Unity用GL库画线

真机调试时，有时候需要在屏幕中快速添加一些调试信息，如人物的碰撞盒， 准星范围等，可用gl在屏幕上画矩形圆形等来显示：

开始绘制：

void Begin (Color color)
{
    if (s_material == null)
        s_material = new Material (Shader.Find ("Unlit/Color"));
        s_material.SetPass (0);
        GL.LoadOrtho ();
        GL.Begin (GL.LINES);
        s_material.SetColor ("_Color", color);
}

结束绘制：

void End ()
{
    GL.End ();
}

绘制矩形：

public void DrawScreenRect(Rect rect, Color color)
{
    Begin (color);

    GL.Vertex3 (rect.xMin / Screen.width, rect.yMin / Screen.height, 0);
    GL.Vertex3 (rect.xMin / Screen.width, rect.yMax / Screen.height, 0);

    GL.Vertex3 (rect.xMin / Screen.width, rect.yMax / Screen.height, 0);
    GL.Vertex3 (rect.xMax / Screen.width, rect.yMax / Screen.height, 0);

    GL.Vertex3 (rect.xMax / Screen.width, rect.yMax / Screen.height, 0);
    GL.Vertex3 (rect.xMax / Screen.width, rect.yMin / Screen.height, 0);

    GL.Vertex3 (rect.xMax / Screen.width, rect.yMin / Screen.height, 0);
    GL.Vertex3 (rect.xMin / Screen.width, rect.yMin / Screen.height, 0);

    End ();
}

绘制椭圆：

public void DrawScreenEllipse(Vector2 center, float xRadius, float yRadius, Color color, int smooth = 50)
{
    Begin (color);
    for (int i = 0; i < smooth; ++i)
    {
        int nextStep = (i + 1) % smooth;
        GL.Vertex3 ((center.x + xRadius * Mathf.Cos (2 * Mathf.PI / smooth * i)) / Screen.width,
        (center.y + yRadius * Mathf.Sin (2 * Mathf.PI / smooth * i)) / Screen.height, 0);
        GL.Vertex3 ((center.x + xRadius * Mathf.Cos (2 * Mathf.PI / smooth * nextStep)) / Screen.width,
        (center.y + yRadius * Mathf.Sin (2 * Mathf.PI / smooth * nextStep)) / Screen.height, 0);
    }

    End ();
}