Cloth: Componentize forces

This separates cloth stiffness and damping forces into tension,
compression, and shearing components, allowing more control over the
cloth behaviour.

This also adds a bending model selector (although the new bending model
itself is not implemented in this commit). This is because some of the
features implemented here only make sense within the new bending model,
while the old model is kept for compatibility.

This commit makes non-breaking changes, and thus maintains full
compatibility with existing simulations.

Reviewed By: brecht

Differential Revision: http://developer.blender.org/D3655

3 files changed, 22 insertions, 6 deletions

diff --git a/source/blender/blenkernel/BKE_cloth.h b/source/blender/blenkernel/BKE_cloth.h
index 82a8d7f4e43..a099ae46d78 100644
--- a/source/blender/blenkernel/BKE_cloth.h
+++ b/source/blender/blenkernel/BKE_cloth.h
@@ -167,11 +167,17 @@ typedef enum {
 	CLOTH_SIMSETTINGS_FLAG_TEARING = ( 1 << 4 ),// true if tearing is enabled
 	CLOTH_SIMSETTINGS_FLAG_SCALING = ( 1 << 8 ), /* is advanced scaling active? */
 	CLOTH_SIMSETTINGS_FLAG_CCACHE_EDIT = (1 << 12),	/* edit cache in editmode */
-	CLOTH_SIMSETTINGS_FLAG_NO_SPRING_COMPRESS = (1 << 13), /* don't allow spring compression */
+	CLOTH_SIMSETTINGS_FLAG_RESIST_SPRING_COMPRESS = (1 << 13), /* don't allow spring compression */
 	CLOTH_SIMSETTINGS_FLAG_SEW = (1 << 14), /* pull ends of loose edges together */
 	CLOTH_SIMSETTINGS_FLAG_DYNAMIC_BASEMESH = (1 << 15), /* make simulation respect deformations in the base object */
 } CLOTH_SIMSETTINGS_FLAGS;
 
+/* ClothSimSettings.bending_model. */
+typedef enum {
+	CLOTH_BENDING_LINEAR	= 0,
+	CLOTH_BENDING_ANGULAR	= 1,
+} CLOTH_BENDING_MODEL;
+
 /* COLLISION FLAGS */
 typedef enum {
 	CLOTH_COLLSETTINGS_FLAG_ENABLED = ( 1 << 1 ), /* enables cloth - object collisions */
diff --git a/source/blender/blenkernel/intern/cloth.c b/source/blender/blenkernel/intern/cloth.c
index caf5b94b30e..54236785509 100644
--- a/source/blender/blenkernel/intern/cloth.c
+++ b/source/blender/blenkernel/intern/cloth.c
@@ -85,13 +85,18 @@ void cloth_init(ClothModifierData *clmd )
 	clmd->sim_parms->gravity[0] = 0.0;
 	clmd->sim_parms->gravity[1] = 0.0;
 	clmd->sim_parms->gravity[2] = -9.81;
-	clmd->sim_parms->structural = 15.0;
-	clmd->sim_parms->max_struct = 15.0;
-	clmd->sim_parms->shear = 15.0;
+	clmd->sim_parms->tension = 15.0;
+	clmd->sim_parms->max_tension = 15.0;
+	clmd->sim_parms->compression = 15.0;
+	clmd->sim_parms->max_compression = 15.0;
+	clmd->sim_parms->shear = 5.0;
+	clmd->sim_parms->max_shear = 5.0;
 	clmd->sim_parms->bending = 0.5;
 	clmd->sim_parms->max_bend = 0.5;
+	clmd->sim_parms->tension_damp = 5.0;
+	clmd->sim_parms->compression_damp = 5.0;
+	clmd->sim_parms->shear_damp = 5.0;
 	clmd->sim_parms->bending_damping = 0.5;
-	clmd->sim_parms->Cdis = 5.0;
 	clmd->sim_parms->Cvi = 1.0;
 	clmd->sim_parms->mass = 0.3f;
 	clmd->sim_parms->stepsPerFrame = 5;
@@ -134,6 +139,8 @@ void cloth_init(ClothModifierData *clmd )
 
 	clmd->sim_parms->voxel_cell_size = 0.1f;
 
+	clmd->sim_parms->bending_model = CLOTH_BENDING_ANGULAR;
+
 	if (!clmd->sim_parms->effector_weights)
 		clmd->sim_parms->effector_weights = BKE_add_effector_weights(NULL);
 
@@ -728,6 +735,9 @@ static void cloth_apply_vgroup ( ClothModifierData *clmd, Mesh *mesh )
 					if (clmd->sim_parms->flags & CLOTH_SIMSETTINGS_FLAG_SCALING ) {
 						if ( dvert->dw[j].def_nr == (clmd->sim_parms->vgroup_struct-1)) {
 							verts->struct_stiff = dvert->dw [j].weight;
+						}
+
+						if ( dvert->dw[j].def_nr == (clmd->sim_parms->vgroup_shear-1)) {
 							verts->shear_stiff = dvert->dw [j].weight;
 						}
 
diff --git a/source/blender/blenkernel/intern/particle_system.c b/source/blender/blenkernel/intern/particle_system.c
index de4d25a95d9..a5ce7893d3e 100644
--- a/source/blender/blenkernel/intern/particle_system.c
+++ b/source/blender/blenkernel/intern/particle_system.c
@@ -3171,7 +3171,7 @@ static void do_hair_dynamics(ParticleSimulationData *sim)
 		psys->clmd = (ClothModifierData*)modifier_new(eModifierType_Cloth);
 		psys->clmd->sim_parms->goalspring = 0.0f;
 		psys->clmd->sim_parms->vel_damping = 1.0f;
-		psys->clmd->sim_parms->flags |= CLOTH_SIMSETTINGS_FLAG_GOAL|CLOTH_SIMSETTINGS_FLAG_NO_SPRING_COMPRESS;
+		psys->clmd->sim_parms->flags |= CLOTH_SIMSETTINGS_FLAG_GOAL|CLOTH_SIMSETTINGS_FLAG_RESIST_SPRING_COMPRESS;
 		psys->clmd->coll_parms->flags &= ~CLOTH_COLLSETTINGS_FLAG_SELF;
 	}