Add box-into-plane collision test

panda/src/collide/collisionBox.I

@@ -130,6 +130,16 @@ get_center() const {
   return _center;
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: CollisionBox::get_dimensions
+//       Access: Published
+//  Description:
+////////////////////////////////////////////////////////////////////
+INLINE LVector3 CollisionBox::
+get_dimensions() const {
+  return _max - _min;
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: CollisionBox::get_radius
 //       Access: Published

panda/src/collide/collisionBox.h

@@ -68,6 +68,7 @@ PUBLISHED:
   INLINE void set_center(const LPoint3 &center);
   INLINE void set_center(PN_stdfloat x, PN_stdfloat y, PN_stdfloat z);
   INLINE const LPoint3 &get_center() const;
+  INLINE LVector3 get_dimensions() const;
   INLINE PN_stdfloat get_radius() const;
 
 protected:

panda/src/collide/collisionPlane.cxx

@@ -390,6 +390,51 @@ test_intersection_from_parabola(const CollisionEntry &entry) const {
   return new_entry;
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: CollisionPlane::test_intersection_from_box
+//       Access: Public, Virtual
+//  Description: This is part of the double-dispatch implementation of
+//               test_intersection().  It is called when the "from"
+//               object is a box.
+////////////////////////////////////////////////////////////////////
+PT(CollisionEntry) CollisionPlane::
+test_intersection_from_box(const CollisionEntry &entry) const {
+  const CollisionBox *box;
+  DCAST_INTO_R(box, entry.get_from(), 0);
+
+  const LMatrix4 &wrt_mat = entry.get_wrt_mat();
+
+  LPoint3 from_center = box->get_center() * wrt_mat;
+  LVector3 from_extents = box->get_dimensions() * wrt_mat * 0.5;
+  PN_stdfloat dist = _plane.dist_to_plane(from_center);
+
+  LVecBase3 box_x = entry.get_wrt_mat().get_row3(0);
+  LVecBase3 box_y = entry.get_wrt_mat().get_row3(1);
+  LVecBase3 box_z = entry.get_wrt_mat().get_row3(2);
+
+  if (abs(dist) >
+      abs(box_x.dot(_plane.get_normal()) * from_extents[0]) +
+      abs(box_y.dot(_plane.get_normal()) * from_extents[1]) +
+      abs(box_z.dot(_plane.get_normal()) * from_extents[2])) {
+    // No collision.
+    return NULL;
+  }
+
+  if (collide_cat.is_debug()) {
+    collide_cat.debug()
+      << "intersection detected from " << entry.get_from_node_path()
+      << " into " << entry.get_into_node_path() << "\n";
+  }
+  PT(CollisionEntry) new_entry = new CollisionEntry(entry);
+
+  LVector3 normal = (has_effective_normal() && box->get_respect_effective_normal()) ? get_effective_normal() : get_normal();
+
+  new_entry->set_surface_normal(normal);
+  new_entry->set_surface_point(from_center - get_normal() * dist);
+
+  return new_entry;
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: CollisionPlane::fill_viz_geom
 //       Access: Protected, Virtual

panda/src/collide/collisionPlane.h

@@ -71,6 +71,8 @@ protected:
   test_intersection_from_segment(const CollisionEntry &entry) const;
   virtual PT(CollisionEntry)
   test_intersection_from_parabola(const CollisionEntry &entry) const;
+  virtual PT(CollisionEntry)
+  test_intersection_from_box(const CollisionEntry &entry) const;
 
   virtual void fill_viz_geom();