Fix bug where corner boundary was straight when it should curve.

Some adjustments to how bevel edge 'profiles' are adjusted in some
cases. For the bug fix, wanted to handle cases of middle of three
coplanar beveled cases to make profile curve rather than linear
interpolate.
Also undid an earlier decision to make profile plane be perpendicular
to beveled edge i the non-coplanar case.

1 files changed, 58 insertions, 17 deletions

diff --git a/source/blender/bmesh/tools/bmesh_bevel.c b/source/blender/bmesh/tools/bmesh_bevel.c
index f7e3622e53c..0ed1dffcafb 100644
--- a/source/blender/bmesh/tools/bmesh_bevel.c
+++ b/source/blender/bmesh/tools/bmesh_bevel.c
@@ -198,6 +198,12 @@ typedef struct BevelParams {
 
 // #include "bevdebug.c"
 
+/* some flags to re-enable old behavior for a while, in case fixes broke things not caught by regression tests */
+static int bev_debug_flags = 0;
+#define DEBUG_OLD_PLANE_SPECIAL (bev_debug_flags & 1)
+#define DEBUG_OLD_PROJ_TO_PERP_PLANE (bev_debug_flags & 2)
+#define DEBUG_OLD_FLAT_MID (bev_debug_flags & 4)
+
 /* Make a new BoundVert of the given kind, insert it at the end of the circular linked
  * list with entry point bv->boundstart, and return it. */
 static BoundVert *add_new_bound_vert(MemArena *mem_arena, VMesh *vm, const float co[3])
@@ -1045,15 +1051,21 @@ static void set_profile_params(BevelParams *bp, BevVert *bv, BoundVert *bndv)
 		sub_v3_v3v3(pro->proj_dir, e->e->v1->co, e->e->v2->co);
 		normalize_v3(pro->proj_dir);
 		project_to_edge(e->e, co1, co2, pro->midco);
-		/* put arc endpoints on plane with normal proj_dir, containing midco */
-		add_v3_v3v3(co3, co1, pro->proj_dir);
-		if (!isect_line_plane_v3(pro->coa, co1, co3, pro->midco, pro->proj_dir)) {
-			/* shouldn't happen */
-			copy_v3_v3(pro->coa, co1);
+		if (DEBUG_OLD_PROJ_TO_PERP_PLANE) {
+			/* put arc endpoints on plane with normal proj_dir, containing midco */
+			add_v3_v3v3(co3, co1, pro->proj_dir);
+			if (!isect_line_plane_v3(pro->coa, co1, co3, pro->midco, pro->proj_dir)) {
+				/* shouldn't happen */
+				copy_v3_v3(pro->coa, co1);
+			}
+			add_v3_v3v3(co3, co2, pro->proj_dir);
+			if (!isect_line_plane_v3(pro->cob, co2, co3, pro->midco, pro->proj_dir)) {
+				/* shouldn't happen */
+				copy_v3_v3(pro->cob, co2);
+			}
 		}
-		add_v3_v3v3(co3, co2, pro->proj_dir);
-		if (!isect_line_plane_v3(pro->cob, co2, co3, pro->midco, pro->proj_dir)) {
-			/* shouldn't happen */
+		else {
+			copy_v3_v3(pro->coa, co1);
 			copy_v3_v3(pro->cob, co2);
 		}
 		/* default plane to project onto is the one with triangle co1 - midco - co2 in it */
@@ -1066,19 +1078,48 @@ static void set_profile_params(BevelParams *bp, BevVert *bv, BoundVert *bndv)
 		if (l  <= BEVEL_EPSILON_BIG) {
 			/* co1 - midco -co2 are collinear.
 			 * Should be case that beveled edge is coplanar with two boundary verts.
+			 * We want to move the profile to that common plane, if possible.
+			 * That makes the multi-segment bevels curve nicely in that plane, as users expect.
+			 * The new midco should be either v (when neighbor edges are unbeveled)
+			 * or the intersection of the offset lines (if they are).
 			 * If the profile is going to lead into unbeveled edges on each side
 			 * (that is, both BoundVerts are "on-edge" points on non-beveled edges)
-			 * then in order to get curve in multi-segment case, change projection plane
-			 * to be that common plane, projection dir to be the plane normal,
-			 * and mid to be the original vertex.
-			 * Otherwise, we just want to linearly interpolate between co1 and co2.
 			 */
-			if (e->prev->is_bev || e->next->is_bev) {
+			if (DEBUG_OLD_PLANE_SPECIAL && (e->prev->is_bev || e->next->is_bev)) {
 				do_linear_interp = true;
 			}
 			else {
-				copy_v3_v3(pro->coa, co1);
-				copy_v3_v3(pro->midco, bv->v->co);
+				if (DEBUG_OLD_PROJ_TO_PERP_PLANE) {
+					copy_v3_v3(pro->coa, co1);
+					copy_v3_v3(pro->cob, co2);
+				}
+				if (DEBUG_OLD_FLAT_MID) {
+					copy_v3_v3(pro->midco, bv->v->co);
+				}
+				else {
+					copy_v3_v3(pro->midco, bv->v->co);
+					if (e->prev->is_bev && e->next->is_bev && bv->selcount >= 3) {
+						/* want mid at the meet point of next and prev offset edges */
+						float d3[3], d4[3], co4[3], meetco[3], isect2[3];
+						int isect_kind;
+
+						sub_v3_v3v3(d3, e->prev->e->v1->co, e->prev->e->v2->co);
+						sub_v3_v3v3(d4, e->next->e->v1->co, e->next->e->v2->co);
+						normalize_v3(d3);
+						normalize_v3(d4);
+						add_v3_v3v3(co3, co1, d3);
+						add_v3_v3v3(co4, co2, d4);
+						isect_kind = isect_line_line_v3(co1, co3, co2, co4, meetco, isect2);
+						if (isect_kind != 0) {
+							copy_v3_v3(pro->midco, meetco);
+						}
+						else {
+							/* offset lines are collinear - want linear interpolation */
+							mid_v3_v3v3(pro->midco, co1, co2);
+							do_linear_interp = true;
+						}
+					}
+				}
 				copy_v3_v3(pro->cob, co2);
 				sub_v3_v3v3(d1, pro->midco, co1);
 				normalize_v3(d1);
@@ -3436,7 +3477,7 @@ static bool fast_bevel_edge_order(BevVert *bv)
 			}
 		}
 		if (nsucs == 0 || (nsucs == 2 && j != 1) || nsucs > 2 ||
-			(j == bv->edgecount - 1 && !edges_face_connected_at_vert(bmenext, bv->edges[0].e)))
+		    (j == bv->edgecount - 1 && !edges_face_connected_at_vert(bmenext, bv->edges[0].e)))
 		{
 			for (k = 1; k < j; k++) {
 				BM_BEVEL_EDGE_TAG_DISABLE(bv->edges[k].e);
@@ -3868,7 +3909,7 @@ static bool bev_rebuild_polygon(BMesh *bm, BevelParams *bp, BMFace *f)
 					/* going cw */
 					if (vm->seg > 1) {
 						if (vm->mesh_kind == M_ADJ || bp->vertex_only ||
-							(vm->mesh_kind == M_NONE && v->ebev != e && v->ebev != eprev))
+						    (vm->mesh_kind == M_NONE && v->ebev != e && v->ebev != eprev))
 						{
 							i = v->prev->index;
 							for (k = vm->seg - 1; k > 0; k--) {