Preparation for collision code fixing.

Instead of handling contact tests and collision response in the same
function in collision.c, first generate contact points and return them
as a list, then free at the end of the stepping function. This way the
contact response can be integrated into the conjugate gradient method
properly instead of using the hackish and unstable double evaluation
that is currently used.

1 files changed, 132 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/collision.c b/source/blender/blenkernel/intern/collision.c
index 2c0939359e0..427b76ab778 100644
--- a/source/blender/blenkernel/intern/collision.c
+++ b/source/blender/blenkernel/intern/collision.c
@@ -1364,3 +1364,135 @@ int cloth_points_objcollision(Object *ob, ClothModifierData *clmd, float step, f
 
 	return 1|MIN2 ( ret, 1 );
 }
+
+void cloth_find_point_contacts(Object *ob, ClothModifierData *clmd, float step, float dt,
+                               ColliderContacts **r_collider_contacts, int *r_totcolliders)
+{
+	Cloth *cloth= clmd->clothObject;
+	BVHTree *cloth_bvh;
+	unsigned int i=0, numverts = 0;
+	ClothVertex *verts = NULL;
+	
+	ColliderContacts *collider_contacts;
+	
+	Object **collobjs = NULL;
+	unsigned int numcollobj = 0;
+	
+	verts = cloth->verts;
+	numverts = cloth->numverts;
+	
+	////////////////////////////////////////////////////////////
+	// static collisions
+	////////////////////////////////////////////////////////////
+	
+	// create temporary cloth points bvh
+	cloth_bvh = BLI_bvhtree_new(numverts, MAX2(clmd->coll_parms->epsilon, clmd->coll_parms->distance_repel), 4, 6);
+	/* fill tree */
+	for (i = 0; i < numverts; i++) {
+		float co[6];
+		
+		copy_v3_v3(&co[0*3], verts[i].x);
+		copy_v3_v3(&co[1*3], verts[i].tx);
+		
+		BLI_bvhtree_insert(cloth_bvh, i, co, 2);
+	}
+	/* balance tree */
+	BLI_bvhtree_balance(cloth_bvh);
+	
+	collobjs = get_collisionobjects(clmd->scene, ob, clmd->coll_parms->group, &numcollobj, eModifierType_Collision);
+	if (!collobjs) {
+		*r_collider_contacts = NULL;
+		*r_totcolliders = 0;
+		return;
+	}
+	
+	/* move object to position (step) in time */
+	for (i = 0; i < numcollobj; i++) {
+		Object *collob= collobjs[i];
+		CollisionModifierData *collmd = (CollisionModifierData *)modifiers_findByType(collob, eModifierType_Collision);
+		if (!collmd->bvhtree)
+			continue;
+		
+		/* move object to position (step) in time */
+		collision_move_object ( collmd, step + dt, step );
+	}
+	
+	collider_contacts = MEM_callocN(sizeof(ColliderContacts) * numcollobj, "CollPair");
+	
+	// check all collision objects
+	for (i = 0; i < numcollobj; i++) {
+		ColliderContacts *ct = collider_contacts + i;
+		Object *collob= collobjs[i];
+		CollisionModifierData *collmd = (CollisionModifierData *)modifiers_findByType(collob, eModifierType_Collision);
+		BVHTreeOverlap *overlap;
+		unsigned int result = 0;
+		float epsilon;
+		
+		ct->ob = collob;
+		ct->collmd = collmd;
+		ct->collisions = NULL;
+		ct->totcollisions = 0;
+		
+		if (!collmd->bvhtree)
+			continue;
+		
+		/* search for overlapping collision pairs */
+		overlap = BLI_bvhtree_overlap(cloth_bvh, collmd->bvhtree, &result);
+		epsilon = BLI_bvhtree_getepsilon(collmd->bvhtree);
+		
+		// go to next object if no overlap is there
+		if (result && overlap) {
+			CollPair *collisions_index;
+			
+			/* check if collisions really happen (costly near check) */
+			cloth_points_objcollisions_nearcheck(clmd, collmd, &ct->collisions, &collisions_index,
+			                                     result, overlap, epsilon, dt);
+			ct->totcollisions = (int)(collisions_index - ct->collisions);
+			
+			// resolve nearby collisions
+//			ret += cloth_points_objcollisions_resolve(clmd, collmd, collob->pd, collisions[i], collisions_index[i], dt);
+		}
+		
+		if (overlap)
+			MEM_freeN(overlap);
+	}
+	
+	if (collobjs)
+		MEM_freeN(collobjs);
+
+	BLI_bvhtree_free(cloth_bvh);
+	
+	////////////////////////////////////////////////////////////
+	// update positions
+	// this is needed for bvh_calc_DOP_hull_moving() [kdop.c]
+	////////////////////////////////////////////////////////////
+	
+	// verts come from clmd
+	for (i = 0; i < numverts; i++) {
+		if (clmd->sim_parms->flags & CLOTH_SIMSETTINGS_FLAG_GOAL) {
+			if (verts [i].flags & CLOTH_VERT_FLAG_PINNED) {
+				continue;
+			}
+		}
+		
+		VECADD(verts[i].tx, verts[i].txold, verts[i].tv);
+	}
+	////////////////////////////////////////////////////////////
+	
+	*r_collider_contacts = collider_contacts;
+	*r_totcolliders = numcollobj;
+}
+
+void cloth_free_contacts(ColliderContacts *collider_contacts, int totcolliders)
+{
+	if (collider_contacts) {
+		int i;
+		for (i = 0; i < totcolliders; ++i) {
+			ColliderContacts *ct = collider_contacts + i;
+			if (ct->collisions) {
+				MEM_freeN(ct->collisions);
+			}
+		}
+		MEM_freeN(collider_contacts);
+	}
+}