How to use RichDirt + mental ray + 3ds Max RTT

(Scroll down for V-Ray version) Render To Texture (RTT) is used a lot to bake information for game engines, or to an object during animation. RTT can be used to create a pure dirt texture, or a texture that contains diffuse, dirt and global illumination. The later is -easier- in 1 sentence - apply RichDirt to the diffuse channel of your materials and then do the baking like you always did. If you want to have dirt isolated, do the steps described below:

  1. Select mental ray as renderer. Rendering -> Render Setup -> Common tab -> scroll down to ´Assign Renderer´ -> select mental ray
  2. Rendering -> Render Setup dialog -> choose the Processing tab. Enable ´Material Override´ and create a ´mental ray´ material here.
  3. Drag the new material to the material editor
  4. Assign RichDirt to the ´surface´ slot (see image below).
  5. Start RTT (Rendering -> Render To Texture )
  6. Select the -DiffuseMap- as Element.
  7. Render (do the usual RTT steps like you would do without RichDirt, like adding an image name, selecting an object to RTT).

Why to use the ´mental ray material´s surface slot ? We don´t want lights and shadows applied. By directly adding the RichDirt texture to the ´surface´ slot one can skip lighting and shadows.

Is it possible to use a ´regular´ material as well ? Is it required to use the ´Material Override´ (step 2 and 3 above) ? No ! You can use any material, add a ´mental ray´ material and RichDirt in the surface slot. Using the ´Material Override´ allows to quickly add dirt to more objects in the scene. Using ´regular´ materials is more work, but it also is more flexible, like having different dirt for every object. Choose what works best for your workflow.

Increase your efficiency: You can create several materials and save to a lib to easily throw them at different objects to weather buildings or make objects dirty.

RTT on a simple cube, using streaks and splashes

Select a "mr material"
RichDirt assigned to "surface" slot.

How to use V-Ray+ RichDirt + 3ds Max RTT

A really excellent tutorial on RTT with V-Ray is found here. This tutorial is for V-Ray 1.5, so the global illumination settings are a bit different in 2.x and 3.x , but the Render-To-Texture part works directly with the newer version of V-Ray. Adding RichDirt is very easy. Simply go to the material, and plug it into the diffuse slot. The image below shows the spot3d model enhanced with a RichDirt texture. A brown color is used to create a rust-like effect.

The material uses RichDirt with a radius of 30 cm, and a Falloff of 20. Up slope is active as well although it isn´t stritcly required to get a nice result. Using VrayCompleteMap RichDirt is baked to the texture, as seen in the image below:

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