add respect-prev-transform Configrc variable

panda/src/collide/collisionTraverser.cxx

@@ -41,7 +41,7 @@ PStatCollector CollisionTraverser::_collisions_pcollector("App:Collisions");
 ////////////////////////////////////////////////////////////////////
 CollisionTraverser::
 CollisionTraverser() {
-  _respect_prev_transform = false;
+  _respect_prev_transform = respect_prev_transform;
 #ifdef DO_COLLISION_RECORDING
   _recorder = (CollisionRecorder *)NULL;
 #endif

panda/src/collide/config_collide.cxx

@@ -43,6 +43,14 @@ ConfigureFn(config_collide) {
   init_libcollide();
 }
 
+// Set this true to have all CollisionTraversers in the world respect
+// the previous frame's transform (position) for a given object when
+// determining motion for collision tests.  If this is false, you must
+// explicitly enable motion detection for a particular traverser.  It
+// is false by default to force programmers to decide on a
+// case-by-case basis whether they really need this feature.
+const bool respect_prev_transform = config_collide.GetBool("respect-prev-transform", false);
+
 ////////////////////////////////////////////////////////////////////
 //     Function: init_libcollide
 //  Description: Initializes the library.  This must be called at

panda/src/collide/config_collide.h

@@ -24,6 +24,8 @@
 
 NotifyCategoryDecl(collide, EXPCL_PANDA, EXPTP_PANDA);
 
+extern const bool respect_prev_transform;
+
 extern EXPCL_PANDA void init_libcollide();
 
 #endif