--- title: "Dirt" canonical: "https://documentation.chaos.com/space/LAV/125306336/Dirt" format: markdown --- This page provides information about the Dirt texture in Chaos Vantage. Overview Dirt 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. Dirt Main Radius – Determines the amount of area (in scene units) where the Dirt effect is produced. A texture can be used to control the radius. See the Radius and Colors example below. Occluded Color – The color that is returned by the texture for occluded areas. A texture map can be used for this parameter. See the Radius and Colors example below. Unoccluded Color – The color that is returned by the texture for unoccluded areas. A texture map can be used for this parameter. See the Radius and Colors example below. 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. The Distribution parameter works with  Inner occlusion ,  Ambient occlusion , and  Ambient + inner occlusion  modes. For ambient occlusion, set this parameter to 1.0 to get distribution similar to the ambient lighting on a diffuse surface. See the Distribution example below. Falloff – Controls the speed of the transition between occluded and unoccluded areas.  Bias x/y/z – These parameters bias the normals to the (X, Y, 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.   Streaks ambient – Draws streaks across dirt effect respective to ambient occlusion. Streaks blur – Gives ability to blur the streaks. Bare in mind that the new algorithm is calculating this effect, and the visual representation of the streaks is different.  Blur – Controls the amount of the blur of the streaks. Streaks size – Controls the thickness of all streaks.  Streaks density – Controls the density of the streaks.  Dirt Options Ignore bump – Excludes bump maps from Dirt computations. The option is useful, when the bump effect is too strong and may produce undesirable effects such as holes. Consider same object on – When enabled, the dirt affects only the objects themselves, without including contact surfaces and edges. If off, the entire scene geometry is participating for the final result.  Invert normal – When enabled, dirt is traced inside the surface instead of the default outside. This reverses the dirt effect with respect to the surface normals — for example, instead of crevices, open corners are shaded with the occluded color. Affect alpha – When enabled, the texture automatically receives an alpha component from the generated dirt distribution and this way makes the unoccluded area of the Dirt map transparent. When disabled, the alpha values from the maps used in Occluded and Unoccluded color slots are applied.  Double sided – When enabled, rays are traced both in the direction of the normal and in the opposite direction. This creates an effect where both crevices and edges are occluded.  Work with transparency – When enabled, Dirt takes 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 (by default), occluding objects are always assumed to be opaque. Note that working with correct opacity is slower, since, in that case, Dirt must examine and evaluate the material on the occluding objects. Ignore self occlusion – When enabled, objects are not able to occlude themselves. Mode – Specifies how the same objects to be considered. You can choose from Ambient occlusion, Phong reflection occlusion, Blinn reflection occlusion, Ward reflection occlusion, Inner occlusion, and Ambient + inner occlusion. Ambient occlusion – Normal ambient occlusion is calculated. Reflection occlusion (Phong, Blinn, Ward) – Reflection occlusion is 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 while 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. Inner occlusion – Inverts the effect with respect to surface normals - e.g. instead of crevices, open corners are shaded with the occluded color. This mode changes the direction of tracing the rays. When this mode is selected, the rays are traced inside the surface, otherwise, they are traced outside the surface. For more information, see Inner Occlusion example below. Ambient + inner occlusion – A combination of Ambient occlusion and Inner occlusion modes used for enhanced weathering effect. Environment occlusion – When enabled, Vantage uses the environment when calculating the occlusion of areas that are not occluded by other objects. 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), smaller values make the spread of the traced rays. Available when the Occlusion Mode is Reflection occlusion (Phong, Blinn, Ward). Screen space radius – When screen space radius is on, the radius set in Dirt main settings is calculated based on screen pixels and not in scene units.  Examples The following examples demonstrate the effect that individual Dirt Texture parameters have on the scene. Click on any image to view it at a higher resolution.  Example: Radius and Color In this example, the goal is to recreate the natural weathering of a golden dragon statue using the Radius , Occluded Color , and Unoccluded Color parameters. The Occluded Color defines the patina finish, accentuating the crevices and recessed areas of the geometry. The Radius controls the scale and intensity of this effect, determining how pronounced and widespread the patina appears across the surface. The Unoccluded Color sets the overall color of the statue. Here, a VRayMtl is used and the Dirt texture is mapped to its Diffuse color parameter. The Occluded Color of the Dirt texture is green, and the Unoccluded Color is yellow. The metallic effect is achieved through the Metalness and Reflection glossiness parameters of the VRayMtl. Raidus is 0 so there is no dirt effect Raidus is 1 Raidus is 100 Example: Distribution The Distribution parameter forces the rays to gather closer. The effect is that the dirt area is being narrowed closer to the contact edges. Here, a VRayMtl is used and the Dirt texture is mapped to its Diffuse color parameter. The Dirt Mode is set to Ambient + inner occlusion. The Occluded Color is green, and the Unoccluded Color is yellow. 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 = 0 Distribution = 5 Distribution = 20