Справка Houdini на русском Nodes VOP nodes

Is Front Face VOP node

Returns true if the normal of the surface is forward facing, and false if it isn’t.

This operator returns true if the normal of the surface is forward facing, and false if it isn’t.

If I or N are not wired, the global variables by the same names will be used instead. Neither vector needs to be normalized.

See also

VOP nodes