The Tantalus games (Cars Race-O-Rama, MX vs ATV Reflex and Untamed, SpongeBob)
turn depth into fog with a CLUT16 read of the swizzled depth mirror, stretched
2x into a 565 view of an 8888 buffer. A following 8888 copy writes the scene's
RGB and keeps the alpha, so each pixel's fog factor is the upper 565 half.
At a higher render scale, the depth X swizzle snapped every render pixel to its
PSP pixel's left edge, so the fog came out in PSP-pixel blocks. It now keeps the
position within the PSP pixel. That leaves the upper half sampling the right
half of the depth texel, half a pixel off the scene, which drew magenta halos on
the right of objects in Cars. With the new DepthCLUTIntoHalves compat flag, the
depal pass outputs twice as wide so each render pixel reads its own 8888 pixel's
depth.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Note that we also offset the lookup slightly to miss the wrap-around
points. The existing 31 scale factor instead of 32, together with that
half-texel, are enough to avoid that problem.
Fixes#18300
