Hair collision: Use the S matrix for enforcing contact constraints.

This is a first test, the contacts are very explosive atm because they
basically pin hair vertices globally on collision, which leads to
stretching of the springs which is then suddenly released in the next
frame.

1 files changed, 38 insertions, 32 deletions

diff --git a/source/blender/blenkernel/intern/implicit.c b/source/blender/blenkernel/intern/implicit.c
index 2a50cde9e66..72b44ddffb2 100644
--- a/source/blender/blenkernel/intern/implicit.c
+++ b/source/blender/blenkernel/intern/implicit.c
@@ -593,29 +593,6 @@ typedef struct Implicit_Data  {
 	fmatrix3x3 *P, *Pinv;		/* pre-conditioning matrix */
 } Implicit_Data;
 
-/* Init constraint matrix */
-static void update_matrixS(ClothVertex *verts, int numverts, fmatrix3x3 *S)
-{
-	unsigned int pinned = 0;
-	int i = 0;
-
-	/* Clear matrix from old vertex constraints */
-	for (i = 0; i < S[0].vcount; i++)
-		S[i].c = S[i].r = 0;
-
-	/* Set new vertex constraints */
-	for (i = 0; i < numverts; i++) {
-		if (verts [i].flags & CLOTH_VERT_FLAG_PINNED) {
-			S[pinned].c = S[pinned].r = i;
-			pinned++;
-		}
-	}
-
-	// S is special and needs specific vcount and scount
-	S[0].vcount = pinned; 
-	S[0].scount = 0;
-}
-
 int implicit_init(Object *UNUSED(ob), ClothModifierData *clmd)
 {
 	unsigned int i = 0;
@@ -655,9 +632,6 @@ int implicit_init(Object *UNUSED(ob), ClothModifierData *clmd)
 	id->B = create_lfvector(cloth->numverts);
 	id->dV = create_lfvector(cloth->numverts);
 	id->z = create_lfvector(cloth->numverts);
-	
-	id->S[0].vcount = 0;
-	update_matrixS(verts, cloth->numverts, id->S);
 
 	for (i = 0; i < cloth->numverts; i++) {
 		id->A[i].r = id->A[i].c = id->dFdV[i].r = id->dFdV[i].c = id->dFdX[i].r = id->dFdX[i].c = id->P[i].c = id->P[i].r = id->Pinv[i].c = id->Pinv[i].r = id->bigI[i].c = id->bigI[i].r = id->M[i].r = id->M[i].c = i;
@@ -1700,6 +1674,39 @@ bool implicit_hair_volume_get_texture_data(Object *UNUSED(ob), ClothModifierData
 
 /* ================================ */
 
+/* Init constraint matrix */
+static void setup_constraint_matrix(ClothVertex *verts, int numverts, ColliderContacts *contacts, int totcolliders, fmatrix3x3 *S)
+{
+	int i, j;
+
+	/* Clear matrix from old vertex constraints */
+	for (i = 0; i < S[0].vcount; i++)
+		S[i].c = S[i].r = 0;
+
+	/* pinned vertex constraints */
+	for (i = 0; i < numverts; i++) {
+		S[i].c = S[i].r = i;
+		if (verts[i].flags & CLOTH_VERT_FLAG_PINNED)
+			zero_m3(S[i].m);
+		else
+			unit_m3(S[i].m);
+	}
+
+	for (i = 0; i < totcolliders; ++i) {
+		ColliderContacts *ct = &contacts[i];
+		for (j = 0; j < ct->totcollisions; ++j) {
+			CollPair *collpair = &ct->collisions[j];
+			int v = collpair->face1;
+			
+			/* pinned verts handled separately */
+			if (verts[v].flags & CLOTH_VERT_FLAG_PINNED)
+				continue;
+			
+			zero_m3(S[v].m);
+		}
+	}
+}
+
 static void cloth_calc_force(ClothModifierData *clmd, float UNUSED(frame), lfVector *lF, lfVector *lX, lfVector *lV, fmatrix3x3 *dFdV, fmatrix3x3 *dFdX, ListBase *effectors, float time, fmatrix3x3 *M)
 {
 	/* Collect forces and derivatives:  F, dFdX, dFdV */
@@ -1970,14 +1977,10 @@ int implicit_solver(Object *ob, float frame, ClothModifierData *clmd, ListBase *
 	Implicit_Data *id = cloth->implicit;
 	ColliderContacts *contacts = NULL;
 	int totcolliders = 0;
-
+	
 	BKE_sim_debug_data_clear_category(clmd->debug_data, "collision");
-
+	
 	if (clmd->sim_parms->flags & CLOTH_SIMSETTINGS_FLAG_GOAL) { /* do goal stuff */
-		
-		/* Update vertex constraints for pinned vertices */
-		update_matrixS(verts, cloth->numverts, id->S);
-
 		for (i = 0; i < numverts; i++) {
 			// update velocities with constrained velocities from pinned verts
 			if (verts [i].flags & CLOTH_VERT_FLAG_PINNED) {
@@ -2000,6 +2003,9 @@ int implicit_solver(Object *ob, float frame, ClothModifierData *clmd, ListBase *
 		}
 	}
 	
+	/* setup vertex constraints for pinned vertices and contacts */
+	setup_constraint_matrix(verts, cloth->numverts, contacts, totcolliders, id->S);
+	
 	while (step < tf) {
 		// damping velocity for artistic reasons
 		mul_lfvectorS(id->V, id->V, clmd->sim_parms->vel_damping, numverts);