VRayDirt Overview


The VRayDirt is a texture map that can be used to simulate a variety of effects, for example dirt around the crevices of an object, or to produce an ambient occlusion pass.

VRayDirt Parameters


Ignore for GI  - this check-box determines whether the dirt effect will be taken into consideration for GI calculations or not.




Example: Ignore for GI

This check-box determines whether the dirt effect is going to be visible during the GI calculation.

All the examples are rendered using a VRayMtl with a VRayDirt Map in the Diffuse channel:

ignore for GI: on

ignore for GI: off

Example: Consider Same Object Only

consider same object only: on

Invert normal  - this option allows to revert the effect with respect to surface normals - e.g. instead of crevices, open corners will be shaded with the occluded color.

Example: Invert Normal

In the next example 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

Environment occlusion  - when this option is checked V-Ray will use the environment when calculating the occlusion of areas that are not occluded by other objects.

Affect Reflection  - when checked the ambient reflection will affect the reflection render elements. This can be used to create reflection masks

Ignore Self Occlusion  - when this option is on the object will not occlude itself. It will still be occluded by other objects in the scene.

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 other objects  - when on, the dirt will affect only the objects themselves, without including contact surfaces and edges. If off, the entire scene geometry is participating for the final result.

Use Transparency  - when onVRayDirt 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 off (the default), occluding objects are always assumed to be opaque. Note that working with correct opacity is slower, since in that case VRayDirt must examine and evaluate the material on the occluding objects.

Black  - this is the color that will be returned by the texture for occluded areas. You can also use a texture map for this parameter.

Glossiness  - this parameter controls the spread of the rays traced for reflection occlusion. You can also use a texture map for this parameter.

White  - this is the color that will be returned by the texture for unoccluded areas. You can also use a texture map for this parameter.

Subdivs  - controls the number of samples that V-Ray takes to calculate the dirt effect. Lower values render faster but produce a more noisy result.

Example: Subdivisions Parameter 

subdivisions: 1

subdivisions: 5

subdivisions: 20

Mode  - Allows you to specify the procedural mode that will be used to generate the  VRayDirt  texture.

  • 0 - Ambient occlusion
  • 1 - Phong reflection occlusion
  • 2 - Blinn reflection occlusion 
  • 3 - Ward reflection occlusion

Radius  - this parameters determines the amount of area (in scene units) where the VRayDirt effect is produced. You can also use a texture to control the radius.

Example: Radius Parameter

This parameters determines the amount of area (in units) where the VRayDirt effect is produced. Notice that two of the object do not contact any other objects on their tops, so there is no dirt effect.

Simple VRayMtl - no Dirt effect

radius: 10.0

radius: 30.0

Example: Texmap Radius

In the next example, 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.


radius: 100
texmap radius: bitmap


radius: 300
texmap radius: bitmap

Falloff  - this parameter controls the speed of the transition between occluded and unoccluded areas.

Example: Falloff Parameter

falloff: 0.0

falloff: 1.0

falloff: 5.0

Bias (X,Y,Z)  - these parameters will bias the normals to the X (Y,Z) axes, so that the dirt effect is forced to those directions. Consider that these parameter can also take negative values for inversing the direction of the effect

Example: Bias

These parameters will bias the normals, so that the dirt effect is forced to some of the axis(es).

bias_X: 100.0

bias_Y: 100.0

bias_Z: 100.0

Distribution  - this parameter will force 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.

Example: Distribution Parameter

This parameter will force the rays to gather closer. The effect is that the dirt area is being narrowed closer to the contact edges.

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