https://bugs.freedesktop.org/show_bug.cgi?id=70327
Priority: medium Bug ID: 70327 Assignee: dri-devel@lists.freedesktop.org Summary: Casting floating point variable to integer not working properly while constant gets converted properly Severity: normal Classification: Unclassified OS: Linux (All) Reporter: tony.wasserka@dolphin-emu.org Hardware: All Status: NEW Version: git Component: Drivers/Gallium/r600 Product: Mesa
Created attachment 87353 --> https://bugs.freedesktop.org/attachment.cgi?id=87353&action=edit Full rendered scene with bug visible
I've recently been working on converting the shaders used by the Dolphin emulator to use integers instead of floating point numbers (for better emulation accuracy). This seems to have exposed a bug in the r600g driver possibly related to float->int casting.
The core of the issue is this GLSL code line: "iprev.rgb = (iprev.rgb * (int(256.0-fog))) / 256;" (*)
where fog has been initialized before as "float fog = clamp(ze - fog_uniform.z, 0.0, 1.0);"
The point is, while "fog" seems to be zero (a "fog==0.0" condition in the code will return true), the pixel shader result of (*) is different than the one that I get by substituting "fog" with 0.0. This gets very apparent in the rendered scene, cf