False Color Textures
By Neil Blevins
June 12th 2014

Here's one of the painted texture maps for the main robot in my project "Inc".



Your first question might be "what the heck is this, doesn't look like any texture map I've seen". This texture map is a series of 3 greyscale masks, one mask per channel RGB, and will be used to blend between a metal, paint and rust material. This technique is called False Color Textures, because the texture isn't meant to look like the final thing on your model (like a color map), instead its 3 different values put into a single bitmap, but meant to be split apart once you bring the texturemap into your 3d program.

This funky colored image is really just 3 separate greyscale bitmaps:



These sorts of images can be either painted as 3 separate greyscale maps in photoshop and then combined, or in my case, I just paint on 3 different layers using only the color red, blue or green, and then set all 3 layers to Additive layer mode to create the final image.

Now let me explain how I'm using these 3 channels in my material in my 3d app:
  1. First the model gets a metal material.
  2. Then on top is layered a paint material that contains procedural paint chipping, see my lesson Worn Edges Using A Distorted Vertex Map for details.
  3. Then the red channel of this texture map adds some paint back in places to cover over the procedural
  4. Then the green channel removes larger chunks of paint, revealing the metal below
  5. Then the blue channel blends a rust over top of the metal and paint.
Why use a single false color image instead of 3 greyscale maps? Two reasons...
  1. You now only have a single bitmap to deal with instead of 3. Means far less clutter in your maps directory, especially if your model has a lot of bitmaps, and more difficult to accidentally misplace related bitmaps.
  2. Some renderers internally convert all greyscale bitmaps into rgb, which wastes bitmap memory. So this technique can save memory in some instances. (1 rgb map instead of 3 in memory).
There are a number of ways to extract the channels from your bitmap to be used in your material
  1. Use Cuneyt's ColorCorrect plugin (in the RGBA Space Channels Mapping area)
  2. Use max's built in ColorCorrection node (in the Channels Dropdown)
  3. Use RGB Tint, just make the desired channel white and the others black (thanks to Mitch Gates for the tip)
Anyways, just another tool, something to consider when you have a bunch of related greyscale maps.


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