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paint-volume: Fix culling bug to handle partial culls

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This updates the inner loops of the cull function so now the vertices of
the polygon being culled are iterated in the inner loop instead of the
clip planes and we count how many vertices are outside the current
plane so we can bail out immediately if all the vertices are outside of
any plane and so we can correctly track partial intersections with the
clip region.

The previous approach could catch some partial intersections but for
example a rectangle that was larger than the clip region centred over
the clip region with all corners outside would be reported as outside,
not as a partial intersection.
This commit is contained in:
Robert Bragg 2011-03-15 10:23:41 +00:00
parent 151b80a837
commit 114133c98c
1 changed files with 16 additions and 22 deletions
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38
clutter/clutter-paint-volume.c
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@ -922,8 +922,7 @@ _clutter_paint_volume_cull (ClutterPaintVolume *pv,
{
int vertex_count;
ClutterVertex *vertices = pv->vertices;
gboolean in = TRUE;
gboolean out = TRUE;
gboolean partial = FALSE;
int i;
int j;
@ -942,10 +941,10 @@ _clutter_paint_volume_cull (ClutterPaintVolume *pv,
else
vertex_count = 8;
for (i = 0; i < vertex_count; i++)
for (i = 0; i < 4; i++)
{
gboolean point_in = TRUE;
for (j = 0; j < 4; j++)
int out = 0;
for (j = 0; j < vertex_count; j++)
{
ClutterVertex p;
float distance;
@ -953,32 +952,27 @@ _clutter_paint_volume_cull (ClutterPaintVolume *pv,
/* XXX: for perspective projections this can be optimized
* out because all the planes should pass through the origin
* so (0,0,0) is a valid v0. */
p.x = vertices[i].x - planes[j].v0.x;
p.y = vertices[i].y - planes[j].v0.y;
p.z = vertices[i].z - planes[j].v0.z;
p.x = vertices[j].x - planes[i].v0.x;
p.y = vertices[j].y - planes[i].v0.y;
p.z = vertices[j].z - planes[i].v0.z;
distance =
planes[j].n.x * p.x + planes[j].n.y * p.y + planes[j].n.z * p.z;
planes[i].n.x * p.x + planes[i].n.y * p.y + planes[i].n.z * p.z;
if (distance < 0)
{
point_in = FALSE;
break;
}
out++;
}
if (!point_in)
in = FALSE;
else
out = FALSE;
if (out == 4)
return CLUTTER_CULL_RESULT_OUT;
else if (out != 0)
partial = TRUE;
}
if (in)
return CLUTTER_CULL_RESULT_IN;
else if (out)
return CLUTTER_CULL_RESULT_OUT;
else
if (partial)
return CLUTTER_CULL_RESULT_PARTIAL;
else
return CLUTTER_CULL_RESULT_IN;
}
void