CGTalk - Is refractive index the same as real life?

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brianemsu2

08-16-2003, 10:40 PM

Hi,
I am experiencing some strange phenomena with the refractive index setting in Maya.

I have your basic glass bottle that has a low diffuse settting and a high transparency setting. Ray-tracing is turned on to get the refractions.
To get the refractions to look anywhere close to real, I have to turn the refractive index down to around 0.9 or so.
I thought this was kind of weird seeing how real glass has a ref. index of around 1.5.
When I turn the ref. index up that high in maya, the light refracts as if the bottle is solid glass and not hollow.
Has anyone experienced this?
I appreciate any help!

LocoMan

08-17-2003, 03:03 AM

I'm not sure if it's this way in Maya, but I've read that in several apps the refraction works one way (the way polygon's normals are facing), while in real life the light would do into the glass, out of the class, then into the glass again and out of the glass again. IIRC from high school psychics, there is one index from when the light leaves the air and enters the glass, and when it leaves the glass to enter the air.

The workaround was to have two copies of the model, one of them with the normals inverted, and then apply the glass to air refraction to one and the air to glass to the other one.

Again, not sure if that applies to Maya, never used it other than some quick playing with the hotbox in the 4.5 PLE.

brianemsu2

08-17-2003, 05:33 PM

I think I have it set up right with the normals facing all in the right direction. The bottle is made from a curve that continues from the bottom outside of the bottle all the way to the top and over and inside to the bottom of the bottle...the normals are all facing out on the outside of the bottle and then face inwards on the inside. It is just not refracting light right.
Please run that fix by me again... You have to make an inverse of the geometry or something?

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