Fix T44780: Decimate planar creates concave edges

Float precision was causing problems for decimate,
small faces that create a nearly flat surface were detected as having no 'cost' to collapse.

3 files changed, 42 insertions, 40 deletions

diff --git a/source/blender/blenlib/BLI_quadric.h b/source/blender/blenlib/BLI_quadric.h
index 251469ab88f..eaf9c7a0738 100644
--- a/source/blender/blenlib/BLI_quadric.h
+++ b/source/blender/blenlib/BLI_quadric.h
@@ -31,14 +31,14 @@
  */
 
 typedef struct Quadric {
-	float a2, ab, ac, ad,
-	          b2, bc, bd,
-	              c2, cd,
-	                  d2;
+	double a2, ab, ac, ad,
+	           b2, bc, bd,
+	               c2, cd,
+	                   d2;
 } Quadric;
 
 /* conversion */
-void  BLI_quadric_from_plane(Quadric *q, const float v[4]);
+void  BLI_quadric_from_plane(Quadric *q, const double v[4]);
 void  BLI_quadric_to_tensor_m3(const Quadric *q, float m[3][3]);
 void  BLI_quadric_to_vector_v3(const Quadric *q, float v[3]);
 
@@ -47,10 +47,10 @@ void  BLI_quadric_clear(Quadric *q);
 /* math */
 void  BLI_quadric_add_qu_qu(Quadric *a, const Quadric *b);
 void  BLI_quadric_add_qu_ququ(Quadric *r, const Quadric *a, const Quadric *b);
-void  BLI_quadric_mul(Quadric *a, const float scalar);
+void  BLI_quadric_mul(Quadric *a, const double scalar);
 
 /* solve */
-float BLI_quadric_evaluate(const Quadric *q, const float v[3]);
+double BLI_quadric_evaluate(const Quadric *q, const float v_fl[3]);
 bool  BLI_quadric_optimize(const Quadric *q, float v[3], const float epsilon);
 
 #endif /* __BLI_QUADRIC_H__ */
diff --git a/source/blender/blenlib/intern/quadric.c b/source/blender/blenlib/intern/quadric.c
index 4aa0cdd509d..c1abacee42e 100644
--- a/source/blender/blenlib/intern/quadric.c
+++ b/source/blender/blenlib/intern/quadric.c
@@ -32,17 +32,15 @@
  * \note try to follow BLI_math naming convention here.
  */
 
-//#include <string.h>
-
 #include "BLI_math.h"
 #include "BLI_strict_flags.h"
 
 #include "BLI_quadric.h"  /* own include */
 
 
-#define QUADRIC_FLT_TOT (sizeof(Quadric) / sizeof(float))
+#define QUADRIC_FLT_TOT (sizeof(Quadric) / sizeof(double))
 
-void BLI_quadric_from_plane(Quadric *q, const float v[4])
+void BLI_quadric_from_plane(Quadric *q, const double v[4])
 {
 	q->a2 = v[0] * v[0];
 	q->b2 = v[1] * v[1];
@@ -61,24 +59,24 @@ void BLI_quadric_from_plane(Quadric *q, const float v[4])
 
 void BLI_quadric_to_tensor_m3(const Quadric *q, float m[3][3])
 {
-	m[0][0] = q->a2;
-	m[0][1] = q->ab;
-	m[0][2] = q->ac;
+	m[0][0] = (float)q->a2;
+	m[0][1] = (float)q->ab;
+	m[0][2] = (float)q->ac;
 
-	m[1][0] = q->ab;
-	m[1][1] = q->b2;
-	m[1][2] = q->bc;
+	m[1][0] = (float)q->ab;
+	m[1][1] = (float)q->b2;
+	m[1][2] = (float)q->bc;
 
-	m[2][0] = q->ac;
-	m[2][1] = q->bc;
-	m[2][2] = q->c2;
+	m[2][0] = (float)q->ac;
+	m[2][1] = (float)q->bc;
+	m[2][2] = (float)q->c2;
 }
 
 void BLI_quadric_to_vector_v3(const Quadric *q, float v[3])
 {
-	v[0] = q->ad;
-	v[1] = q->bd;
-	v[2] = q->cd;
+	v[0] = (float)q->ad;
+	v[1] = (float)q->bd;
+	v[2] = (float)q->cd;
 }
 
 void BLI_quadric_clear(Quadric *q)
@@ -88,25 +86,26 @@ void BLI_quadric_clear(Quadric *q)
 
 void BLI_quadric_add_qu_qu(Quadric *a, const Quadric *b)
 {
-	add_vn_vn((float *)a, (float *)b, QUADRIC_FLT_TOT);
+	add_vn_vn_d((double *)a, (double *)b, QUADRIC_FLT_TOT);
 }
 
 void BLI_quadric_add_qu_ququ(Quadric *r, const Quadric *a, const Quadric *b)
 {
-	add_vn_vnvn((float *)r, (const float *)a, (const float *)b, QUADRIC_FLT_TOT);
+	add_vn_vnvn_d((double *)r, (const double *)a, (const double *)b, QUADRIC_FLT_TOT);
 }
 
-void BLI_quadric_mul(Quadric *a, const float scalar)
+void BLI_quadric_mul(Quadric *a, const double scalar)
 {
-	mul_vn_fl((float *)a, QUADRIC_FLT_TOT, scalar);
+	mul_vn_db((double *)a, QUADRIC_FLT_TOT, scalar);
 }
 
-float BLI_quadric_evaluate(const Quadric *q, const float v[3])
+double BLI_quadric_evaluate(const Quadric *q, const float v_fl[3])
 {
-	return  (v[0] * v[0] * q->a2 + 2.0f * v[0] * v[1] * q->ab + 2.0f * v[0] * v[2] * q->ac + 2.0f * v[0] * q->ad +
-	         v[1] * v[1] * q->b2 + 2.0f * v[1] * v[2] * q->bc + 2.0f * v[1] * q->bd +
-	         v[2] * v[2] * q->c2 + 2.0f * v[2] * q->cd +
-	         q->d2);
+	const double v[3] = {UNPACK3(v_fl)};
+	return ((q->a2 * v[0] * v[0]) + (q->ab * 2 * v[0] * v[1]) + (q->ac * 2 * v[0] * v[2]) + (q->ad * 2 * v[0]) +
+	        (q->b2 * v[1] * v[1]) + (q->bc * 2 * v[1] * v[2]) + (q->bd * 2 * v[1]) +
+	        (q->c2 * v[2] * v[2]) + (q->cd * 2 * v[2]) +
+	        (q->d2));
 }
 
 bool BLI_quadric_optimize(const Quadric *q, float v[3], const float epsilon)
diff --git a/source/blender/bmesh/tools/bmesh_decimate_collapse.c b/source/blender/bmesh/tools/bmesh_decimate_collapse.c
index fafd4c5ae3f..9b35414f9e6 100644
--- a/source/blender/bmesh/tools/bmesh_decimate_collapse.c
+++ b/source/blender/bmesh/tools/bmesh_decimate_collapse.c
@@ -84,14 +84,14 @@ static void bm_decim_build_quadrics(BMesh *bm, Quadric *vquadrics)
 		BMLoop *l_iter;
 
 		float center[3];
-		float plane[4];
+		double plane_db[4];
 		Quadric q;
 
 		BM_face_calc_center_mean(f, center);
-		copy_v3_v3(plane, f->no);
-		plane[3] = -dot_v3v3(plane, center);
+		copy_v3db_v3fl(plane_db, f->no);
+		plane_db[3] = -dot_v3db_v3fl(plane_db, center);
 
-		BLI_quadric_from_plane(&q, plane);
+		BLI_quadric_from_plane(&q, plane_db);
 
 		l_iter = l_first = BM_FACE_FIRST_LOOP(f);
 		do {
@@ -103,19 +103,22 @@ static void bm_decim_build_quadrics(BMesh *bm, Quadric *vquadrics)
 	BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
 		if (UNLIKELY(BM_edge_is_boundary(e))) {
 			float edge_vector[3];
-			float edge_plane[4];
+			float edge_plane[3];
+			double edge_plane_db[4];
 			sub_v3_v3v3(edge_vector, e->v2->co, e->v1->co);
 			f = e->l->f;
+
 			cross_v3_v3v3(edge_plane, edge_vector, f->no);
+			copy_v3db_v3fl(edge_plane_db, edge_plane);
 
-			if (normalize_v3(edge_plane) > FLT_EPSILON) {
+			if (normalize_v3_d(edge_plane_db) > FLT_EPSILON) {
 				Quadric q;
 				float center[3];
 
 				mid_v3_v3v3(center, e->v1->co, e->v2->co);
-				edge_plane[3] = -dot_v3v3(edge_plane, center);
 
-				BLI_quadric_from_plane(&q, edge_plane);
+				edge_plane_db[3] = -dot_v3db_v3fl(edge_plane_db, center);
+				BLI_quadric_from_plane(&q, edge_plane_db);
 				BLI_quadric_mul(&q, BOUNDARY_PRESERVE_WEIGHT);
 
 				BLI_quadric_add_qu_qu(&vquadrics[BM_elem_index_get(e->v1)], &q);