Drawing a fresnel falloff / ramp?

# 1 10-04-2008 , 01:35 PM

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If anyone has used 3ds Max, you know that a fresnel falloff can be drawn by playing with bezier points on an actual 0-1 curve.

In maya I have been piping a spot info node (facing ratio) into a ramp...and the ramp then dictates the fresnel falloff. My question is - is there a way in maya to make this curve with beziers rather than with a ramp more like a falloff in max? I like to make my own fresnel falloffs and it makes more sense to me to be able to actually see the curve in profile and weight it with beziers rather than using a ramp...

-John

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# 2 14-04-2008 , 02:09 AM

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why dont you use the fresnel shader?

dumb question i know..

everything starts and ends in the right place at the right time.

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# 3 16-04-2008 , 01:04 AM

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Because when art directing the fresnel on, say, car paint - one needs to be able to have complete control over the incidence angle falloff. Although the default fresnel is a "mathematical" fresnel, our research shows that many car paints have a curve that is MUCH steeper and more weighted. By drawing a curve in profile it is much easier to get that photoreal look and tweak it to match reference.

I found a script that will tie the frensel to points in the graph editor to draw it there...but unfortunately it isn't supported by our renderer of choice user added image

-John

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# 4 16-04-2008 , 04:55 AM

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I understand. this makes sense ofc.

I thought about a workaround. if it is only for visualization purpose to get a feeling for the curve you could try this ->

open Hypergraph - crate a hightField from the maya general utilities. take a simple ramp texture make it black and white and map the texture into the heightField´s Displacement channel. increase the heightField´s Resolution untill you get a smooth curve. I also set the ramp Interpolation to smooth, but you can play with the settings. you should pretty fast end up with something like this. see pics.

now you can tweak the ramp till your heart´s content. the hightField in viewport shows a direct representation of your b/w rampTexture. it´s no bezier curve I know, but it helps to get a better feeling of the ramp texture.

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