Texture Extraction - Luminosity Key

Working on VFX in the gaming industry requires the skill to extract interesting parts of textures from assets like photos. So here I’m using a luminosity key to do exactly that. This isn’t rendered through the engine but it’s the same concept.

 

Read on for a break down of how I do it

I somehow lost the original asset for the above picture but I’ll demonstrate the process below with a new texture.
 

 

The idea is to get an image with interesting patterns in it which would suit your needs and then extract that from the image.
The concept of the luminosity mask is that it will highlight the lighter areas, of that with more luminosity, and then create a mask from that. So for example in the picture below we want the white foam as this has some interesting patterns in it for fantasy like effects, But we have a problem, we want to extract only that, and not the other elements. So we need to make sure we get a clean mask, the outcome of the mask is very subjective.  The way of getting this clean mask is simple, create a great deal of contrast in the image. Depending if you want a solid alpha mask of you want some gray scale in image will dictate how much contrast you put into the image.
Below is a quick over view of what image represents
1.    Original Photo
2.    Make Black and White
3.    Create a high contrast
4.    Invert to check
5.    Create more contrast with Gamma correction in the exposure tool
6.    Luminosity mask (Ctrl+Alt+2)
7.    Tilled Images
8.    Alpha