Please note that this documentation space offers information for V-Ray 3.6! For most up-to-date documentation, refer to V-Ray Next for Modo help.

This page contains information about the V-Ray Dirt Texture in V-Ray for Modo.

 

Page Contents

 

Overview


V-Ray Dirt Texture is a texture map that can be used to simulate a variety of effects such as dirt around the crevices of an object. It can also be used to produce an ambient occlusion pass.

 

 


 

UI Path: ||Shading viewport|| > Shader Tree > Add Layer button > V-Ray Textures > V-Ray Dirt

 

Parameters





Unoccluded color
– The color that will be returned by the texture for unoccluded areas. A texture map can also be used for this parameter.

Occluded color– The color that will be returned by the texture for occluded areas. A texture map can also be used for this parameter.

Radius – Determines the amount of area (in scene units) where the V-Ray Dirt effect is produced. A texture can be used to control the radius. For more information, see Example: Radius Parameter.

Distribution – Determines the distribution of the dirt effect. Larger values force the rays to gather closer to the surface normal, giving the effect of the dirt area being narrowed closer to the contact edges. For ambient occlusion, set this parameter to 1.0 to get distribution similar to the ambient lighting on a diffuse surface. Negative distribution values make the dirt spread out more intensely. For more information, see Example: Distribution Parameter.

Falloff – Controls the gradualness or suddenness of the transition between occluded and unoccluded areas. For more information, see Example: Falloff Parameter.

Bias (X, Y, Z) – These values bias the normals to the X, Y or Z axes so that the dirt effect is forced to those directions. Consider that these parameters can also take negative values for inverting the direction of the effect. For more information, see Example: Biases.

Ignore For Gi – When enabled, the dirt effect will not be taken into consideration for GI calculations. For more information, see Example: Ignore for GI/ Consider Same Objects Only.

Consider Same Object Only – When enabled, the dirt will affect only the objects themselves, without including contact surfaces and edges. If disabled, all scene geometry participates the final result. For more information see Example: Consider Same Object Only.

Invert Normal – When disabled, the rays are traced outside the surface, and when enabled the rays are traced inside the surface. This means the effect can be reversed with respect to surface normals. For example, when this option is enabled, open corners (and not crevices) will be shaded with the occluded color. For more information, see Example: Invert Normal.  

Double Sided – When enabled, the rays needed to generate the dirt map will be shot from both sides of the faces (both in the direction of the normals and in the opposite direction).

Work With Transparency – When enabled, V-Ray Dirt will take into account the opacity of the occluding objects. This can be used, for example, if you want to calculate ambient occlusion from opacity-mapped trees etc. When disabled (the default), occluding objects are always assumed to be opaque. Note that enabling this option can cause render time to increase since V-Ray Dirt must examine and evaluate the material on the occluding objects.

Ignore Self Occlusion – When enabled, the object will not occlude itself. It will still be occluded by other objects in the scene.

Mode – Specifies the mode in which the dirt map is going to be calculated.

Ambient occlusion – Normal ambient occlusion will be calculated.
Reflection occlusion (Phong, Blinn, Ward)
– Reflection occlusion will be used. The difference between ambient and reflection occlusion is basically in the direction in which rays are traced. With ambient occlusion, rays are traced in all directions uniformly; with reflection occlusion, the direction depends on the viewing direction (just as when calculating reflections) and the spread of the rays depends on the Reflection glossiness and BRDF type used.

Environment Occlusion – When enabled, V-Ray will use the environment when calculating the occlusion of areas that are not occluded by other objects. When enabled and Mode is Phong, Blinn, or Ward, occlusion will be added to the reflection render element.

Glossiness – Controls the spread of the rays traced for reflection occlusion. A value of 1 means that just a single ray is traced (just like when tracing clear reflections) and smaller values make the spread of the traced rays.

Exclude Objects – Selects an object or group that will not be shaded by the V-Ray Dirt map. Multiple objects can be linked simultaneously to the Exclude objects channel in Schematic setup.

Include Child Items – When enabled, all child objects of those selected for Exclude Objects will be considered as well.

As Inclusive list – When enabled, the meaning of the Exclude Objects list is reversed; only objects in the list will be shaded by the V-Ray Dirt map.

Use Texture For Excluded – When enabled, excluded objects will be rendered with the texture or color specified for Unoccluded color.

Result AffectObjects – Specifies a list of objects that will affect the calculation of the V-Ray Dirt map. Excluded objects will be considered "invisible" for the calculations of the V-Ray Dirt map. Multiple objects can be linked simultaneously to the Result Affect Objects channel in Schematic setup.

Include Child Items – When enabled, all child objects of those selected for Result Affect Objects will be considered as well.

As Inclusive List – When enabled, the meaning of the Result Affect Objects list is reversed. When enabled, this list is an inclusion list. When disabled, the list is an exclusion list.

Subdivs per AA Sample – Controls the number of samples that V-Ray takes to calculate the dirt effect for each AA sample made by the Image Sampler. Lower values render faster but produce a more noisy result. This parameter works independently from the Use Local Subdivs parameter in the DMC Sampler, so changes will affect the scene even if Use local subdivs is disabled. For more information, see Example: The Subdivisions Parameter.

 



Example: Radius Parameter

 

This parameter determines the amount of area where the VRayDirt effect is produced. In the following example, the Dirt color has been tinted red to clarify the effect and uses meters for the Radius because of the scene scale.


 


Simple V-Ray Material – no Dirt effect 

 


Radius
: 50.0m

 


Radius: 100.0m

 

 

 

This parameter determines the amount of area (in units) where the V-Ray Dirt effect is produced. Notice that two of the objects do not contact any other objects on their tops, so there is no dirt effect. All the examples are rendered using a V-Ray Material with a V-Ray Dirt map in the Diffuse slot. 

 

 


 

Example: Distribution Parameter

 

In the following example, the Dirt color has been tinted red to clarify the effect and uses meters for the Radius of 100m.

 

 

Rays distribution (X,Y,Z) axis
Equal angle between rays distribution
Distribution parameter = 0.0  

Rays distribution (X,Y,Z) axis
Different angle between rays distribution
Distribution parameter > 0.0  

 

 


Distribution
: 1.0

 


Distribution
: 3.0

 


Distribution
: 10.0

 

 

 

When increased, distribution forces the rays to gather closer. The effect is that the dirt area is forced closer to the contact edges.

 

 


 

Example: Falloff Parameter

 

In the following example, the Dirt color has been tinted red to clarify the effect and uses meters for the Radius of 100m.

 

 


Falloff
: 0.0

 


Falloff
: 1.0

 


Falloff
: 10.0

 

 

 

 


 

Example: Subdivisions Parameter

 

In the following example, the Dirt color has been tinted red to clarify the effect and uses meters for the Radius of 100m.

 

 

Subdivs: 1

 

Subdivs: 5

 

Subdivs: 20

 

 

 

 



Example: Biases


These parameters bias the normals so that the dirt effect is forced to one or more axes.

 

 



Bias X: 100.0

 


Bias Y: 100.0

 


Bias Z: 100.0

 

 

 

 

 


 

Example: Ignore for GI

 

The Ignore for Gi option determines whether the dirt effect is going to be visible during the GI calculation. In the following example, the Dirt color has been tinted red to clarify the effect and uses a Radius of 751mm.

 

 


Ignore for Gi: Enabled

 


Ignore for Gi: Disabled

 

 

 

 


 

Example: Consider Same Object Only


 

Consider Same Object Only: enabled

 


Consider Same Object Only: Disabled

 

 


 

 

 


 

Example: Invert Normal


The Invert Normal option will change the direction of tracing the rays. When it is disabled the rays are traced outside the surface; when enabled, the rays are traced inside the surface.

 

 

 
Invert Normal: Disabled

 

 
Invert Normal: Enabled

 

 

V-Ray Dirt Radius Texture


The Radius Texture slot of V-Ray Dirt is visible in Modo's Schematic viewport and allows controlling the texture's radius.


The user can control the Radius Texture Multiplier by tuning the Low / High value channels of the connected texture.

 

V-Ray Dirt Occluded Color boundary boost tip


V-Ray Dirt's occluded color boundaries can be made more pronounced by manipulating the Linear HDR RGB channel.

 

 

First, open the example scene attached above.

Open V-Ray Dirt's Occluded Color Picker from Modo's interface and modify the RGB (Linear HDR) color parameter(s) to a higher value, for example 10.

 


Render and observe the difference.

 

 

 
RGB Only

 

 
With RGB (Linear HDR) modification