Update multi-return sampling parameters to (3,19) (#299)

Author: prybicki

src/gpu/MultiReturn.hpp

@@ -16,8 +16,8 @@
 
 #include <RGLFields.hpp>
 
-#define MULTI_RETURN_BEAM_VERTICES 8
-#define MULTI_RETURN_BEAM_LAYERS 2
+#define MULTI_RETURN_BEAM_VERTICES 19
+#define MULTI_RETURN_BEAM_LAYERS 3
 #define MULTI_RETURN_BEAM_SAMPLES (1 + (MULTI_RETURN_BEAM_VERTICES * MULTI_RETURN_BEAM_LAYERS))
 
 struct MultiReturnPointers