Blender, cycles render. Built for game engine baking on any UV map. The ribs and skull took weeks of experimentation. The ribs still protrude out not quite right in the chest. If I make the ribs look right, then they do not look quite right when exposed by gaping wounds.
But I am done with this shader, it is plenty good enough for most games that are not first person AAA, I think.
This is all procedural. No UV maps, no textures. One material in Blender. The shader is displayed on a the Unity Multipurpose Avatar (UMA) Male model.
This is made with a combination of waves (ribs and Spine), gradients, brick and noise.