randomized colors.

Random Saturation – When enabled, generates random saturation for each flake color.

Saturation – Specifies the saturation variation of the colors for all flakes when Random Saturation is disabled.

Random Lightness – When enabled, generates random lightness for each flake color.

Lightness – Specifies the lightness variation of the colors for all flakes when Random Lightness is disabled.

White Average – When enabled, renders colored flakes without the darkening effect. Note that this is not physically correct.

Random Color – Available when Method is set to Random from Map. Specifies a texture from which random colors are sampled and applied to the flake color.

Tex Subdivs – Specifies the subdivision of a unit square in texture space. Increase the value only if you observe square-like artifacts in zoomed regions.

Blend Min – Specifies the number of flakes per pixel, below which the smooth distribution is not computed and blended. When the number of flakes per pixel is above this value, the material gradually transitions into a smooth (non-discrete) BRDF.

Blend Max – Specifies the number of flakes per pixel, above which only the smooth distribution is computed. If the number of flakes per pixel is below this value, the material gradually transitions into discrete flakes.

 


Example: Enable Flakes

 

The Enable Flakes parameter allows the user to turn the Stochastic Flakes effect on and off. When on, flakes are scattered across the surface of the material. When off, the material renders with only the specified Brdf Type and Hilight Glossiness. In the example below, the BRDF type is set to GGX. Click on the image to open the full-res.

 

 
OFF
ON

 



Example: Number of Flakes

 

 

 Num Flakes = 2236 (5,000,000 flakes per unit texture square)

 Num Flakes = 7070 (50,000,000 flakes)

 Num Flakes = 22360 (500,000,000 flakes)

 

 

 

 

Example: Highlight Glossiness

 

 Hilight Glossiness = 0.6

 Hilight Glossiness = 0.8

 Hilight Glossiness = 0.95

Example: Blur Angle

 

 Blur Angle = 1.0

 Blur Angle = 3.0

 Blur Angle = 6.0

 




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