rect and rectv support efficient specification of rectangles as two corner points. Each rectangle command takes four arguments, organized either as two consecutive pairs of (x, y) coordinates, or as two pointers to arrays, each containing an (x, y) pair. The resulting rectangle is defined in the z = 0 plane.

rect (Vertex2 x1 y1) (Vertex2 x2, y2) is exactly equivalent to the following sequence:

    renderPrimitive Polygon $ do
        vertex (Vertex2 x1 y1)
        vertex (Vertex2 x2 y1)
        vertex (Vertex2 x2 y2)
        vertex (Vertex2 x1 y2)

Note that if the second vertex is above and to the right of the first vertex, the rectangle is constructed with a counterclockwise winding.