New particle collisions code:

* The old collisions code detected particle collisions by calculating the
  collision times analytically from the collision mesh faces. This was
  pretty accurate, but didn't support rotating/deforming faces at all, as
  the equations for these quickly become quite nasty.
* The new code uses a simple "distance to plane/edge/vert" function and
  iterates this with the Newton-Rhapson method to find the closest particle
  distance during a simulation step.
* The advantage in this is that the collision object can now move, rotate,
  scale or even deform freely and collisions are still detected reliably.
* For some extreme movements the calculation errors could stack up so much
  that the detection fails, but this can be easily fixed by increasing the
  particle size or simulation substeps.
* As a side note the algorithm doesn't really do point particles anymore,
  but uses a very small radius as the particle size when "size deflect" isn't
  selected.
* I've also updated the collision response code a bit, so now the particles
  shouldn't leak even from tight corners.

All in all the collisions code is now much cleaner and more robust than before!

1 files changed, 9 insertions, 8 deletions

diff --git a/source/blender/modifiers/intern/MOD_collision.c b/source/blender/modifiers/intern/MOD_collision.c
index 2ed66f2374b..83ba8a12163 100644
--- a/source/blender/modifiers/intern/MOD_collision.c
+++ b/source/blender/modifiers/intern/MOD_collision.c
@@ -64,7 +64,7 @@ static void initData(ModifierData *md)
 	collmd->current_x = NULL;
 	collmd->current_xnew = NULL;
 	collmd->current_v = NULL;
-	collmd->time = -1000;
+	collmd->time_x = collmd->time_xnew = -1000;
 	collmd->numverts = 0;
 	collmd->bvhtree = NULL;
 }
@@ -95,7 +95,7 @@ static void freeData(ModifierData *md)
 		collmd->current_x = NULL;
 		collmd->current_xnew = NULL;
 		collmd->current_v = NULL;
-		collmd->time = -1000;
+		collmd->time_x = collmd->time_xnew = -1000;
 		collmd->numverts = 0;
 		collmd->bvhtree = NULL;
 		collmd->mfaces = NULL;
@@ -139,11 +139,11 @@ static void deformVerts(ModifierData *md, Object *ob,
 		current_time = BKE_curframe(md->scene);
 		
 		if(G.rt > 0)
-			printf("current_time %f, collmd->time %f\n", current_time, collmd->time);
+			printf("current_time %f, collmd->time_xnew %f\n", current_time, collmd->time_xnew);
 		
 		numverts = dm->getNumVerts ( dm );
 		
-		if((current_time > collmd->time)|| (BKE_ptcache_get_continue_physics()))
+		if((current_time > collmd->time_xnew)|| (BKE_ptcache_get_continue_physics()))
 		{
 			unsigned int i;
 
@@ -151,7 +151,7 @@ static void deformVerts(ModifierData *md, Object *ob,
 			if(collmd->x && (numverts != collmd->numverts))
 				freeData((ModifierData *)collmd);
 			
-			if(collmd->time == -1000) // first time
+			if(collmd->time_xnew == -1000) // first time
 			{
 				collmd->x = dm->dupVertArray(dm); // frame start position
 				
@@ -174,7 +174,7 @@ static void deformVerts(ModifierData *md, Object *ob,
 				// create bounding box hierarchy
 				collmd->bvhtree = bvhtree_build_from_mvert(collmd->mfaces, collmd->numfaces, collmd->x, numverts, ob->pd->pdef_sboft);
 				
-				collmd->time = current_time;
+				collmd->time_x = collmd->time_xnew = current_time;
 			}
 			else if(numverts == collmd->numverts)
 			{
@@ -182,6 +182,7 @@ static void deformVerts(ModifierData *md, Object *ob,
 				tempVert = collmd->x;
 				collmd->x = collmd->xnew;
 				collmd->xnew = tempVert;
+				collmd->time_x = collmd->time_xnew;
 				
 				memcpy(collmd->xnew, dm->getVertArray(dm), numverts*sizeof(MVert));
 				
@@ -216,7 +217,7 @@ static void deformVerts(ModifierData *md, Object *ob,
 					bvhtree_update_from_mvert ( collmd->bvhtree, collmd->mfaces, collmd->numfaces, collmd->current_x, collmd->current_xnew, collmd->numverts, 1 );
 				}
 				
-				collmd->time = current_time;
+				collmd->time_xnew = current_time;
 			}
 			else if(numverts != collmd->numverts)
 			{
@@ -224,7 +225,7 @@ static void deformVerts(ModifierData *md, Object *ob,
 			}
 			
 		}
-		else if(current_time < collmd->time)
+		else if(current_time < collmd->time_xnew)
 		{	
 			freeData((ModifierData *)collmd);
 		}