I build a rig that allows muscle deformation in real time applications as a part of my thesis in kajak university of applied sciences. I wanted to also wanted to study whether change in the polygon area could be used as mask to apply different texture maps.
The rig works in real time with most game engines and doesn't require additional coding or tools. The rig is also fast to apply to a new character. In the video character has only normal map. In the parts that character has checkered pattern textures, I'm blending 3 texture maps depending on the area increase or decrease of the polygons.
Polygons which area is close to original get yellow texture, polygons that squash get red texture and stretching polygons get green texture. I'm hoping to use these three textures to give the character wrinkles and pronounced muscle features where muscle expansion happens. Some areas work well but some need still work.
Rigging and animation by me. Model by Nick Zuccarello. (http://www.nickzucc.blogspot.com) Downloaded from blendswap.com. the model came with blenrig animation system, blenrig was not used to in this example, this rig was done entirely by me.