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Avoid bias when calculating quad split direction 

Some error checks weren't being done in both directions
when calculating the best split direction for a quad.
This commit is contained in:
Campbell Barton 2017-09-19 15:03:58 +10:00
parent 9a2f7dd77b
commit 36f5972ed0
Notes: blender-bot 2023-02-14 08:47:25 +01:00 
Referenced by issue #53683, 2.79a release
Referenced by issue #52825, Bmesh - Incorrect boolean with vertex in in triangle exactly intersecting a face
Referenced by issue #52832, Segfault when playing baked particle + explode simulation
1 changed files with 22 additions and 18 deletions
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40
source/blender/blenlib/intern/polyfill2d_beautify.c
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@ -121,6 +121,10 @@ BLI_INLINE bool is_boundary_edge(unsigned int i_a, unsigned int i_b, const unsig
* Assuming we have 2 triangles sharing an edge (2 - 4),
* check if the edge running from (1 - 3) gives better results.
*
* \param lock_degenerate: Use to avoid rotating out of a degenerate state.
* - When true, an existing zero area face on either side of the (2 - 4) split will return a positive value.
* - When false, the check must be non-biased towards either split direction.
*
* \return (negative number means the edge can be rotated, lager == better).
*/
float BLI_polyfill_beautify_quad_rotate_calc_ex(
@ -129,8 +133,6 @@ float BLI_polyfill_beautify_quad_rotate_calc_ex(
{
/* not a loop (only to be able to break out) */
do {
bool is_zero_a, is_zero_b;
const float area_2x_234 = cross_tri_v2(v2, v3, v4);
const float area_2x_241 = cross_tri_v2(v2, v4, v1);
@ -142,25 +144,27 @@ float BLI_polyfill_beautify_quad_rotate_calc_ex(
(ELEM(v3, v1, v2, v4) == false) &&
(ELEM(v4, v1, v2, v3) == false));
if (lock_degenerate) {
is_zero_a = (fabsf(area_2x_234) <= FLT_EPSILON);
is_zero_b = (fabsf(area_2x_241) <= FLT_EPSILON);
/*
* Test for unusable (1-3) state.
* - Area sign flipping to check faces aren't going to point in opposite directions.
* - Area epsilon check that the one of the faces won't be zero area.
*/
if (((area_2x_123 >= 0.0f) != (area_2x_134 >= 0.0f)) ||
(fabsf(area_2x_123) <= FLT_EPSILON) || (fabsf(area_2x_134) <= FLT_EPSILON))
{
break;
}
if (is_zero_a && is_zero_b) {
/* Test for unusable (2-4) state (same as above). */
if (((area_2x_234 >= 0.0f) != (area_2x_241 >= 0.0f)) ||
((fabsf(area_2x_234) <= FLT_EPSILON) || (fabsf(area_2x_241) <= FLT_EPSILON)))
{
if (lock_degenerate) {
break;
}
}
/* one of the tri's was degenerate, check we're not rotating
* into a different degenerate shape or flipping the face */
if ((fabsf(area_2x_123) <= FLT_EPSILON) || (fabsf(area_2x_134) <= FLT_EPSILON)) {
/* one of the new rotations is degenerate */
break;
}
if ((area_2x_123 >= 0.0f) != (area_2x_134 >= 0.0f)) {
/* rotation would cause flipping */
break;
else {
return -FLT_MAX; /* always rotate */
}
}
{