From fe2f5cfdc7439cbe481d4bea393b46395967a8a3 Mon Sep 17 00:00:00 2001 From: Brian Paul Date: Fri, 18 Aug 2017 21:03:16 -0600 Subject: [PATCH] vbo: fix glVertexAttrib(index=0) MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Charmaine Lee --- src/mesa/vbo/vbo_attrib_tmp.h | 7 +++++-- src/mesa/vbo/vbo_exec_array.c | 2 +- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/src/mesa/vbo/vbo_attrib_tmp.h b/src/mesa/vbo/vbo_attrib_tmp.h index 5718ac5a092..126e4ef0d6e 100644 --- a/src/mesa/vbo/vbo_attrib_tmp.h +++ b/src/mesa/vbo/vbo_attrib_tmp.h @@ -524,15 +524,18 @@ TAG(MultiTexCoord4fv)(GLenum target, const GLfloat * v) /** * If index=0, does glVertexAttrib*() alias glVertex() to emit a vertex? + * It depends on a few things, including whether we're inside or outside + * of glBegin/glEnd. */ static inline bool is_vertex_position(const struct gl_context *ctx, GLuint index) { - return index == 0 && _mesa_attr_zero_aliases_vertex(ctx); + return (index == 0 && + _mesa_attr_zero_aliases_vertex(ctx) && + _mesa_inside_begin_end(ctx)); } - static void GLAPIENTRY TAG(VertexAttrib1fARB)(GLuint index, GLfloat x) { diff --git a/src/mesa/vbo/vbo_exec_array.c b/src/mesa/vbo/vbo_exec_array.c index edd55ce69e2..e3421fa9b51 100644 --- a/src/mesa/vbo/vbo_exec_array.c +++ b/src/mesa/vbo/vbo_exec_array.c @@ -356,7 +356,7 @@ recalculate_input_bindings(struct gl_context *ctx) else if (array[VERT_ATTRIB_POS].Enabled) inputs[0] = &vertexAttrib[VERT_ATTRIB_POS]; else { - inputs[0] = &vbo->currval[VBO_ATTRIB_POS]; + inputs[0] = &vbo->currval[VBO_ATTRIB_GENERIC0]; const_inputs |= VERT_BIT_POS; } -- 2.30.2