Implemented internal hair pressure to prevent hair from collapsing in

on itself.

This uses the same voxel structure as the hair smoothing algorithm.
A slightly different method was suggested in the original paper
(Volumetric Methods for Simulation and Rendering of Hair), but this is
based on directing hair based on a target density, which is another
way of implementing global goals. Our own approach is to define a
pressure threshold above which the hair is repelled in the density
gradient direction to simulate internal pressure from collisions.

1 files changed, 12 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_cloth.c b/source/blender/makesrna/intern/rna_cloth.c
index cecc39c8e15..9ab6791b5fa 100644
--- a/source/blender/makesrna/intern/rna_cloth.c
+++ b/source/blender/makesrna/intern/rna_cloth.c
@@ -325,6 +325,18 @@ static void rna_def_cloth_sim_settings(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Collider Friction", "");
 	RNA_def_property_update(prop, 0, "rna_cloth_update");
 
+	prop = RNA_def_property(srna, "pressure", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "pressure");
+	RNA_def_property_range(prop, 0.0f, 1000.0f);
+	RNA_def_property_ui_text(prop, "Internal Pressure", "Generate outward force based on hair density");
+	RNA_def_property_update(prop, 0, "rna_cloth_update");
+
+	prop = RNA_def_property(srna, "pressure_threshold", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "pressure_threshold");
+	RNA_def_property_range(prop, 0.0f, 1000.0f);
+	RNA_def_property_ui_text(prop, "Internal Pressure Threshold", "No pressure force is generated below this pressure value");
+	RNA_def_property_update(prop, 0, "rna_cloth_update");
+
 	/* mass */
 
 	prop = RNA_def_property(srna, "mass", PROP_FLOAT, PROP_NONE);