getScreenCullingShape

A convex polygon that describes the shape of the screen in case it is non-rectangular. Every screen-coordinate is in 0 to 1 range, with (0, 0) being top-left and (1, 1) bottom-right. The points have to be given in clockwise winding order. The polygon will be closed automatically, so for a rectangular shape, pass in 4 points. Use this if the visible screen area is obscured enough that using a custom shape improves performance.