Quick Tip: How to Make Easy Grunge in Blender

Written by Laurent Marechal - 17 july 2015

Classified in : Blender, Links - Tags : Blender, Cycle

Site d'origine : http://www.blenderguru.com/tutorials/how-to-grunge/

Adding grunge in Blender is loads of fun, we just need to make a clean version of the material and a dirty one, and then use a custom mask to mix those together.

Clean and dirty materials that will be mixed together

Now to add the dirt into only the corners, we can either paint a mask by hand, or bake an Ambient Occlusion (AO) map.

If you want exact control over which corners and crevices are dirty, painting the mask by hand would be your best option. But if you’re not particularly fussed, AO is a nice cheap solution.

In this case, I simply baked the AO:

If you’d like to know exactly how to bake the AO, check out the video above, or Andrew’s Introduction to Baking in Cycles.

The key thing here is that the darker an area is, the more dirty it will appear.

Then the trick is to add a bit of texture to the dirt map by overlaying a very contrasty texture (I used this one):

The blue node is the AO map that we baked, which is put though a ColorRamp to give it more contrast. The brown node is a grunge texture that really gives some nice detail to our dirtmap when we mix is with the AO using the Overlay blending mode.

Here’s what that looks like: