glass reflection issue ?

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yponomos
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Post by yponomos » Thu Jul 20, 2006 8:14 pm

probably the fresnel effect...

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OnoSendai
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Post by OnoSendai » Thu Jul 20, 2006 8:25 pm

That is quite odd... perhaps a normal smoothing, or normal reversal issue?

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OnoSendai
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Post by OnoSendai » Thu Jul 20, 2006 9:03 pm

ok i'll check it out

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OnoSendai
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Post by OnoSendai » Sat Jul 22, 2006 3:09 am

radiance wrote:i forgot to mention that when setting the IOR very high, eg 5.0+
it seems to go away... eg everything is reflective.
but then again it does'nt look ok anymore due to the glass being a mirror everywhere instead of propper glass...

greetz,
radiance
This is correct, at high IOR, a dielectric becomes very reflective at all angles.

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OnoSendai
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Post by OnoSendai » Sat Jul 22, 2006 4:29 am

Ok.. spent a little bit of time debugging this issue.
As far as I can tell, it's due to some windows having normals facing the wrong way. The entry and exit IORs were switched, and total internal reflection was causing the reflected fraction to be 1.0, as opposed to something like 0.1 which it should be.

So for glass, the normals *have* to be facing the right way (outwards), on both sides of the pane of glass.

btw, in the top image, the green circled windows have the correct amount of reflection I think.

8bstudio
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Post by 8bstudio » Thu Sep 28, 2006 10:49 pm

Hi all!!!
A question: for glass window and to have a right reflections, can we use a plane with normal out or it's obligatory use a cube object with normals out?

Thanks!

debris
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Post by debris » Fri Sep 29, 2006 12:01 am

I guess you'll have to use a cube for a window. Otherwise it would look like the whole house was filled with glass, because the lightrays never get "out" of the glass again.

8bstudio
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Post by 8bstudio » Fri Sep 29, 2006 12:07 am

Thank you Debris,
now I understand because my windows doesn't reflect anything also with IOR >2.0.
:D :D :D

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