On 10/17/2015 07:31 PM, Charmaine Lee wrote:
From: Brian Paul <bri...@vmware.com>
Sent: Friday, October 16, 2015 2:25 PM
To: mesa-dev@lists.freedesktop.org
Cc: Charmaine Lee; Jose Fonseca; Sinclair Yeh
Subject: [PATCH 09/10] vbo: fix GL_LINE_LOOP stray line bug
When long GL_LINE_LOOP primitives don't fit in one vertex buffer they
have to be split across buffers. The code to do this was basically correct
but drivers had to pay special attention to the _mesa_prim::begin,end flags
in order to draw the sections of the line loop properly. Apparently, the
only drivers to do this were those using the old 'tnl' module for software
vertex processing.
Now we convert the split pieces of GL_LINE_LOOP prims into GL_LINE_STRIP
primitives so that drivers don't have to worry about the special begin/end
flags. The only time a driver will get a GL_LINE_LOOP prim is when the
whole thing fits in one vertex buffer.
Most fixes bug 81174, but not completely. There's another bug somewhere
in the src/gallium/auxiliary/draw/ code. If the piglit lineloop test is
run with -count 4096, rendering is correct, but with -count 4097 there are
stray lines. 4096 is a magic number in the draw code (search for "4096").
Also note that this does not fix long line loops in display lists. The
next patch fixes that.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=81174
---
src/mesa/vbo/vbo_context.h | 5 ++++-
src/mesa/vbo/vbo_exec_api.c | 38 +++++++++++++++++++++++++++++++++++++-
src/mesa/vbo/vbo_exec_draw.c | 12 ++++++++++++
3 files changed, 53 insertions(+), 2 deletions(-)
diff --git a/src/mesa/vbo/vbo_context.h b/src/mesa/vbo/vbo_context.h
index 1e85335..28f43b4 100644
--- a/src/mesa/vbo/vbo_context.h
+++ b/src/mesa/vbo/vbo_context.h
@@ -205,7 +205,10 @@ vbo_get_default_vals_as_union(GLenum format)
static inline unsigned
vbo_compute_max_verts(const struct vbo_exec_context *exec)
{
- return (VBO_VERT_BUFFER_SIZE - exec->vtx.buffer_used) /
+ /* Subtract one so we're always sure to have room for an extra
+ * vertex for GL_LINE_LOOP -> GL_LINE_STRIP conversion.
+ */
+ return (VBO_VERT_BUFFER_SIZE - exec->vtx.buffer_used - 1) /
(exec->vtx.vertex_size * sizeof(GLfloat));
Shouldn't this be
(VBO_VERT_BUFFER_SIZE - exec->vtx.buffer_used) / (exec->vtx.vertex_size
*sizeof(GLfloat)) - 1;
Yes, of course. I'll fix that.
-Brian
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