This is something I've been aware of for quite a while.. Some triangles can show "patchiness" on the inside. The tyres are a good example of this. My question is, is it just an alpha issue (which I hear, is tricky for GPUs to render), or is it a problem? Maybe it's sometimes an issue? I don't know, I normally check all the faces are the right way, and then ignore it, but should I? Here's some examples:
to me it looks like a bad triangle sorting using lequal ztest and zwrite on and additive blending operator in the transparent render pass, nothing to worry about, is a game render issue what that means and does for dummies: it calculates the pixels for each triangle, and for each pixel, if the calculated depth (in the depth buffer) is closer to viewport than current value on screen, it adds the color*alpha to the screen, and writes the Z to depth buffer if it happens to draw the closer triangles first, the ones behind wont add anything, as the calculated depth wont be closer to current anymore (darker ones) if it happens to draw the farther triangles first, the ones in front will later add color+alpha again in some pixels (causing lighter ones) usually for transparent passes you sort the triangles in a front-to-back way but that might be too expensive for rendering a "triangle debugging" feature so they mostly skipped it intentionally
