EditNormal modifier: add some 'maximum angle' limit.

Allows to avoid generating flipped faces when using extreme normal modifications.

Related to T48576.

release/scripts/startup/bl_ui/properties_data_modifier.py

@@ -1418,6 +1418,7 @@ class DATA_PT_modifiers(ModifierButtonsPanel, Panel):
         sub = row.row(align=True)
         sub.active = has_vgroup
         sub.prop(md, "invert_vertex_group", text="", icon='ARROW_LEFTRIGHT')
+        subcol.prop(md, "mix_limit")
 
     def CORRECTIVE_SMOOTH(self, layout, ob, md):
         is_bind = md.is_bind

source/blender/blenloader/intern/versioning_270.c

@@ -1189,9 +1189,7 @@ void blo_do_versions_270(FileData *fd, Library *UNUSED(lib), Main *main)
 				}
 			}
 		}
-	}
 
-	{
 		for (Camera *camera = main->camera.first; camera != NULL; camera = camera->id.next) {
 			if (camera->stereo.pole_merge_angle_from == 0.0f &&
 			    camera->stereo.pole_merge_angle_to == 0.0f)
@@ -1200,5 +1198,19 @@ void blo_do_versions_270(FileData *fd, Library *UNUSED(lib), Main *main)
 				camera->stereo.pole_merge_angle_to = DEG2RAD(75.0f);
 			}
 		}
+
+		if (!DNA_struct_elem_find(fd->filesdna, "NormalEditModifierData", "float", "mix_limit")) {
+			Object *ob;
+
+			for (ob = main->object.first; ob; ob = ob->id.next) {
+				ModifierData *md;
+				for (md = ob->modifiers.first; md; md = md->next) {
+					if (md->type == eModifierType_NormalEdit) {
+						NormalEditModifierData *nemd = (NormalEditModifierData *)md;
+						nemd->mix_limit = DEG2RADF(180.0f);
+					}
+				}
+			}
+		}
 	}
 }

source/blender/makesdna/DNA_modifier_types.h

@@ -1518,7 +1518,9 @@ typedef struct NormalEditModifierData {
 	short mix_mode;
 	char pad[2];
 	float mix_factor;
+	float mix_limit;
 	float offset[3];
+	float pad_f1;
 } NormalEditModifierData;
 
 /* NormalEditModifierData.mode */

source/blender/makesrna/intern/rna_modifier.c

@@ -4602,6 +4602,11 @@ static void rna_def_modifier_normaledit(BlenderRNA *brna)
 	                     "How much of generated normals to mix with exiting ones", 0.0f, 1.0f);
 	RNA_def_property_update(prop, 0, "rna_Modifier_update");
 
+	prop = RNA_def_float(srna, "mix_limit", 1.0f, 0.0f, DEG2RADF(180.0f), "Max Angle",
+	                     "Maximum angle between old and new normals", 0.0f, DEG2RADF(180.0f));
+	RNA_def_property_subtype(prop, PROP_ANGLE);
+	RNA_def_property_update(prop, 0, "rna_Modifier_update");
+
 	prop = RNA_def_property(srna, "vertex_group", PROP_STRING, PROP_NONE);
 	RNA_def_property_string_sdna(prop, NULL, "defgrp_name");
 	RNA_def_property_ui_text(prop, "Vertex Group", "Vertex group name for selecting/weighting the affected areas");

source/blender/modifiers/intern/MOD_normal_edit.c

@@ -110,7 +110,7 @@ static void generate_vert_coordinates(
 /* Note this modifies nos_new in-place. */
 static void mix_normals(
         const float mix_factor, MDeformVert *dvert, const int defgrp_index, const bool use_invert_vgroup,
-        const short mix_mode,
+        const float mix_limit, const short mix_mode,
         const int num_verts, MLoop *mloop, float (*nos_old)[3], float (*nos_new)[3], const int num_loops)
 {
 	/* Mix with org normals... */
@@ -143,7 +143,9 @@ static void mix_normals(
 			case MOD_NORMALEDIT_MIX_COPY:
 				break;
 		}
-		interp_v3_v3v3_slerp_safe(*no_new, *no_old, *no_new, fac);
+
+		interp_v3_v3v3_slerp_safe(*no_new, *no_old, *no_new,
+		                          (mix_limit < M_PI) ? min_ff(fac, mix_limit / angle_v3v3(*no_new, *no_old)) : fac);
 	}
 
 	MEM_SAFE_FREE(facs);
@@ -186,7 +188,7 @@ static bool polygons_check_flip(
 static void normalEditModifier_do_radial(
         NormalEditModifierData *smd, Object *ob, DerivedMesh *dm,
         short (*clnors)[2], float (*loopnors)[3], float (*polynors)[3],
-        const short mix_mode, const float mix_factor,
+        const short mix_mode, const float mix_factor, const float mix_limit,
         MDeformVert *dvert, const int defgrp_index, const bool use_invert_vgroup,
         MVert *mvert, const int num_verts, MEdge *medge, const int num_edges,
         MLoop *mloop, const int num_loops, MPoly *mpoly, const int num_polys)
@@ -265,7 +267,7 @@ static void normalEditModifier_do_radial(
 
 	if (loopnors) {
 		mix_normals(mix_factor, dvert, defgrp_index, use_invert_vgroup,
-		            mix_mode, num_verts, mloop, loopnors, nos, num_loops);
+		            mix_limit, mix_mode, num_verts, mloop, loopnors, nos, num_loops);
 	}
 
 	if (polygons_check_flip(mloop, nos, dm->getLoopDataLayout(dm), mpoly, polynors, num_polys)) {
@@ -283,7 +285,7 @@ static void normalEditModifier_do_radial(
 static void normalEditModifier_do_directional(
         NormalEditModifierData *smd, Object *ob, DerivedMesh *dm,
         short (*clnors)[2], float (*loopnors)[3], float (*polynors)[3],
-        const short mix_mode, const float mix_factor,
+        const short mix_mode, const float mix_factor, const float mix_limit,
         MDeformVert *dvert, const int defgrp_index, const bool use_invert_vgroup,
         MVert *mvert, const int num_verts, MEdge *medge, const int num_edges,
         MLoop *mloop, const int num_loops, MPoly *mpoly, const int num_polys)
@@ -342,7 +344,7 @@ static void normalEditModifier_do_directional(
 
 	if (loopnors) {
 		mix_normals(mix_factor, dvert, defgrp_index, use_invert_vgroup,
-		            mix_mode, num_verts, mloop, loopnors, nos, num_loops);
+		            mix_limit, mix_mode, num_verts, mloop, loopnors, nos, num_loops);
 	}
 
 	if (polygons_check_flip(mloop, nos, dm->getLoopDataLayout(dm), mpoly, polynors, num_polys)) {
@@ -384,7 +386,8 @@ static DerivedMesh *normalEditModifier_do(NormalEditModifierData *smd, Object *o
 	const bool use_invert_vgroup = ((smd->flag & MOD_NORMALEDIT_INVERT_VGROUP) != 0);
 	const bool use_current_clnors = !((smd->mix_mode == MOD_NORMALEDIT_MIX_COPY) &&
 	                                  (smd->mix_factor == 1.0f) &&
-	                                  (smd->defgrp_name[0] == '\0'));
+	                                  (smd->defgrp_name[0] == '\0') &&
+	                                  (smd->mix_limit == M_PI));
 
 	int defgrp_index;
 	MDeformVert *dvert;
@@ -439,13 +442,13 @@ static DerivedMesh *normalEditModifier_do(NormalEditModifierData *smd, Object *o
 	if (smd->mode == MOD_NORMALEDIT_MODE_RADIAL) {
 		normalEditModifier_do_radial(
 		            smd, ob, dm, clnors, loopnors, polynors,
-		            smd->mix_mode, smd->mix_factor, dvert, defgrp_index, use_invert_vgroup,
+		            smd->mix_mode, smd->mix_factor, smd->mix_limit, dvert, defgrp_index, use_invert_vgroup,
 		            mvert, num_verts, medge, num_edges, mloop, num_loops, mpoly, num_polys);
 	}
 	else if (smd->mode == MOD_NORMALEDIT_MODE_DIRECTIONAL) {
 		normalEditModifier_do_directional(
 		            smd, ob, dm, clnors, loopnors, polynors,
-		            smd->mix_mode, smd->mix_factor, dvert, defgrp_index, use_invert_vgroup,
+		            smd->mix_mode, smd->mix_factor, smd->mix_limit, dvert, defgrp_index, use_invert_vgroup,
 		            mvert, num_verts, medge, num_edges, mloop, num_loops, mpoly, num_polys);
 	}
 
@@ -464,6 +467,7 @@ static void initData(ModifierData *md)
 
 	smd->mix_mode = MOD_NORMALEDIT_MIX_COPY;
 	smd->mix_factor = 1.0f;
+	smd->mix_limit = M_PI;
 }
 
 static void copyData(ModifierData *md, ModifierData *target)