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, 2 insertions, 0 deletions

diff --git a/source/blender/makesdna/DNA_cloth_types.h b/source/blender/makesdna/DNA_cloth_types.h
index 6c7d500e4e2..a9e066ef45e 100644
--- a/source/blender/makesdna/DNA_cloth_types.h
+++ b/source/blender/makesdna/DNA_cloth_types.h
@@ -69,6 +69,8 @@ typedef struct ClothSimSettings {
 	float	goalspring;
 	float	goalfrict;
 	float	velocity_smooth; /* smoothing of velocities for hair */
+	float	pressure;			/* pressure factor from hair density */
+	float	pressure_threshold;	/* minimum density for hair pressure */
 	float	collider_friction; /* friction with colliders */
 	float	vel_damping; /* damp the velocity to speed up getting to the resting position */
 	float	shrink_min;  /* min amount to shrink cloth by 0.0f (no shrink) - 1.0f (shrink to nothing) */