Fix cast_motion sometimes failing

- Fixes Godot physics failing when the cast Shape is inside of, or
already colliding with another Shape.
- Fixes Bullet physics failing when there is no motion.
- Ensures Godot and Bullet physics behave the same.
- Updates the documentation to exclude the caveats for the failures and
differences.

2 files changed, 4 insertions, 4 deletions

diff --git a/servers/physics_2d/space_2d_sw.cpp b/servers/physics_2d/space_2d_sw.cpp
index edadcabe0b..fdf6dd7a2a 100644
--- a/servers/physics_2d/space_2d_sw.cpp
+++ b/servers/physics_2d/space_2d_sw.cpp
@@ -278,9 +278,9 @@ bool PhysicsDirectSpaceState2DSW::cast_motion(const RID &p_shape, const Transfor
 			continue;
 		}
 
-		//test initial overlap
+		//test initial overlap, ignore objects it's inside of.
 		if (CollisionSolver2DSW::solve(shape, p_xform, Vector2(), col_obj->get_shape(shape_idx), col_obj_xform, Vector2(), nullptr, nullptr, nullptr, p_margin)) {
-			return false;
+			continue;
 		}
 
 		//just do kinematic solving
diff --git a/servers/physics_3d/space_3d_sw.cpp b/servers/physics_3d/space_3d_sw.cpp
index d9170cd986..337fbefed4 100644
--- a/servers/physics_3d/space_3d_sw.cpp
+++ b/servers/physics_3d/space_3d_sw.cpp
@@ -274,11 +274,11 @@ bool PhysicsDirectSpaceState3DSW::cast_motion(const RID &p_shape, const Transfor
 			continue;
 		}
 
-		//test initial overlap
+		//test initial overlap, ignore objects it's inside of.
 		sep_axis = p_motion.normalized();
 
 		if (!CollisionSolver3DSW::solve_distance(shape, p_xform, col_obj->get_shape(shape_idx), col_obj_xform, point_A, point_B, aabb, &sep_axis)) {
-			return false;
+			continue;
 		}
 
 		//just do kinematic solving