FunctionDelegate3
fun <RT : GenType, F : Func<RT>, P1 : Variable, P2 : Variable, P3 : Variable> FunctionDelegate3(funcType: (GlslGenerator) -> F, param1: (GlslGenerator) -> P1, param2: (GlslGenerator) -> P2, param3: (GlslGenerator) -> P3, body: (P1, P2, P3) -> RT)