[Mesa-dev] [PATCH 09/10] vbo: fix GL_LINE_LOOP stray line bug
Brian Paul
brianp at vmware.com
Sat Oct 17 09:13:05 PDT 2015
On 10/17/2015 06:20 AM, Roland Scheidegger wrote:
> FWIW this probably fixes
> https://bugs.freedesktop.org/show_bug.cgi?id=49779 and
> https://bugs.freedesktop.org/show_bug.cgi?id=28130 (in contrast to 81174
> which as you noted suffers both from a vbo and draw issue). (I believe
> the issue in draw is pretty much the same, since things are split with
> too large buffers we end up with multiple (incorrect) line loops.)
I'm going to close those as dups of 81174. 49779 also mentions
llvmpipe. They're surely all the same issue.
-Brian
>
> Roland
>
>
> Am 16.10.2015 um 23:25 schrieb Brian Paul:
>> 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://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D81174&d=BQIGaQ&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=Vjtt0vs_iqoI31UfJxBl7yv9I2FeiaeAYgMTLKRBc_I&m=czG7W6Vef1aFb_D_GLNGA4H62ZBA3g5g8aoKQ6VxP98&s=Cu81rzD4sulAjES4I4QraL70LU5mqxScNcy3-9wGvqc&e=
>> ---
>> 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));
>> }
>>
>> diff --git a/src/mesa/vbo/vbo_exec_api.c b/src/mesa/vbo/vbo_exec_api.c
>> index 0116f56..3c25ec0 100644
>> --- a/src/mesa/vbo/vbo_exec_api.c
>> +++ b/src/mesa/vbo/vbo_exec_api.c
>> @@ -61,7 +61,8 @@ static void reset_attrfv( struct vbo_exec_context *exec );
>>
>> /**
>> * Close off the last primitive, execute the buffer, restart the
>> - * primitive.
>> + * primitive. This is called when we fill a vertex buffer before
>> + * hitting glEnd.
>> */
>> static void vbo_exec_wrap_buffers( struct vbo_exec_context *exec )
>> {
>> @@ -83,6 +84,22 @@ static void vbo_exec_wrap_buffers( struct vbo_exec_context *exec )
>>
>> last_count = last_prim->count;
>>
>> + /* Special handling for wrapping GL_LINE_LOOP */
>> + if (last_prim->mode == GL_LINE_LOOP &&
>> + last_count > 0 &&
>> + !last_prim->end) {
>> + /* draw this section of the incomplete line loop as a line strip */
>> + last_prim->mode = GL_LINE_STRIP;
>> + if (!last_prim->begin) {
>> + /* This is not the first section of the line loop, so don't
>> + * draw the 0th vertex. We're saving it until we draw the
>> + * very last section of the loop.
>> + */
>> + last_prim->start++;
>> + last_prim->count--;
>> + }
>> + }
>> +
>> /* Execute the buffer and save copied vertices.
>> */
>> if (exec->vtx.vert_count)
>> @@ -98,6 +115,7 @@ static void vbo_exec_wrap_buffers( struct vbo_exec_context *exec )
>>
>> if (_mesa_inside_begin_end(exec->ctx)) {
>> exec->vtx.prim[0].mode = exec->ctx->Driver.CurrentExecPrimitive;
>> + exec->vtx.prim[0].begin = 0;
>> exec->vtx.prim[0].start = 0;
>> exec->vtx.prim[0].count = 0;
>> exec->vtx.prim_count++;
>> @@ -827,6 +845,24 @@ static void GLAPIENTRY vbo_exec_End( void )
>> last_prim->end = 1;
>> last_prim->count = exec->vtx.vert_count - last_prim->start;
>>
>> + /* Special handling for GL_LINE_LOOP */
>> + if (last_prim->mode == GL_LINE_LOOP && last_prim->begin == 0) {
>> + /* We're finishing drawing a line loop. Append 0th vertex onto
>> + * end of vertex buffer so we can draw it as a line strip.
>> + */
>> + const fi_type *src = exec->vtx.buffer_map;
>> + fi_type *dst = exec->vtx.buffer_map +
>> + exec->vtx.vert_count * exec->vtx.vertex_size;
>> +
>> + /* copy 0th vertex to end of buffer */
>> + memcpy(dst, src, exec->vtx.vertex_size * sizeof(fi_type));
>> +
>> + assert(last_prim->start == 0);
>> + last_prim->start++; /* skip vertex0 */
>> + /* note that last_prim->count stays unchanged */
>> + last_prim->mode = GL_LINE_STRIP;
>> + }
>> +
>> try_vbo_merge(exec);
>> }
>>
>> diff --git a/src/mesa/vbo/vbo_exec_draw.c b/src/mesa/vbo/vbo_exec_draw.c
>> index 397fc09..f91f7c8 100644
>> --- a/src/mesa/vbo/vbo_exec_draw.c
>> +++ b/src/mesa/vbo/vbo_exec_draw.c
>> @@ -110,6 +110,18 @@ vbo_copy_vertices( struct vbo_exec_context *exec )
>> return 1;
>> }
>> case GL_LINE_LOOP:
>> + if (last_prim->begin == 0) {
>> + /* We're dealing with the second or later section of a split/wrapped
>> + * GL_LINE_LOOP. Since we're converting line loops to line strips,
>> + * we've already increment the last_prim->start counter by one to
>> + * skip the 0th vertex in the loop. We need to undo that (effectively
>> + * subtract one from last_prim->start) so that we copy the 0th vertex
>> + * to the next vertex buffer.
>> + */
>> + assert(last_prim->start > 0);
>> + src -= exec->vtx.vertex_size;
>> + }
>> + /* fall-through */
>> case GL_TRIANGLE_FAN:
>> case GL_POLYGON:
>> if (nr == 0) {
>>
>
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