3D tutorial
UV-Map Dirtmap Baker tutorial for Cinema 4D

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The "UV-Map Dirtmap Baker" Tutorial

Cinema 4D veteran Peter Hofmann aka peXel presents us with this handy tutorial covering the following topics:

How to get a "clean" UV - Map?

How to calculate a Dirt - Map?

How to work with Baker?

Software requirements: CINEMA 4D R8.5 ..., BODYPAINT 2

Introduction.

As we cannot use the Dirt shader for animations, you have to generate a Dirt map. For the Dirt map calculation you have to unwrap and unfold the UV mesh of your object first. As this can be a very time consuming process in BODYPAINT 3D, you should avoid high resolution meshes. Try to use a combination of low polygon objects with HyperNURBS objects.

How to get a "clean" UV - Map

Don't get confused if you read about UV maps and UVW maps. Both are the same, but you can only generate and edit the UV part of the UVW map. The "W" coordinate stands for the distance between the texture and the surface which is only relevant for volume shaders. BODYPAINT 3D only displays and generates the UV part of the data.

The functions used are:

UV Terrace
Relax UV
Mapping: Realign

These three functions are all you need! At first you should use the Paint Setup Wizard to unwrap your mesh in a way we could work with it. It gives you two UV options to choose from: The Optimal Cubic - or the Optimal Angle- Mode. In my example it's better to use the Optimal Angle - Mode. All 3D elements are transferred to individual 2D coordinates.

Applying the functions.

Now we can enhance this map with Mapping: Realign. After that you can use Relax UV with activated Fix Border option. Now it looks much better and more relaxed : All overlaps are gone!
Unfortunately it is still looking more like a puzzle, but you can realign the UV polygons with the UV Terrace function. You have to select one of the polygons and use the UV Terrace function. You will see the parts to which that polygon is corresponding in the Texture window. Most of the time you'll have to undo the tool again and connect surrounding polygons manually. Repeat these steps until all corresponding parts are found. It's better to fill the empty polygon holes first! This prevents the UV map from becoming too chaotic.

Positioning the parts.

If all parts are selected, scale them down and bring them into their final position. You can use UV Terrace afterwards to fit all parts into your 2D - Map. Don't forget to use the Relax UV function from time to time.
The final result should be something like this:

Dirt - Map ! No idea, how to do that ? :)

We need a very smooth UV - Map for this. After the previous steps we have a good UV - Map for a low resolution mesh. Converting it to a high resolution UV - Map is easy: First save your new UV - Map. Now open a new file and reload the mesh with that new UV - Map. Group your low resolution object under a HyperNURBS object with 2/2 (Edge -Mode R8.5 …) subdivisions and convert it. Now we have a smooth UV Map. So we can start with the Dirt - Map calculation (Render -> calculate dirt …). Do not forget to merge all other surrounding objects to this scene again before starting the Dirt calculation, as those objects will be "seen" by the Dirt map calculation.

Now you have a Dirt - Map, but the most difficult part is still to come. A small hint: In the Alpha channel you need to activate the Soft option, because you want to animate that object. On the other hand the Soft mode has the disadvantage of not giving precise results. We can solve this problem with a Gradient, in our case the Colorizer shader. As our Dirt material is a little bit too washed out, we use the Fusion shader with the Colorizer and a Noise (use overlay). Do not use Random, "Poxl" and "Stupl". These are not very useful for animations as you have to bake them first. More about this a little bit later. For the Colorizer you can use setting like these:

Don't forget to activate the Invert option in your materials Alpha channel ! Above is The resultating Dirt - Map. You can now correct your UV Map in Bodypaint, if necessary.
How to use Baker ?
Here are some of the needed settings to make Baker work:
Auto light = Off (no active lights in your scene file!!
Environment object = 100 %
Baker: Pixelbuffer > 1

I hope this small tutorial gives a little inspiration how to use Dirt maps and Baker.
Best regards
Peter Hofmann "peXel"
Special thanks to Arndt von Koenigsmarck