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Inside a modifier volume the PowerVR2 scales what a polygon is shaded with, its base and offset colours, and then combines them with the texture and fogs the result as usual. The OpenGL and Vulkan per-triangle renderers darkened the finished pixel instead, with one quad over the screen. That is the same thing for a modulated texture and nothing else: it also darkened a decal texture, which the hardware leaves alone, and the fog on top. They now do what the per-pixel renderers do, by drawing twice. Once the volumes are in the stencil buffer, the opaque and punch-through polygons that take shadows are drawn again with a shader variant that scales the two colours (pp_Shadowed), into the pixels that are theirs (depth equal) and in a volume (stencil). What that costs is kept to where the shadows are. The rectangle of the screen the pass's volumes cover is taken from their vertices; only polygons that reach into it are drawn again, and only the part of them inside it, by scissor. Nothing outside that rectangle can be in a volume, so this leaves out no pixel that would have changed. A frame without modifier volumes does nothing new, and the shaders of polygons drawn the first time are the same as before. The darkening quad stays, for what cannot be drawn twice: polygons that are blended, and opaque ones that wrote no depth to be found by. The pixels drawn again are marked in stencil bit 6 and the quad skips them; anything not marked is darkened as it was. Where two polygons are at the very same depth, the mark is also what keeps the one that was left showing the first time as the one left showing now. Within a frame of several render passes only the pass's own polygons are drawn again. Bump-mapped polygons have their offset values scaled like any others, as in the per-pixel renderers. rend/shadows.h holds what the two renderers share. tools/pvr's OpenGL ES 2 test compiles the shadowed variants on an OpenGL ES 2 context and checks that white comes out grey without a texture and green with a green decal texture.