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Fix T85508: UV select overlap fails on identical faces

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The triangle overlap test failed for exactly overlapping triangles.

When none of the segments intersect, testing a if a single corner
is inside the other triangle fails when the triangles share UV
coordinates.

Resolve by comparing the triangle centers.
This commit is contained in:
Campbell Barton
2021-02-11 08:27:47 +11:00
parent 4719836eca
commit 2d252b6d26
1 changed files with 46 additions and 18 deletions
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64
source/blender/editors/uvedit/uvedit_select.c
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@@ -3546,6 +3546,51 @@ struct UVOverlapData {
float tri[3][2];
};
/**
* Specialized 2D triangle intersection for detecting UV overlap:
*
* \return
* - false when single corners or edges touch (common for UV coordinates).
* - true when all corners touch (an exactly overlapping triangle).
*/
static bool overlap_tri_tri_uv_test(const float t1[3][2],
const float t2[3][2],
const float endpoint_bias)
{
float vi[2];
/* Don't use 'isect_tri_tri_v2' here
* because it's important to ignore overlap at end-points. */
if (isect_seg_seg_v2_point_ex(t1[0], t1[1], t2[0], t2[1], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[0], t1[1], t2[1], t2[2], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[0], t1[1], t2[2], t2[0], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[1], t1[2], t2[0], t2[1], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[1], t1[2], t2[1], t2[2], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[1], t1[2], t2[2], t2[0], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[2], t1[0], t2[0], t2[1], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[2], t1[0], t2[1], t2[2], endpoint_bias, vi) == 1) {
return true;
}
/* When none of the segments intersect, checking if either of the triangles corners
* is inside the others is almost always sufficient to test if the two triangles intersect.
*
* However, the `endpoint_bias` on segment intersections causes _exact_ overlapping
* triangles not to be detected.
*
* Resolve this problem at the small cost of calculating the triangle center, see T85508. */
mid_v2_v2v2v2(vi, UNPACK3(t1));
if (isect_point_tri_v2(vi, UNPACK3(t2)) != 0) {
return true;
}
mid_v2_v2v2v2(vi, UNPACK3(t2));
if (isect_point_tri_v2(vi, UNPACK3(t1)) != 0) {
return true;
}
return false;
}
static int uv_select_overlap(bContext *C, const bool extend)
{
Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
@@ -3689,24 +3734,7 @@ static int uv_select_overlap(bContext *C, const bool extend)
/* Main tri-tri overlap test. */
const float endpoint_bias = -1e-4f;
const float(*t1)[2] = o_a->tri;
const float(*t2)[2] = o_b->tri;
float vi[2];
bool result = (
/* Don't use 'isect_tri_tri_v2' here
* because it's important to ignore overlap at end-points. */
isect_seg_seg_v2_point_ex(t1[0], t1[1], t2[0], t2[1], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[0], t1[1], t2[1], t2[2], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[0], t1[1], t2[2], t2[0], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[1], t1[2], t2[0], t2[1], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[1], t1[2], t2[1], t2[2], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[1], t1[2], t2[2], t2[0], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[2], t1[0], t2[0], t2[1], endpoint_bias, vi) == 1 ||
isect_seg_seg_v2_point_ex(t1[2], t1[0], t2[1], t2[2], endpoint_bias, vi) == 1 ||
isect_point_tri_v2(t1[0], t2[0], t2[1], t2[2]) != 0 ||
isect_point_tri_v2(t2[0], t1[0], t1[1], t1[2]) != 0);
if (result) {
if (overlap_tri_tri_uv_test(o_a->tri, o_b->tri, endpoint_bias)) {
uvedit_face_select_enable(scene, em_a, face_a, false, cd_loop_uv_offset_a);
uvedit_face_select_enable(scene, em_b, face_b, false, cd_loop_uv_offset_b);
}