Yet another tweak to stretch volume variation.

Make sure the 1.0 value is not affected by smoothing, and min/max limits
never go above or below 1.0 respectively. This was a request by
animators since not modifying the mesh in its rest pose is regarded as
crucial.

3 files changed, 54 insertions, 31 deletions

diff --git a/source/blender/blenkernel/intern/constraint.c b/source/blender/blenkernel/intern/constraint.c
index 3a9eb31f061..97515244422 100644
--- a/source/blender/blenkernel/intern/constraint.c
+++ b/source/blender/blenkernel/intern/constraint.c
@@ -2613,6 +2613,8 @@ static void stretchto_new_data(void *cdata)
 	data->plane = 0;
 	data->orglength = 0.0; 
 	data->bulge = 1.0;
+	data->bulge_max = 1.0f;
+	data->bulge_min = 1.0f;
 }
 
 static void stretchto_id_looper(bConstraint *con, ConstraintIDFunc func, void *userdata)
@@ -2689,37 +2691,28 @@ static void stretchto_evaluate(bConstraint *con, bConstraintOb *cob, ListBase *t
 		
 		bulge = powf(data->orglength / dist, data->bulge);
 		
-		if (data->flag & STRETCHTOCON_USE_BULGE_MAX) {
-			const float bulge_median = ((data->flag & STRETCHTOCON_USE_BULGE_MIN) ?
-			                            0.5f * (data->bulge_min + data->bulge_max) : 0.0f);
-			const float bulge_range = data->bulge_max - bulge_median;
-			float bulge_smoothed;
-
-			bulge_smoothed = bulge_median + bulge_range * atanf(bulge - bulge_median) / (0.5f * M_PI);
-
-			if (data->flag & STRETCHTOCON_USE_BULGE_MIN) {
-				CLAMP_MIN(bulge, data->bulge_min);
+		if (bulge > 1.0f) {
+			if (data->flag & STRETCHTOCON_USE_BULGE_MAX) {
+				float bulge_max = max_ff(data->bulge_max, 1.0f);
+				float hard = min_ff(bulge, bulge_max);
+				
+				float range = bulge_max - 1.0f;
+				float scale = (range > 0.0f) ? 1.0f / range : 0.0f;
+				float soft = 1.0f + range * atanf((bulge - 1.0f) * scale) / (0.5f * M_PI);
+				
+				bulge = interpf(soft, hard, data->bulge_smooth);
 			}
-			CLAMP_MAX(bulge, data->bulge_max);
-
-			bulge = interpf(bulge_smoothed, bulge, data->bulge_smooth);
 		}
-		else if (data->flag & STRETCHTOCON_USE_BULGE_MIN) {
-			/* The quadratic formula below creates a smooth asymptote
-			 * of the clamped bulge value. By scaling x with the inverse smooth factor
-			 * the smoothed area becomes smaller ("less smoothing").
-			 * For very small smoothing factor below epsilon it is replaced
-			 * by the clamped version to avoid floating point precision issues.
-			 */
-			const float epsilon = 0.000001f;
-			if (data->bulge_smooth < epsilon) {
-				CLAMP_MIN(bulge, data->bulge_min);
-			}
-			else {
-				float scale = data->bulge_smooth;
-				float inv_scale = 1.0f / scale;
-				float x = (bulge - data->bulge_min) * 0.5f * inv_scale;
-				bulge = scale * (x + sqrtf((x * x) + 1.0f)) + data->bulge_min;
+		if (bulge < 1.0f) {
+			if (data->flag & STRETCHTOCON_USE_BULGE_MIN) {
+				float bulge_min = CLAMPIS(data->bulge_max, 0.0f, 1.0f);
+				float hard = max_ff(bulge, bulge_min);
+				
+				float range = 1.0f - bulge_min;
+				float scale = (range > 0.0f) ? 1.0f / range : 0.0f;
+				float soft = 1.0f - range * atanf((1.0f - bulge) * scale) / (0.5f * M_PI);
+				
+				bulge = interpf(soft, hard, data->bulge_smooth);
 			}
 		}
 		
diff --git a/source/blender/blenloader/intern/versioning_270.c b/source/blender/blenloader/intern/versioning_270.c
index d8da0a12b50..bd1b5f2c269 100644
--- a/source/blender/blenloader/intern/versioning_270.c
+++ b/source/blender/blenloader/intern/versioning_270.c
@@ -114,6 +114,19 @@ static void do_version_constraints_radians_degrees_270_5(ListBase *lb)
 	}
 }
 
+static void do_version_constraints_stretch_to_limits(ListBase *lb)
+{
+	bConstraint *con;
+
+	for (con = lb->first; con; con = con->next) {
+		if (con->type == CONSTRAINT_TYPE_STRETCHTO) {
+			bStretchToConstraint *data = (bStretchToConstraint *)con->data;
+			data->bulge_min = 1.0f;
+			data->bulge_max = 1.0f;
+		}
+	}
+}
+
 void blo_do_versions_270(FileData *fd, Library *UNUSED(lib), Main *main)
 {
 	if (!MAIN_VERSION_ATLEAST(main, 270, 0)) {
@@ -405,4 +418,21 @@ void blo_do_versions_270(FileData *fd, Library *UNUSED(lib), Main *main)
 			image->gen_color[3] = 1.0f;
 		}
 	}
+
+	if (!DNA_struct_elem_find(fd->filesdna, "bStretchToConstraint", "float", "bulge_min")) {
+		Object *ob;
+
+		/* Update Transform constraint (again :|). */
+		for (ob = main->object.first; ob; ob = ob->id.next) {
+			do_version_constraints_stretch_to_limits(&ob->constraints);
+
+			if (ob->pose) {
+				/* Bones constraints! */
+				bPoseChannel *pchan;
+				for (pchan = ob->pose->chanbase.first; pchan; pchan = pchan->next) {
+					do_version_constraints_stretch_to_limits(&pchan->constraints);
+				}
+			}
+		}
+	}
 }
diff --git a/source/blender/makesrna/intern/rna_constraint.c b/source/blender/makesrna/intern/rna_constraint.c
index aab2d35c0e4..77355dbad0e 100644
--- a/source/blender/makesrna/intern/rna_constraint.c
+++ b/source/blender/makesrna/intern/rna_constraint.c
@@ -1377,12 +1377,12 @@ static void rna_def_constraint_stretch_to(BlenderRNA *brna)
 	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
 
 	prop = RNA_def_property(srna, "bulge_min", PROP_FLOAT, PROP_NONE);
-	RNA_def_property_range(prop, 0.0, 100.f);
+	RNA_def_property_range(prop, 0.0, 1.0f);
 	RNA_def_property_ui_text(prop, "Volume Variation Minimum", "Minimum volume stretching factor");
 	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
 
 	prop = RNA_def_property(srna, "bulge_max", PROP_FLOAT, PROP_NONE);
-	RNA_def_property_range(prop, 0.0, 100.f);
+	RNA_def_property_range(prop, 1.0, 100.0f);
 	RNA_def_property_ui_text(prop, "Volume Variation Maximum", "Maximum volume stretching factor");
 	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");