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Fix T45123: 2D line intersection fails 

Co-linear lines could detect as intersecting even if they weren't overlapping.
This commit is contained in:
Campbell Barton 2015-06-23 20:37:53 +10:00
parent ec8e0336a9
commit 72e812de7c
Notes: blender-bot 2023-02-14 08:59:13 +01:00 
Referenced by issue #45123, Mysterious goings-on in the Movie Clip Editor (or is it the Compositor?)
1 changed files with 20 additions and 2 deletions
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22
source/blender/blenlib/intern/math_geom.c
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@ -719,8 +719,26 @@ int isect_seg_seg_v2_point(const float v0[2], const float v1[2], const float v2[
(v >= -eps && v <= 1.0f + eps))
{
/* intersection */
madd_v2_v2v2fl(r_vi, v0, s10, u);
return 1;
float vi_test[2];
float s_vi_v2[2];
madd_v2_v2v2fl(vi_test, v0, s10, u);
/* When 'd' approaches zero, float precision lets non-overlapping co-linear segments
* detect as an intersection. So re-calculate 'v' to ensure the point overlaps both.
* see T45123 */
/* inline since we have most vars already */
#if 0
v = line_point_factor_v2(ix_test, v2, v3);
#else
sub_v2_v2v2(s_vi_v2, vi_test, v2);
v = (dot_v2v2(s32, s_vi_v2) / dot_v2v2(s32, s32));
#endif
if (v >= -eps && v <= 1.0f + eps) {
copy_v2_v2(r_vi, vi_test);
return 1;
}
}
/* out of segment intersection */