V-Ray Dirt guide: Create controlled contact shadows in 3ds Max

What will you learn in this guide?

V-Ray Dirt is a texture map that produces dirt-like shading in surface crevices and areas where surfaces touch other objects. It can also be used to create an ambient occlusion pass. In architectural visualization, this map can help make wall-floor junctions, furniture contacts, and model recesses stand out more clearly in an image.

This guide covers how VRayDirt works, its commonly used parameters, and limitations to consider when rendering on the GPU. Treat the settings not as fixed values that suit every scene, but as controls to test according to your model’s scale and the look you want to achieve.

Requirements and preparation

• Software: This guide focuses on using V-Ray Dirt in 3ds Max. Chaos’s relevant documentation does not specify a minimum V-Ray version or account requirements.

• Version note: According to Chaos’s release information, V-Ray 7 update 5 (7.50.00) was released on 5 November 2026. This release changed Include/Exclude Layers and IDs support for VRayDirt; this does not mean that this version is required for the basic settings in this guide to work.

• Scene: Since Radius uses scene units, take your object dimensions and scene units into account. The sources do not recommend a specific measurement standard.

• Hardware: The sources do not specify requirements for a particular processor, graphics card, or amount of memory. If you plan to use V-Ray GPU, see the compatibility notes below.

In Chaos’s examples, VRayDirt is used in a VRayMtl’s Diffuse channel. Starting with a simple material setup like this makes it easier to distinguish the map’s effect on the image. Rather than giving an unverified menu path, check the relevant map connection in the interface for your version of 3ds Max and V-Ray.

Setting up V-Ray Dirt step by step

1. Set up a simple test scene. Connect VRayDirt to a VRayMtl’s Diffuse channel and render a test frame that includes contact areas. Starting with a small number of objects makes it easier to see which surfaces affect one another.

2. Choose an effect mode. Ambient occlusion produces the standard ambient occlusion look. Inner occlusion traces rays inward from the surface, so the effect can become more pronounced on open corners rather than in crevices. Ambient + inner occlusion combines the two approaches. Compare the modes on the same part of the scene to determine which look you need. K1 also lists modes that produce reflection occlusion and streaks.

3. Adjust Radius to the scene scale. Radius sets the effect’s reach around a surface in scene units. As a result, the same value may not produce the same width of effect in two scenes built to different scales. Start with a low value and test in small increments; if the effect spreads too widely, reduce Radius.

   You can also connect a texture to the Radius input. In this case, the texture’s brightness is used to determine the local area of effect: white areas retain the main Radius value, while black areas reduce the local radius to zero. This lets you vary the effect across a surface.

4. Test Distribution and Falloff separately. Distribution changes how rays are concentrated relative to the surface normal. As the value increases, the effect gathers more around contact edges. Chaos shows a value of 1.0 as a reference example for ambient occlusion; treat it as a starting point for comparison, not a universal recipe. Falloff changes the transition between occluded and unoccluded areas. Adjust the two settings one at a time so you can see the visual difference.

5. Adjust colors and affected objects. Occluded Color sets the color returned for occluded areas, while Unoccluded Color sets the color for unoccluded areas. Texture maps can also be used for both parameters. When Consider Same Object Only is enabled, the map considers only the object itself; when disabled, other geometry in the scene can also contribute to the result. Ignore Self Occlusion prevents an object from occluding itself; other objects can still produce an effect.

6. Balance image cleanliness with Subdivs. Subdivs determines the number of samples used in the calculation. Fewer samples can shorten render time, but may make the image look grainier. If a clean result is important, test by increasing the value. Chaos documentation also notes that lowering the Noise threshold in Image Sampler can help clean up the result.

7. Use advanced options when needed. Bias X, Y, and Z let you direct the effect along specific axes; negative values can reverse the direction. Double Sided makes rays trace in both directions of the surface normal. Thin mode is available only in Inner occlusion mode and reduces the effect on thin surfaces. Test these controls one at a time to see how each setting contributes to the result.

Common mistakes and GPU compatibility

Setting Radius without accounting for scene scale: Because Radius uses scene units, values cannot be transferred directly between projects. Instead of copying a value, check the effect’s width using the dimensions of the scene itself.

Treating a quick test as final quality: A low Subdivs setting can make a render faster, but it may also increase noise. Make your final decision based on a cleaner test rendered under the conditions you’ll use for the final image.

Assuming every option works the same way on the GPU: Chaos’s 3ds Max documentation states that Ignore Self Occlusion is not supported by V-Ray GPU. Streaks blur and Streaks density are also among the options not supported on the GPU. If your target look depends on these features, verify them separately in the renderer you plan to use.

Not testing opacity behavior: The Ignore invisible objects option can include occluder opacity in the calculation, which may make rendering slower. According to the documentation, in V-Ray GPU this option affects only invisible lights in the scene. Check the result before production in scenes that include transparency or opacity maps.

Using V-Ray Dirt in architectural and archviz workflows

VRayDirt can be useful for architects, interior designers, and visualization artists who want to visually emphasize contact edges, crevices, and the relative positions of objects. You can control the scope of the effect in the scene using the Include/Exclude and Affected by controls. This can make the workflow more manageable in scenes where you don’t want every object to be affected in the same way.

Before applying it, verify three things: a Radius that suits the scene units, support for the required features in the selected renderer, and the settings available in your V-Ray version. The sources do not describe licensing costs or special hardware requirements, so it would not be appropriate to make assumptions about them. In particular, if you use GPU rendering, don’t assume that the result seen on the CPU will be reproduced exactly with every VRayDirt option.

Next steps

In a small section of your scene, first compare the modes, then the Radius, Distribution, and Falloff values. Next, review the Subdivs and Image Sampler Noise threshold settings. Finally, add Bias, Double Sided, or object scope options to determine the result you need. Before moving to a production render, check the settings in the renderer you plan to use and at the actual scale of your scene.

Sources and license

This guide has been adapted into Turkish from the freely licensed Chaos VRayDirt and VRayDirt Nuke documentation. The V-Ray 7 update 5 release notes were also used for version context: VRayDirt documentation, VRayDirt — Nuke documentation, and V-Ray 7 update 5 release notes.