[spicyjpeg]

There actually is a relatively simple, if hacky, way to accomplish this: the emulated GTE can push the Z coordinate (and optionally the full-precision X/Y coordinates) of each processed vertex into a private key-value store, using the rounded X/Y result returned to the game as a key. The emulated GPU can then look up the coordinates provided by the game - assuming they were passed as-is from the GTE, which is the case for the vast majority of games - in the same store to obtain the Z values.

This does not seem to be a new approach, as PC ports of PS1 games used similar tricks all the way back in 2000 [1].

[1] https://news.ycombinator.com/item?id=3581350 https://news.ycombinator.com/item?id=29493242