Emulator

As everyone knows, F-Zero GX's (GFZE01) shadows show up scrambled when EFB to Texture is used, and can be fixed by turning on EFB to Ram (issue 5122). However the shadows can work in EFB to Texture. In fact, it can be perfectly controlled and is highly reproducible.

With EFB to Texture running, test it in practice mode. Pick any car, set it to 29 AIs, and go to any track. At the start of the race, all cars will have working shadows. Whenever a racer gets far enough off-screen that their shadow is culled by LOD, their shadow will glitch. So throughout the race, more and more shadows of AI cars will become glitched. The same rules apply to your car as well. If your shadow is off screen it will glitch out, either from running off the track (and get recovered) or if you stay in the first person view long enough (5-10) seconds.

Here's a video demonstrating how easy it is to do - http://www.youtube.com/watch?feature=player_detailpage&v=W7xhE1WiY_k

We don't know why the grand prix never has working shadows with EFB to Tex, but we have a theory. In practice mode, there is a small pause immediately before the race starts, presumably loading. In the Grand Prix, the loading pause is way earlier, as soon as you select a cup. Apparently the game loads as soon as it knows what track is selected. With Grand Prix, it's very early in the process. With Practice Mode, it's dead last, after car select and just before the race. Our guess is that Grand Prix is delayed enough that it causes the shadows cache or whatever to reset, or displaying the cars in the car select resets it.

Now, obviously, EFB to Ram fixes the shadow problem in all cases, and it has little impact on performance for this game. This isn't about trying to get more performance or anything. There is something wrong with EFB to Texture, and with this information this bug is a lot easier to understand and hopefully easier to fix. Fixing it here could fix other games, as well as put yet another game on the "awesome works by default" list.

Tested on 3.0 x64, 3.5-420 x64, 3.5-421 x64, and 3.5-426 x64. This is a long standing and well known issue, so didn't see the need to do tons of various revision testing. Everyone knows this has existed forever.

Tested by MaJoR and JMC4789 and reproduced by both, on two computers:

Core i5 3570K @ 4.7ghz
nVidia GTX275
Windows 7 x64

Core i5 720 @ 3.8ghz
nVidia GTX470
Windows 7 x64

Fifo player causes the glitch, Fifo logs cannot be used.