Sunday, 20 November 2016

Animation Production Process 008

Arnold materials attributes using AiStandard

Absolutely loving using the Arnold renderer. Although it is still new and has some missing features, it is definitely my favourite for rendering currently. Though my experience with other renders is only very basic with Mental-Ray.

Covering more about material attributes. An aspect of rendering I always enjoy working with as it adds a whole new level of realism. Of course realism is not only limited to creating objects and characters from life, but it gives you the ability to realise fantasy worlds as well.

I could play around with rendering objects and different materials for hours. I really like being able to use a list of IOR's (Index of Refraction) of different materials to quickly create believable substances. I was initially confused at using different IOR values for objects touching each other but after some thought I realised why. using glass at 1.5 and glass at 1.33, I'd assume 0.8 is to bring the IOR from 1.5 to 1.33. 1.5 * 0.8 = 1.2, which is close enough to water, of course you could adjust the values accordingly. This also demonstrates that the IOR stacks multiplicative.

It is difficult to experiments with these rendering effects. I may assign myself an exercise that uses the various types of maps, specular, bump, diffuse etc. to either create a real world object or as a demonstration on a flat plane object. I can also apply the materials to objects and scenes in other Maya projects accordingly.

What I found curious about some of the IOR lists was the fact that opaque materials also had IOR values. I was curious as to why, I initially thought of it as "If light passed through this...". I soon found that the IOR has an influence on reflective materials and how light is reflected. What I found interesting about this is the polarisation of light through reflection. Something I have come across previously, but never fully understood. In simplified terms, I will likely remember it as a change in light frequency that requires an equal frequency to pick it up again. Doesn't seem majorly useful for digital 3D but interesting nonetheless.

Further Experimentation

Looking at the IORs I saw diamond, so I thought I might experiment. I brought up a picture of a diamond for reference and started experimenting.


Result of using a cone primitive and applying simple AiStandard settings with 2.418 IOR. Looking back at the reference, there's a lot more light being reflected and refracted.

Not quite there yet. Going to remodel into something more diamond shape. Also looking into the Solid Angle support pages. Definitely learning a lot more about Arnold with each new experiment. Creating a diamond is much more difficult than expected, I may have to look into this later. most resources I could find were using Mental Ray. May have to see if the same process works for Arnold.

Did some changes to the mesh and added a spotlight. Brought out the shapes a little better. Getting closer but definitely need to do more research.

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