Reflection glossiness as fcurve?

[rray]

Hi,
I'd like to control reflection glossiness by an fcurve, not just by 1 parameter. Does a shader (preferably mental ray) like this exist?

As an example, I'm looking for a shader that could create a mix of a high gloss reflection with a low gloss reflection using an fcurve that has a peak at 0 and another peak at 1. This for all kinds of fcurves of course.

Wondered for some time if something like this existed. I think this would be useful for quite a few metallic looking shaders like bronze, brass etc. Has anyone ever heard of something like that? Hope I was able to make myself clear. Maybe is this what BRDF (sp?) is??

Cheers xD

edit: of course adding all these reflections would make evrything pretty bright. The result would have to be normalized in some way

[Mathaeus]

so what's input for this function curve. If you mean angle between camera ray and surface normal (incidence or whatever), I think old t2s Illumination had option for variable glossiness, relative to 'incidence'. Seems to be "in" for path tracers to have some variation too, let's say Beckmann specular model for glossy path-traced reflection in Blender Cycles - but I'm not sure does it apply to glossiness, or it's just color multiplier.

Forget me if I missed the point.

[rray]

There would be no input, all values would be used, similar to painting a spectrum to get a color, or pipe organ sliders to get a sound. Just basically mixing a lot different glossiness values.

[Fer]

you can control it with whatever gray scale 0-1 mapping you want, just note that glossy reflection in mia material are somehow exponential not linear, it start the make a difference between low and high glossy at 0.5,
where 0.001 => 0 is where you get all the strong diffuse glossy, so a change range node or a scalar curve is your best bet.

[gustavoeb]

how come, no input? what would the fcurve be modulating then?

[rray]

It's similar to having 12 or so sliders to control the addition of 12 different glossiness values. But I would think an fcurve would be a nicer interface for this.

@Fer : this would be only one value for each sample, but I'd be looking for multiple values for each sample (like a spectrum)

[gustavoeb]

so basic you want something like a audio equalizer, but for glossiness... intersting.
it seems hard to get what you want through the way things are exposed in the render tree :/

the basic idea would be to sample many inputs along a curve... each sample should be at:
current input/total of inputs

so for example if you have 12 inputs, the 6 input (6/12) would be at 0.5.

at any rate you would need to share this curve along many different scalar curve nodes, but not like the ICEtree, the actual curve is not exposed in the RenderTree :/
so my solution is no good...

[rray]

Oh yes curve profile would be nice to have exposed for building rt-compounds . . . Although I can't think of too many other uses right now :o)

Writing a custom shader would work for this but I'm having doubts if it would be worth the effort for the gained performance, compared to just using a mix of 8 architecturals and exposing a lot of sliders in a equalizer kind of way.
Thanks for the replies!