Bevel: partial fix for distortion (bug 33280).

Sometimes it is impossible to have same offset from
both edges that are on angled faces. The fix here
at least doesn't distort the non-beveled part of the
model, and looks much better than before on bug
example, but is still not perfect.

1 files changed, 27 insertions, 10 deletions

diff --git a/source/blender/bmesh/tools/bmesh_bevel.c b/source/blender/bmesh/tools/bmesh_bevel.c
index 0d16d0af114..62465ea9849 100644
--- a/source/blender/bmesh/tools/bmesh_bevel.c
+++ b/source/blender/bmesh/tools/bmesh_bevel.c
@@ -365,13 +365,19 @@ static void offset_meet(EdgeHalf *e1, EdgeHalf *e2, BMVert *v, BMFace *f,
 }
 
 /* Like offset_meet, but here f1 and f2 must not be NULL and give the
- * planes in which to run the offset lines.  They may not meet exactly,
- * but the line intersection routine will find the closest approach point. */
-static void offset_in_two_planes(EdgeHalf *e1, EdgeHalf *e2, BMVert *v,
-                                 BMFace *f1, BMFace *f2, float meetco[3])
+ * planes in which to run the offset lines.
+ * They may not meet exactly: the offsets for the edges may be different
+ * or both the planes and the lines may be angled so that they can't meet.
+ * In that case, pick a close point on emid, which should be the dividing
+ * edge between the two planes.
+ * TODO: should have a global 'offset consistency' prepass to adjust offset
+ * widths so that all edges have the same offset at both ends. */
+static void offset_in_two_planes(EdgeHalf *e1, EdgeHalf *e2, EdgeHalf *emid,
+                                 BMVert *v, BMFace *f1, BMFace *f2, float meetco[3])
 {
 	float dir1[3], dir2[3], norm_perp1[3], norm_perp2[3],
-	      off1a[3], off1b[3], off2a[3], off2b[3], isect2[3];
+	      off1a[3], off1b[3], off2a[3], off2b[3], isect2[3], co[3];
+	int iret;
 
 	BLI_assert(f1 != NULL && f2 != NULL);
 
@@ -397,9 +403,21 @@ static void offset_in_two_planes(EdgeHalf *e1, EdgeHalf *e2, BMVert *v,
 		/* lines are parallel; off1a is a good meet point */
 		copy_v3_v3(meetco, off1a);
 	}
-	else if (!isect_line_line_v3(off1a, off1b, off2a, off2b, meetco, isect2)) {
-		/* another test says they are parallel */
-		copy_v3_v3(meetco, off1a);
+	else {
+		iret =isect_line_line_v3(off1a, off1b, off2a, off2b, meetco, isect2);
+		if (iret == 0) {
+			/* lines colinear: another test says they are parallel. so shouldn't happen */
+			copy_v3_v3(meetco, off1a);
+		}
+		else if (iret == 2) {
+			/* lines are not coplanar; meetco and isect2 are nearest to first and second lines */
+			if (len_v3v3(meetco, isect2) > 100.0f * (float)BEVEL_EPSILON) {
+				/* offset lines don't meet: project average onto emid; this is not ideal (see TODO above) */
+				mid_v3_v3v3(co, meetco, isect2);
+				closest_to_line_v3(meetco, co, v->co, BM_edge_other_vert(emid->e, v)->co);
+			}
+		}
+		/* else iret == 1 and the lines are coplanar so meetco has the intersection */
 	}
 }
 
@@ -753,8 +771,7 @@ static void build_boundary(MemArena *mem_arena, BevVert *bv)
 				if (e->prev->prev->is_bev) {
 					BLI_assert(e->prev->prev != e); /* see: edgecount 2, selcount 1 case */
 					/* find meet point between e->prev->prev and e and attach e->prev there */
-					/* TODO: fix case when one or both faces in following are NULL */
-					offset_in_two_planes(e->prev->prev, e, bv->v,
+					offset_in_two_planes(e->prev->prev, e, e->prev, bv->v,
 					                     e->prev->prev->fnext, e->fprev, co);
 					v = add_new_bound_vert(mem_arena, vm, co);
 					v->efirst = e->prev->prev;