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glgsg: Workaround driver bug causing flickering in AMD RDNA cards

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Apparently, the use of glColorPointer with GL_BGRA causes these cards to display garbled vertex colors (tested with RX 5700 XT).  This bug doesn't seem to affect glVertexAttribPointer.

The "fix" is to just disable packed-dabc colors if these cards are detected.  This may cause a minor performance regression since the vertex data now needs to be munged--possibly even unnecessarily, if shaders are used, but this effect is likely very minor (and can be addressed in other ways).

Fixes #981
This commit is contained in:
rdb 2021-03-25 22:59:35 +01:00
parent 6e0af8abe4
commit c36fa1ef17
3 changed files with 32 additions and 2 deletions
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27
panda/src/glstuff/glGraphicsStateGuardian_src.cxx
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@ -1341,11 +1341,34 @@ reset() {
_supports_packed_dabc = false;
_supports_packed_ufloat = false;
#else
_supports_packed_dabc = is_at_least_gl_version(3, 2) ||
_supports_packed_dabc = (is_at_least_gl_version(3, 2) ||
has_extension("GL_ARB_vertex_array_bgra") ||
has_extension("GL_EXT_vertex_array_bgra");
has_extension("GL_EXT_vertex_array_bgra")) && gl_support_vertex_array_bgra;
_supports_packed_ufloat = is_at_least_gl_version(4, 4) ||
has_extension("GL_ARB_vertex_type_10f_11f_11f_rev");
if (_supports_packed_dabc) {
int number = 0;
if (_gl_renderer.compare(0, 14, "AMD Radeon RX ") == 0) {
number = atoi(_gl_renderer.c_str() + 14);
}
else if (_gl_renderer.compare(0, 10, "Radeon RX ") == 0) {
number = atoi(_gl_renderer.c_str() + 10);
}
// This is buggy for RDNA cards. Verified on 5700 XT, reportedly also
// occurs on the entire 5*00 and 6*00 line.
if (number >= 5000 && number < 8000) {
_supports_packed_dabc = false;
if (GLCAT.is_debug()) {
GLCAT.debug()
<< "Detected AMD Radeon RX " << number
<< ", disabling use of GL_BGRA vertex attributes\n";
}
}
}
#endif
#ifdef OPENGLES

6
panda/src/glstuff/glmisc_src.cxx
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@ -304,6 +304,12 @@ ConfigVariableBool gl_support_shadow_filter
"cards suffered from a broken implementation of the "
"shadow map filtering features."));
ConfigVariableBool gl_support_vertex_array_bgra
("gl-support-vertex-array-bgra", true,
PRC_DESC("Disable this if you suspect a bug in the driver implementation "
"of GL_BGRA vertex arrays. The Radeon RX 5700 XT is an example "
"of a card known to suffer from bugs with this feature."));
ConfigVariableBool gl_force_image_bindings_writeonly
("gl-force-image-bindings-writeonly", false,
PRC_DESC("Forces all image inputs (not textures!) to be bound as writeonly, "

1
panda/src/glstuff/glmisc_src.h
View File

@ -81,6 +81,7 @@ extern ConfigVariableBool gl_fixed_vertex_attrib_locations;
extern ConfigVariableBool gl_support_primitive_restart_index;
extern ConfigVariableBool gl_support_sampler_objects;
extern ConfigVariableBool gl_support_shadow_filter;
extern ConfigVariableBool gl_support_vertex_array_bgra;
extern ConfigVariableBool gl_force_image_bindings_writeonly;
extern ConfigVariableEnum<CoordinateSystem> gl_coordinate_system;