This function must be called when you have finished defining the
points of your primitive. If you do not call this function,
nothing will be drawn as this effectively tells
GameMaker: Studio that you have finished and that it can now
draw the defined primitive.
tex = background_get_texture(back);
draw_vertex_texture(0, 480, 0, 0);
draw_vertex_texture(640, 480, 1, 0);
draw_vertex_texture(640, 480, 1, 1);
draw_vertex_texture(0, 480, 0, 1);
The above code will draw a 4 vertex triangle strip textured with the texture held in the "tex" variable.