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Re: Decal on glass object,.

Posted: Thu Dec 03, 2009 6:29 pm
by JDHill
No problem...step by step:
1. make your glass material
2. revolve your bottle profile
3. assign the material
Nothing special going on here.
4. extract the bottle's inner shell
That's so we can map the two pieces separately...
5. set the outer shell to use cylindrical mapping
Also, nothing special here.
6. set the inner shell to use planar mapping (projected from above)
7. stretch the planar mapping such that the decal portion falls outside the object
Basically, I am saying that since you have to use one material on one mesh in order to have the dielectric render correctly, we need to have a way to make sure that the decal is not mapped onto any visible portion of the inside of the bottle. So we planar map it, and resize the mapping plane such that the decal is not showing up on the innner shell of the bottle. Here, I've mapped it onto a plane to show how the UVs for the inner shell are ending up:

Image
8. use Mesh > From NURBS Object to make two meshes
9. hide or delete the NURBS bottle
10. run Join on the two meshes
We are counting on the fact that the UVs of the two meshes will not be modified when we run Join - we will then have a bottle which is a single closed mesh, and whose UVs are such that the decal is only visible on the outer shell, where we positioned it using a cylindrical mapping.

Does that help explain it?

Re: Decal on glass object,.

Posted: Thu Dec 03, 2009 8:28 pm
by caryjames
Thanks JD- I think that does explain it..the process was completely different from anything that I have done using Rhino/Maxwell so it stumped me a little. I will have to try this out for myself after Christmas and experiment a bit. The part that was getting me was using the same material for the inside of the bottle as well as the outside.. clever bit moving the mapping to hide the decal for the inside but not the outside! I definitely would not have gone about the problem in this way so big thanks for taking the time to outline the process!
Cary

Re: Decal on glass object,.

Posted: Mon Dec 07, 2009 11:58 am
by kami
that's an interesting approach ...
i got one question to understand the problem:
would it not work if you'd have a second glass material without the decal and would apply it to the inner shell without joining these two meshes?

Re: Decal on glass object,.

Posted: Mon Dec 07, 2009 4:04 pm
by bjorn.syse
Pretty cool JD!

Re: Decal on glass object,.

Posted: Mon Dec 07, 2009 6:42 pm
by JDHill
Kami - no, it wouldn't work. Maxwell needs you to supply it with a physically-accurate object if you want it to figure refraction correctly. In another app with support for sub-object materials, it would be possible to assign a second glass material to the inside of the bottle, but the bottle would still need to be one mesh in the MXS.