When creating a physics system in GameMaker, it is often important to have a visual representation of what is actually happening with an instance. This can be achieved by using physics_draw_debug(), which draws a schematic outline of the physical properties associated with the instance running the code. Here is an image of how it looks:
It should be noted that for this to work it must be in the draw event of the instance, and it will be drawn using the currently defined draw colour.
physics_draw_debug()
N/A
draw_set_colour(c_red);
physics_draw_debug();
The code above will draw a representation of the physical properties associated with that instance using the colour red.