Glass/Plastic closed object properties

[stevesideas]

Hi Guys,

Im creating shaders for a car for a project im working on.

I need to know. If I have a car headlight lens and apply a plastic material to it, does it need to have thickness for the light to refract correctly? Im assuming that it does as if i dont, the renderer assumes that any object behind is encased in the plastic/glass and not just a thin surface over the top. Almost acting like a stone in a resin..if that makes sense.

Also, does the lens object have to be a closed mesh/poly object or can I have open vertices? The reason im asking is because the files have come from cad and are not completely sound in terms of closed meshes.

Thanks in advance

[Dynedain]

Yes you are right, the object should have a thickness with an inner surface, otherwise you'll get the cast effect.

It should be ok if your object isn't a watertight closed mesh, but you could end up with strange flickers or overbright spots if it's not.