When the inverted depth range is unsupported and zRange is greater than farZ then min_depth becomes a negative value and far_depth will then exceed a depth of 1.0 (which is outside the scope of most backends and greater than GX_MAX_DEPTH of the console).
This happens when the backend supports depth clamping the min_depth is not clamped to zero.
This normalization was added in 02ac5e95c8, and changed to use floats in 4bf031c064. The conversion to floats means that sometimes there is insufficient precision for the normalization process, which results in values of NaN or infinity. Performing the whole process with doubles prevents that, but games also sometimes set the values to NaN or infinity directly (possibly accidentally due to the values not being initialized due to them not being used in the current configuration?).
The version of Mesa currently in use on FifoCI (20.3.5) has issues with NaN. Although this bug has been fixed (https://gitlab.freedesktop.org/mesa/mesa/-/commit/b3f3287eac066eae16dce0e47aad3229dcff8257 in 21.2.0), FifoCI is stuck with the older version.
This change may or may not be incorrect, but it should result in the same behavior as already present in Dolphin, while working around the Mesa bug.
CrossVR
Jordan Woyak
iwubcode
Patrick Ferry
Robin Kertels
Scott Mansell
TellowKrinkle
Admiral H. Curtiss
Pokechu22
Dentomologist