When using a 3D programma, and especially using transparant materials, and index of refreaction is used. In Blender 3D, the open source 3D package, an Index of Refraction can be set up when using ray transparancy, and this is also possible in other 3D packages. To achieve a realistic result, knowing the right refraction indexes is very useful. We see an example of refraction in the image on the left, but what exactly is transparancy, and what Refraction indexes do common materials have?
What is Index of Refraction?
Glass is for example transparent. That means, in simple words, that you can look through it. More materials, like some transparent plastics and water have also this ability. But glass has more properties than that you can just look through it. One thing is that the light within glass is refracted. The visual effect of this depends on the shape and sort of glass. It also applies to water. Do you ever remember a situation where your feet were in the water, and they looked bigger and the place of your feet was distorted? Or a spoon in a tea glass? Right, this is because light is reflected!
If you want more in depth physical information on this subject, you can look in this article on wikipedia:
http://en.wikipedia.org/wiki/Refractive_index
Common refraction indexes
Air: 1.00
Water (ice): 1.31
Water (liquid): 1.33
Glass (General, there are tiny differences between different kinds of glass): 1.5-1.65
PET (Transparent Plastic): 1.57
Diamond: 2.4
I saw that all the work I had in mind is already done. There is a pretty good index, for 3D Artists, available here:
http://www.robinwood.com/Catalog/Technical/Gen3DTuts/Gen3DPages/RefractionIndexList.html
Setting up Index of Refraction in Blender
In the tutorial ‘Modelling and Rendering a Realistic Perfume Bottle’ is shown a material set up for glass. We’ll use that here again and look where we can put in the Index of Refraction. When we apply Ray Transparency in Blender we have the option to set up the Index of Refraction. It is very simple in Blender, it is just called IOR (Index Of Refraction) and you can adjust it by moving the slider or entering a value. As you can see in the example below a value of 1.50 is used, which is close to the value of glass.
