add option for decimate-collapse to keep triangulated geometry (normally quads stay as quads when not collapsed).

5 files changed, 18 insertions, 8 deletions

diff --git a/source/blender/bmesh/intern/bmesh_decimate.h b/source/blender/bmesh/intern/bmesh_decimate.h
index 04aa392fcf0..a5f4acc5f37 100644
--- a/source/blender/bmesh/intern/bmesh_decimate.h
+++ b/source/blender/bmesh/intern/bmesh_decimate.h
@@ -27,7 +27,7 @@
  *  \ingroup bmesh
  */
 
-void BM_mesh_decimate_collapse(BMesh *bm, const float factor, float *vweights);
+void BM_mesh_decimate_collapse(BMesh *bm, const float factor, float *vweights, const int do_triangulate);
 
 void BM_mesh_decimate_unsubdivide_ex(BMesh *bm, const int iterations, const int tag_only);
 void BM_mesh_decimate_unsubdivide(BMesh *bm, const int iterations);
diff --git a/source/blender/bmesh/intern/bmesh_decimate_collapse.c b/source/blender/bmesh/intern/bmesh_decimate_collapse.c
index ce10fe2fed1..cbc7c0dac9d 100644
--- a/source/blender/bmesh/intern/bmesh_decimate_collapse.c
+++ b/source/blender/bmesh/intern/bmesh_decimate_collapse.c
@@ -855,7 +855,7 @@ static void bm_decim_edge_collapse(BMesh *bm, BMEdge *e,
  * \param vertex_weights Optional array of vertex  aligned weights [0 - 1],
  *        a vertex group is the usual source for this.
  */
-void BM_mesh_decimate_collapse(BMesh *bm, const float factor, float *vweights)
+void BM_mesh_decimate_collapse(BMesh *bm, const float factor, float *vweights, const int do_triangulate)
 {
 	Heap *eheap;             /* edge heap */
 	HeapNode **eheap_table;  /* edge index aligned table pointing to the eheap */
@@ -913,10 +913,12 @@ void BM_mesh_decimate_collapse(BMesh *bm, const float factor, float *vweights)
 
 
 #ifdef USE_TRIANGULATE
-	/* its possible we only had triangles, skip this step in that case */
-	if (LIKELY(use_triangulate)) {
-		/* temp convert quads to triangles */
-		bm_decim_triangulate_end(bm);
+	if (do_triangulate == FALSE) {
+		/* its possible we only had triangles, skip this step in that case */
+		if (LIKELY(use_triangulate)) {
+			/* temp convert quads to triangles */
+			bm_decim_triangulate_end(bm);
+		}
 	}
 #endif
 
diff --git a/source/blender/makesdna/DNA_modifier_types.h b/source/blender/makesdna/DNA_modifier_types.h
index 6853eefd2ec..477d2c28f7c 100644
--- a/source/blender/makesdna/DNA_modifier_types.h
+++ b/source/blender/makesdna/DNA_modifier_types.h
@@ -374,7 +374,8 @@ typedef struct DecimateModifierData {
 } DecimateModifierData;
 
 enum {
-	MOD_DECIM_FLAG_INVERT_VGROUP = (1 << 0)
+	MOD_DECIM_FLAG_INVERT_VGROUP = (1 << 0),
+	MOD_DECIM_FLAG_TRIANGULATE   = (1 << 1)   /* for collapse only. dont convert tri pairs back to quads */
 };
 
 enum {
diff --git a/source/blender/makesrna/intern/rna_modifier.c b/source/blender/makesrna/intern/rna_modifier.c
index 47212c4a231..12254a62f71 100644
--- a/source/blender/makesrna/intern/rna_modifier.c
+++ b/source/blender/makesrna/intern/rna_modifier.c
@@ -1166,6 +1166,11 @@ static void rna_def_modifier_decimate(BlenderRNA *brna)
 	RNA_def_property_boolean_sdna(prop, NULL, "flag", MOD_DECIM_FLAG_INVERT_VGROUP);
 	RNA_def_property_ui_text(prop, "Invert", "Invert vertex group influence");
 	RNA_def_property_update(prop, 0, "rna_Modifier_update");
+
+	prop = RNA_def_property(srna, "use_triangulate", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", MOD_DECIM_FLAG_TRIANGULATE);
+	RNA_def_property_ui_text(prop, "Triangulate", "Keep triangulated faces resulting from decimation");
+	RNA_def_property_update(prop, 0, "rna_Modifier_update");
 	/* end collapse-only option */
 
 	/* all modes use this */
diff --git a/source/blender/modifiers/intern/MOD_decimate.c b/source/blender/modifiers/intern/MOD_decimate.c
index 71b3b6c883b..cb6eb127172 100644
--- a/source/blender/modifiers/intern/MOD_decimate.c
+++ b/source/blender/modifiers/intern/MOD_decimate.c
@@ -100,6 +100,8 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
 	BMEditMesh *em;
 	BMesh *bm;
 
+	const int do_triangulate = (dmd->flag & MOD_DECIM_FLAG_TRIANGULATE) != 0;
+
 	float *vweights = NULL;
 
 #ifdef USE_TIMEIT
@@ -146,7 +148,7 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
 
 	switch (dmd->mode) {
 		case MOD_DECIM_MODE_COLLAPSE:
-			BM_mesh_decimate_collapse(bm, dmd->percent, vweights);
+			BM_mesh_decimate_collapse(bm, dmd->percent, vweights, do_triangulate);
 			break;
 		case MOD_DECIM_MODE_UNSUBDIV:
 			BM_mesh_decimate_unsubdivide(bm, dmd->iter);