Emulator Issues #13733
open
[Graphical emulation issue] CI texture TLUT address calculation is wrong
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Description
Game Name/ID?
Any game
What's the problem? Describe what went wrong.
Current implementation does something like the following (obviously not accurate):
tmem_addr = ( tmem_offset + tex_ci ) & tmem_bank_size_mask;
pixel_color = TMEMGetTlutValue(tmem_addr);
where tmem_offset is the offset of the TLUT begining in high bank TMEM and tex_ci is the current pixel index value of the texture.
As per my testing, the address of a TLUT value should be calculated by using an OR operation:
tmem_addr = ( tmem_offset | tex_ci ) & tmem_bank_size_mask;
Meaning that in real hardware there is no wrapping around high bank TMEM.
Is the issue present in the latest development version?
Yes, Issue occurring as of rev 2412-225
Is the issue present in the latest release?
Yes, as of rev 2409.0
Files
Updated by flacs about 2 months ago
- File tlut_test_hardware_fifoplayer.png tlut_test_hardware_fifoplayer.png added
- Status changed from New to Accepted
Updated by pokechu22 about 1 month ago
I looked at Dolphin's TMEM emulation about a week ago when this was first posted, and I didn't see anything that looked like we implement masking with tmem_bank_size_mask currently either. (I might have just missed it though.)
Updated by Evoca about 1 month ago
pokechu22 wrote in #note-2:
I looked at Dolphin's TMEM emulation about a week ago when this was first posted, and I didn't see anything that looked like we implement masking with
tmem_bank_size_maskcurrently either. (I might have just missed it though.)
Sorry for the inconvenience, I was not really clear with the issue :,)
I used pseudo-code but the functionality is basically the same, for example the DecodeBytes_C8() function (https://github.com/dolphin-emu/dolphin/blob/c770e7c2766155799095d1a1df19f898a2db7bc5/Source/Core/VideoCommon/TextureDecoder_Generic.cpp#L85) receives a pointer to the tlut starting at tlutaddr (see https://github.com/dolphin-emu/dolphin/blob/c770e7c2766155799095d1a1df19f898a2db7bc5/Source/Core/VideoCommon/TextureInfo.cpp#L33C1-L33C68) and it has access to all the 256 TLUT values starting from there.
In real hardware the tlutaddr and the index value (val in DecodeBytes_C8()) are ORed together (meaning set bits from tlutaddr make certain TLUT values unreachable). As for real modifications (at least from what I see in the code above), the whole high tmem should be passed and val should be ORed with tlutaddr before accessing the tlut.