VARYING_SLOT_PNTC, /* FS only */
VARYING_SLOT_TESS_LEVEL_OUTER, /* Only appears as TCS output. */
VARYING_SLOT_TESS_LEVEL_INNER, /* Only appears as TCS output. */
VARYING_SLOT_PNTC, /* FS only */
VARYING_SLOT_TESS_LEVEL_OUTER, /* Only appears as TCS output. */
VARYING_SLOT_TESS_LEVEL_INNER, /* Only appears as TCS output. */