Simple hair children: Initial implementation of twist control

It allows to have children hair to be twisted around parent curve, which is
quite an essential feature when creating hair braids.

There are currently two controls:

- Number of turns around parent children.
- Influence curve, which allows to modify "twistness" along the strand.

1 files changed, 32 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_particle.c b/source/blender/makesrna/intern/rna_particle.c
index 9e52457d32a..e9bbc981a13 100644
--- a/source/blender/makesrna/intern/rna_particle.c
+++ b/source/blender/makesrna/intern/rna_particle.c
@@ -944,6 +944,19 @@ static void rna_ParticleSettings_use_roughness_curve_update(Main *bmain, Scene *
 	rna_Particle_redo_child(bmain, scene, ptr);
 }
 
+static void rna_ParticleSettings_use_twist_curve_update(Main *bmain, Scene *scene, PointerRNA *ptr)
+{
+	ParticleSettings *part = ptr->data;
+
+	if (part->child_flag & PART_CHILD_USE_TWIST_CURVE) {
+		if (!part->twistcurve) {
+			BKE_particlesettings_twist_curve_init(part);
+		}
+	}
+
+	rna_Particle_redo_child(bmain, scene, ptr);
+}
+
 static void rna_ParticleSystem_name_set(PointerRNA *ptr, const char *value)
 {
 	Object *ob = ptr->id.data;
@@ -3170,6 +3183,25 @@ static void rna_def_particle_settings(BlenderRNA *brna)
 	RNA_def_property_struct_type(prop, "FieldSettings");
 	RNA_def_property_pointer_funcs(prop, "rna_Particle_field2_get", NULL, NULL, NULL);
 	RNA_def_property_ui_text(prop, "Force Field 2", "");
+
+	/* twist */
+	prop = RNA_def_property(srna, "twist", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_range(prop, -100000.0f, 100000.0f);
+	RNA_def_property_ui_range(prop, -10.0f, 10.0f, 0.1, 3);
+	RNA_def_property_ui_text(prop, "Twist", "Number of turns around parent allong the strand");
+	RNA_def_property_update(prop, 0, "rna_Particle_redo_child");
+
+	prop = RNA_def_property(srna, "use_twist_curve", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "child_flag", PART_CHILD_USE_TWIST_CURVE);
+	RNA_def_property_ui_text(prop, "Use Twist Curve", "Use a curve to define twist");
+	RNA_def_property_update(prop, 0, "rna_ParticleSettings_use_twist_curve_update");
+
+	prop = RNA_def_property(srna, "twist_curve", PROP_POINTER, PROP_NONE);
+	RNA_def_property_pointer_sdna(prop, NULL, "twistcurve");
+	RNA_def_property_struct_type(prop, "CurveMapping");
+	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+	RNA_def_property_ui_text(prop, "Twist Curve", "Curve defining twist");
+	RNA_def_property_update(prop, 0, "rna_Particle_redo_child");
 }
 
 static void rna_def_particle_target(BlenderRNA *brna)