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[cogl journal] If we are only flushing one quad use a TRIANGLE_FAN

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At the moment Cogl doesn't do much batching of quads so most of the time we
are flushing a single quad at a time.  This patch simplifies how we submit
those quads to OpenGL by using glDrawArrays with GL_TRIANGLE_FAN mode
instead of sending indexed vertices using GL_TRIANGLES mode.

Note: I hope to follow up soon with changes that improve our batching and
also move the indices into a VBO so they don't need to be re-validated every
time we call glDrawElements.
This commit is contained in:
Robert Bragg 2009-05-28 02:03:16 +01:00
parent 4b105deb35
commit 43623a6c44
1 changed files with 46 additions and 34 deletions
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80
common/cogl-primitives.c
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@ -72,35 +72,6 @@ _cogl_journal_flush_quad_batch (CoglJournalEntry *batch_start,
_COGL_GET_CONTEXT (ctx, NO_RETVAL);
/* The indices are always the same sequence regardless of the vertices so we
* only need to change it if there are more vertices than ever before. */
needed_indices = batch_len * 6;
if (needed_indices > ctx->static_indices->len)
{
int old_len = ctx->static_indices->len;
int vert_num = old_len / 6 * 4;
GLushort *q;
/* Add two triangles for each quad to the list of
indices. That makes six new indices but two of the
vertices in the triangles are shared. */
g_array_set_size (ctx->static_indices, needed_indices);
q = &g_array_index (ctx->static_indices, GLushort, old_len);
for (i = old_len;
i < ctx->static_indices->len;
i += 6, vert_num += 4)
{
*(q++) = vert_num + 0;
*(q++) = vert_num + 1;
*(q++) = vert_num + 3;
*(q++) = vert_num + 1;
*(q++) = vert_num + 2;
*(q++) = vert_num + 3;
}
}
/* XXX NB:
* Our vertex data is arranged as follows:
* 4 vertices per quad: 2 GLfloats per position,
@ -150,11 +121,52 @@ _cogl_journal_flush_quad_batch (CoglJournalEntry *batch_start,
GE (glVertexPointer (2, GL_FLOAT, stride, vertex_pointer));
_cogl_current_matrix_state_flush ();
GE (glDrawRangeElements (GL_TRIANGLES,
0, ctx->static_indices->len - 1,
6 * batch_len,
GL_UNSIGNED_SHORT,
ctx->static_indices->data));
if (batch_len > 1)
{
/* The indices are always the same sequence regardless of the vertices so
* we only need to change it if there are more vertices than ever before.
*/
needed_indices = batch_len * 6;
if (needed_indices > ctx->static_indices->len)
{
int old_len = ctx->static_indices->len;
int vert_num = old_len / 6 * 4;
GLushort *q;
/* Add two triangles for each quad to the list of
indices. That makes six new indices but two of the
vertices in the triangles are shared. */
g_array_set_size (ctx->static_indices, needed_indices);
q = &g_array_index (ctx->static_indices, GLushort, old_len);
for (i = old_len;
i < ctx->static_indices->len;
i += 6, vert_num += 4)
{
*(q++) = vert_num + 0;
*(q++) = vert_num + 1;
*(q++) = vert_num + 3;
*(q++) = vert_num + 1;
*(q++) = vert_num + 2;
*(q++) = vert_num + 3;
}
}
GE (glDrawRangeElements (GL_TRIANGLES,
0, ctx->static_indices->len - 1,
6 * batch_len,
GL_UNSIGNED_SHORT,
ctx->static_indices->data));
}
else
{
GE (glDrawArrays (GL_TRIANGLE_FAN,
0, /* first */
4)); /* n vertices */
}
/* DEBUGGING CODE XXX: