Fix T71620: broken particle collisions due to rB0666ece2e2f9

An optimisation in the collision system for cloth (static collisions),
broke the particle collisions, as they take motion into account. This
restores the moving BVH required for the particle collisions, while
keeping the optimisation for the cloth collisions.

Reviewed By: mano-wii

Maniphest Tasks: T71620

Differential Revision: https://developer.blender.org/D6560

2 files changed, 26 insertions, 17 deletions

diff --git a/source/blender/blenkernel/BKE_collision.h b/source/blender/blenkernel/BKE_collision.h
index 5d7a5094eb5..5bf697e5df9 100644
--- a/source/blender/blenkernel/BKE_collision.h
+++ b/source/blender/blenkernel/BKE_collision.h
@@ -125,7 +125,10 @@ void bvhtree_update_from_mvert(BVHTree *bvhtree,
 
 // move Collision modifier object inter-frame with step = [0,1]
 // defined in collisions.c
-void collision_move_object(struct CollisionModifierData *collmd, float step, float prevstep);
+void collision_move_object(struct CollisionModifierData *collmd,
+                           const float step,
+                           const float prevstep,
+                           const bool moving_bvh);
 
 void collision_get_collider_velocity(float vel_old[3],
                                      float vel_new[3],
diff --git a/source/blender/blenkernel/intern/collision.c b/source/blender/blenkernel/intern/collision.c
index 91d66e16dde..220b9417a6c 100644
--- a/source/blender/blenkernel/intern/collision.c
+++ b/source/blender/blenkernel/intern/collision.c
@@ -77,9 +77,11 @@ typedef struct SelfColDetectData {
  ***********************************/
 
 /* step is limited from 0 (frame start position) to 1 (frame end position) */
-void collision_move_object(CollisionModifierData *collmd, float step, float prevstep)
+void collision_move_object(CollisionModifierData *collmd,
+                           const float step,
+                           const float prevstep,
+                           const bool moving_bvh)
 {
-  float oldx[3];
   unsigned int i = 0;
 
   /* the collider doesn't move this frame */
@@ -92,13 +94,17 @@ void collision_move_object(CollisionModifierData *collmd, float step, float prev
   }
 
   for (i = 0; i < collmd->mvert_num; i++) {
-    interp_v3_v3v3(oldx, collmd->x[i].co, collmd->xnew[i].co, prevstep);
-    interp_v3_v3v3(collmd->current_x[i].co, collmd->x[i].co, collmd->xnew[i].co, step);
-    sub_v3_v3v3(collmd->current_v[i].co, collmd->current_x[i].co, oldx);
+    interp_v3_v3v3(collmd->current_x[i].co, collmd->x[i].co, collmd->xnew[i].co, prevstep);
+    interp_v3_v3v3(collmd->current_xnew[i].co, collmd->x[i].co, collmd->xnew[i].co, step);
+    sub_v3_v3v3(collmd->current_v[i].co, collmd->current_xnew[i].co, collmd->current_x[i].co);
   }
 
-  bvhtree_update_from_mvert(
-      collmd->bvhtree, collmd->current_x, NULL, collmd->tri, collmd->tri_num, false);
+  bvhtree_update_from_mvert(collmd->bvhtree,
+                            collmd->current_xnew,
+                            collmd->current_x,
+                            collmd->tri,
+                            collmd->tri_num,
+                            moving_bvh);
 }
 
 BVHTree *bvhtree_build_from_mvert(const MVert *mvert,
@@ -513,9 +519,9 @@ static int cloth_collision_response_static(ClothModifierData *clmd,
                                   &w3);
 
     collision_compute_barycentric(collpair->pb,
-                                  collmd->current_x[collpair->bp1].co,
-                                  collmd->current_x[collpair->bp2].co,
-                                  collmd->current_x[collpair->bp3].co,
+                                  collmd->current_xnew[collpair->bp1].co,
+                                  collmd->current_xnew[collpair->bp2].co,
+                                  collmd->current_xnew[collpair->bp3].co,
                                   &u1,
                                   &u2,
                                   &u3);
@@ -872,9 +878,9 @@ static void cloth_collision(void *__restrict userdata,
   distance = compute_collision_point(verts1[tri_a->tri[0]].tx,
                                      verts1[tri_a->tri[1]].tx,
                                      verts1[tri_a->tri[2]].tx,
-                                     collmd->current_x[tri_b->tri[0]].co,
-                                     collmd->current_x[tri_b->tri[1]].co,
-                                     collmd->current_x[tri_b->tri[2]].co,
+                                     collmd->current_xnew[tri_b->tri[0]].co,
+                                     collmd->current_xnew[tri_b->tri[1]].co,
+                                     collmd->current_xnew[tri_b->tri[2]].co,
                                      data->culling,
                                      data->use_normal,
                                      pa,
@@ -1117,7 +1123,7 @@ ListBase *BKE_collider_cache_create(Depsgraph *depsgraph, Object *self, Collecti
       col->ob = ob;
       col->collmd = cmd;
       /* make sure collider is properly set up */
-      collision_move_object(cmd, 1.0, 0.0);
+      collision_move_object(cmd, 1.0, 0.0, true);
       BLI_addtail(cache, col);
     }
   }
@@ -1319,7 +1325,7 @@ int cloth_bvh_collision(
         }
 
         /* Move object to position (step) in time. */
-        collision_move_object(collmd, step + dt, step);
+        collision_move_object(collmd, step + dt, step, false);
 
         overlap_obj[i] = BLI_bvhtree_overlap(
             cloth_bvh, collmd->bvhtree, &coll_counts_obj[i], NULL, NULL);
@@ -1664,7 +1670,7 @@ void cloth_find_point_contacts(Depsgraph *depsgraph,
     }
 
     /* move object to position (step) in time */
-    collision_move_object(collmd, step + dt, step);
+    collision_move_object(collmd, step + dt, step, true);
   }
 
   collider_contacts = MEM_callocN(sizeof(ColliderContacts) * numcollobj, "CollPair");