sample.fs

    let inline drawQuadTexture (x0, y0, u0, v0, c0) (x1, y1, u1, v1, c1) (x2, y2, u2, v2, c2) (x3, y3, u3, v3, c3) add vbo =
        vbo |> add x0 y0 u0 v0 c0
        vbo |> add x1 y1 u1 v1 c1
        vbo |> add x3 y3 u3 v3 c3

        vbo |> add x1 y1 u1 v1 c1
        vbo |> add x2 y2 u2 v2 c2
        vbo |> add x3 y3 u3 v3 c3
        
    let inline calcArc cx cy rx ry thickness start delta count f =         
        let inc = delta/float32 (count - 1)
        let mutable x = cos start
        let mutable y = sin start
        let c = cos inc
        let s = sin inc
        let mutable t = 0.f

        let r1 = rx
        let r2 = rx + thickness

        let mutable ax = 0.f
        let mutable ay = 0.f
        let mutable bx = 0.f
        let mutable by = 0.f

        for i = 0 to count-1 do
            let ax' = r2 * x + cx
            let ay' = r2 * y + cy
            let bx' = r1 * x + cx
            let by' = r1 * y + cy
            f (ax, ay, bx, by) (ax', ay', bx', by')
            ax <- ax'
            bx <- bx'
            ay <- ay'
            by <- by'
            t <- x
            x <- c * x - s * y
            y <- s * t + c * y