Dirt 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.
Unoccluded Color – Specifies the color that will be returned by the texture for unoccluded areas. A texture map can be used for this parameter.
Occluded Color – Specifies the color that will be returned by the texture for occluded areas. A texture map can be used for this parameter.
Radius – Specifies the amount of area (in scene units) where the Dirt effect is produced. A texture can be used to control the radius. The texture intensity is multiplied by the radius to calculate the final radius at a given surface point. If the texture is white at a given surface point, the full radius value is used. If the texture is black, a radius of 0.0 is used.
Distribution – Forces the rays to gather closer to the surface normal. The effect is that the dirt area is 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.
Falloff – Controls the speed of the transition between occluded and unoccluded areas. For more information, please see the Falloff Parameter example below.
Self-occlusion only – Enables the object to be occluded only by itself. No other object in the scene occludes the self-occluded object.
Ignore self-occlusion – When enabled, the object will not occlude itself. It will still be occluded by other objects in the scene.
Invert Normals – When enabled, the dirt effect is reversed with respect to surface normals - e.g. instead of crevices, open corners will be shaded with the occluded color. For more information, please see the Invert Normals example below.
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).
Ignore for GI – When enabled, the dirt effect will not be taken into consideration for GI calculations. For more information, please see the Ignore for GI example below.
Use Transparency – When enabled, Dirt will take into account the opacity of the occluding objects. This can be used, for example, to calculate ambient occlusion from opacity-mapped trees etc. When disabled (the default), occluding objects are always assumed to be opaque. Note that working with correct opacity is slower, since Dirt must examine and evaluate the material on the occluding objects.
Environment Occlusion – When this option is switched on V-Ray will use the environment when calculating the occlusion of areas that are not occluded by other objects.
Reflection Occlusion – Enables or disables the Reflection Occlusion.
BRDF – Specifies the procedural mode that will be used to generate the VRayDirt texture.
Reflection Occlusion (Phong)
Reflection Occlusion (Blinn)
Reflection Occlusion (Ward)
Glossiness – Controls the spread of the rays traced for reflection occlusion. A texture map can be used for this parameter.
Affect Reflection Elements – When enabled, the ambient reflection will affect the reflection render elements. This can be used to create reflection masks.
Bias X – Provides bias to the normals on the X-axis, so that the dirt effect is forced in this direction. Consider that the parameter can also take negative value for inverting the direction of the effect.
Bias Y – Provides bias to the normals on the Y-axis, so that the dirt effect is forced in this direction. Consider that the parameter can also take negative value for inverting the direction of the effect.
Bias Z – Provides bias to the normals on the Z-axis, so that the dirt effect is forced in this direction. Consider that the parameter can also take negative value for inverting the direction of the effect.
Mode – Specifies the multiplication mode of the colors.
Multiplier – Multiplies the RGB numbers for each pixel of the top layer with the RGB number of the corresponding pixel from the bottom layer. The result is a darker picture.
Blend Amount – Takes each pixel from the top layer if present. Otherwise the bottom layer is used.
Unoccluded Color – Controls the intensity of the Unoccluded color.
Occluded Color – Controls the intensity of the Occluded color.
Example: Falloff Parameter
Example: Ignore for GI
This check-box determines whether the dirt effect is going to be visible during the GI calculation.
Ignore for GI: on
Ignore for GI: off
Example: Same Objects Only
Same objects only: on
Example: Invert Normals
A bitmap is used in the texmap radius slot. Notice that the main radius parameter still has effect - it determines the amount of area where the texmap radius bitmap would blend.
Invert Normal: off
Invert Normal: on