    intended size of the point to be rasterized, in pixels. It may be written at any time
            during shader execution. If <code class="constant">GL_PROGRAM_POINT_SIZE</code> is enabled,
            <code class="varname">gl_PointSize</code> is used to determine the size of rasterized
            points, otherwise it is ignored by the rasterization stage.
        </p>
        <p>
            In the tessellation control language, the <code class="varname">gl_PerVertex</code> named block
            is 