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authorBrian Paul <[email protected]>2017-08-18 21:03:16 -0600
committerBrian Paul <[email protected]>2017-08-24 07:36:10 -0600
commitfe2f5cfdc7439cbe481d4bea393b46395967a8a3 (patch)
tree1adb3ea286488795c95a861d10ca8d67a21b1d27 /src/mesa/vbo/vbo_exec.h
parenta7e65a443f8aebd40b573a1e16375193c21c36cc (diff)
vbo: fix glVertexAttrib(index=0)
Depending on which extension or GL spec you read the behavior of glVertexAttrib(index=0) either sets the current value for generic attribute 0, or it emits a vertex just like glVertex(). I believe it should do either, depending on context (see below). The piglit gl-2.0-vertex-const-attr test declares two vertex attributes: attribute vec2 vertex; attribute vec4 attr; and the GLSL linker assigns "vertex" to location 0 and "attr" to location 1. The test passes. But if the declarations were reversed such that "attr" was location 0 and "vertex" was location 1, the test would fail to draw properly. The problem is the call to glVertexAttrib(index=0) to set attr's value was interpreted as glVertex() and did not set generic attribute[0]'s value. Interesting, calling glVertex() outside glBegin/End (which is effectively what the piglit test does) does not generate a GL error. I believe the behavior of glVertexAttrib(index=0) should depend on whether it's called inside or outside of glBegin/glEnd(). If inside glBegin/End(), it should act like glVertex(). Else, it should behave like glVertexAttrib(index > 0). This seems to be what NVIDIA does. This patch makes two changes: 1. Check if we're inside glBegin/End for glVertexAttrib() 2. Fix the vertex array binding for recalculate_input_bindings(). As it was, we were using &vbo->currval[VBO_ATTRIB_POS], but that's interpreted as a zero-stride attribute and doesn't make sense for array drawing. No Piglit regressions. Fixes updated gl-2.0-vertex-const-attr test and passes new gl-2.0-vertex-attrib-0 test. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101941 Reviewed-by: Marek Olšák <[email protected]> Reviewed-by: Charmaine Lee <[email protected]>
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