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Fix more polygon winding, culling confusion. 

If the determinant of the triangle is positive, its winding is CCW (right-handed coord system).
This commit is contained in:
Brian 2007-07-13 14:22:46 -06:00
parent 2bf4a500de
commit dc313b5783
3 changed files with 27 additions and 15 deletions
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12
src/mesa/pipe/draw/draw_cull.c
View File

@ -40,7 +40,7 @@
struct cull_stage {
struct draw_stage stage;
GLuint mode; /**< one of PIPE_WINDING_x */
GLuint winding; /**< which winding(s) to cull (one of PIPE_WINDING_x) */
};
@ -54,7 +54,7 @@ static void cull_begin( struct draw_stage *stage )
{
struct cull_stage *cull = cull_stage(stage);
cull->mode = stage->draw->setup.cull_mode;
cull->winding = stage->draw->setup.cull_mode;
stage->next->begin( stage->next );
}
@ -78,10 +78,12 @@ static void cull_tri( struct draw_stage *stage,
header->det = ex * fy - ey * fx;
if (header->det != 0) {
/* non-zero area */
GLuint mode = (header->det > 0) ? PIPE_WINDING_CW : PIPE_WINDING_CCW;
/* if (det > 0 then Z points toward camera and triangle is
* counter-clockwise winding.
*/
GLuint winding = (header->det > 0) ? PIPE_WINDING_CCW : PIPE_WINDING_CW;
if ((mode & cull_stage(stage)->mode) == 0) {
if ((winding & cull_stage(stage)->winding) == 0) {
/* triangle is not culled, pass to next stage */
stage->next->tri( stage->next, header );
}

12
src/mesa/pipe/draw/draw_twoside.c
View File

@ -35,8 +35,7 @@
struct twoside_stage {
struct draw_stage stage;
GLfloat facing;
GLfloat sign; /**< +1 or -1 */
const GLuint *lookup;
};
@ -51,7 +50,12 @@ static void twoside_begin( struct draw_stage *stage )
{
struct twoside_stage *twoside = twoside_stage(stage);
twoside->facing = (stage->draw->setup.front_winding == PIPE_WINDING_CW) ? 1 : -1;
/*
* We'll multiply the primitive's determinant by this sign to determine
* if the triangle is back-facing (negative).
* sign = 1 for CCW, -1 for CW
*/
twoside->sign = (stage->draw->setup.front_winding == PIPE_WINDING_CCW) ? 1 : -1;
stage->next->begin( stage->next );
}
@ -94,7 +98,7 @@ static void twoside_tri( struct draw_stage *stage,
{
struct twoside_stage *twoside = twoside_stage(stage);
if (header->det * twoside->facing < 0) {
if (header->det * twoside->sign < 0.0) {
/* this is a back-facing triangle */
struct prim_header tmp;

18
src/mesa/state_tracker/st_atom_setup.c
View File

@ -78,13 +78,19 @@ static void update_setup_state( struct st_context *st )
/* _NEW_POLYGON, _NEW_BUFFERS
*/
{
setup.front_winding = PIPE_WINDING_CW;
if (ctx->DrawBuffer && ctx->DrawBuffer->Name != 0)
setup.front_winding ^= PIPE_WINDING_BOTH;
if (ctx->Polygon.FrontFace == GL_CCW)
setup.front_winding = PIPE_WINDING_CCW;
else
setup.front_winding = PIPE_WINDING_CW;
if (ctx->Polygon.FrontFace != GL_CCW)
setup.front_winding ^= PIPE_WINDING_BOTH;
/* XXX
* I think the intention here is that user-created framebuffer objects
* use Y=0=TOP layout instead of OpenGL's normal Y=0=bottom layout.
* Flipping Y changes CW to CCW and vice-versa.
* But this is an implementation/driver-specific artifact - remove...
*/
if (ctx->DrawBuffer && ctx->DrawBuffer->Name != 0)
setup.front_winding ^= PIPE_WINDING_BOTH;
}
/* _NEW_LIGHT