i was just googling aswell and snooping around in renderdoc (i’m totally new to that one and it does not give me stepped visual representation i need to understand this). apparently ue4.x has a material switch to compute opacity in the early z-pass. i reckon this would update the depth buffer.
in theory you draw whatever anyway. if a pixel is alpha masked aka empty it would write it’s depth and flag like a stencil bit and continue to draw polygons. if the next one is in front it will simply overwrite depth to be more in front. if it’s in the back it will check the bit and it will update to it’s own depth if it’s 0.
the depth write will always occur if a change is happening. front or back. so… the depth pass will have the same overdraw. for sure will not execute the whole surface shader.