[Bf-blender-cvs] [e1ae95f6b2a] master: Fix T93520: wrong subframe motion blur with rigid body physics

[Brecht Van Lommel]

Commit: e1ae95f6b2a3106c008e94b11cda9ba3e6d59ae3
Author: Brecht Van Lommel
Date:   Thu Jan 20 20:28:56 2022 +0100
Branches: master
https://developer.blender.org/rBe1ae95f6b2a3106c008e94b11cda9ba3e6d59ae3

Fix T93520: wrong subframe motion blur with rigid body physics

The code here was using velocity based interpolation copied from particles.
However there is no velocity cached in the rigid body point cache so the
results were non-sensical.

===================================================================

M	source/blender/blenkernel/intern/pointcache.c

===================================================================

diff --git a/source/blender/blenkernel/intern/pointcache.c b/source/blender/blenkernel/intern/pointcache.c
index 38575f3048f..602546db8df 100644
--- a/source/blender/blenkernel/intern/pointcache.c
+++ b/source/blender/blenkernel/intern/pointcache.c
@@ -831,31 +831,23 @@ static void ptcache_rigidbody_interpolate(int index,
     RigidBodyOb *rbo = ob->rigidbody_object;
 
     if (rbo->type == RBO_TYPE_ACTIVE) {
-      ParticleKey keys[4];
-      ParticleKey result;
-      float dfra;
-
-      memset(keys, 0, sizeof(keys));
-
-      copy_v3_v3(keys[1].co, rbo->pos);
-      copy_qt_qt(keys[1].rot, rbo->orn);
+      /* It may be possible to improve results by taking into account velocity
+       * for interpolation using psys_interpolate_particle, however this is
+       * not currently cached. */
+      float pos[3], orn[4];
 
       if (old_data) {
-        memcpy(keys[2].co, data, sizeof(float[3]));
-        memcpy(keys[2].rot, data + 3, sizeof(float[4]));
+        memcpy(pos, data, sizeof(float[3]));
+        memcpy(orn, data + 3, sizeof(float[4]));
       }
       else {
-        BKE_ptcache_make_particle_key(&keys[2], 0, data, cfra2);
+        PTCACHE_DATA_TO(data, BPHYS_DATA_LOCATION, index, pos);
+        PTCACHE_DATA_TO(data, BPHYS_DATA_ROTATION, index, orn);
       }
 
-      dfra = cfra2 - cfra1;
-
-      /* NOTE: keys[0] and keys[3] unused for type < 1 (crappy). */
-      psys_interpolate_particle(-1, keys, (cfra - cfra1) / dfra, &result, true);
-      interp_qt_qtqt(result.rot, keys[1].rot, keys[2].rot, (cfra - cfra1) / dfra);
-
-      copy_v3_v3(rbo->pos, result.co);
-      copy_qt_qt(rbo->orn, result.rot);
+      const float t = (cfra - cfra1) / (cfra2 - cfra1);
+      interp_v3_v3v3(rbo->pos, rbo->pos, pos, t);
+      interp_qt_qtqt(rbo->orn, rbo->orn, orn, t);
     }
   }
 }