Tag Archives: fresnel

Fresnel Schlick’s approximation in Maya

fresnel_schlick_approximation

So recently I had the need to convert some Arnold materials to Vray. The aiStandard uses the Schlick’s approximation under the “reflectance at normal” attribute, similar to the Mental ray’s brdf control, the difference is that in Arnold you only have control over the 0 degree reflection, not 90 degrees slider or brdf curve control like in the Mia material. But, VrayMtl doesn’t have any other control for reflection falloff other than based on IOR, so having the background on the Fresnel formula implementation with remapValue node and sampler info, the Schlick’s approximation should be easy enough to implement and attach to a VrayMtl. In this post I am going to share with you the Schlick approximation formula in python and how to get around some issues.

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Custom Fresnel curves in Maya – Part 2

custom_fresnel_maya_python_part2

This is a follow up post from the first part on how to create custom fresnel curves in maya. In this second part I will break down the script that was added to the custom tools that you can download from creativecrash. This gives you the chance to create your own version and perhaps learn some python scripting.

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Custom Fresnel curves in Maya

custom_fresnel_curves_maya

So, we all know about fresnel reflections, objects reflect more at grazing angles. A few years ago we would use the facing ratio and a ramp to achieve that effect, and then reverse the result in the diffuse to keep somehow a physical based workflow. With more recent shaders and render engines we can drive the reflection with the index of refraction (ior or n) which works great for dielectric materials (plastic, wood, etc) but for metals the index of refraction is a bit more complex and very few render engines have gone through the trouble of writing those more complex reflection formulas. The question is: does it make any difference at all? Can’t we just tweek it until “looks good”? Sure we can, after all it’s all about art, making it look good, and realism is not always pleasing. So don’t take this too serious, but in the end you might learn something.

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