Falloff / Fresnel On Floors

[Sneaker]

I'm not claiming to be an expert, but fresnel is a special falloff from the point of view
depending on the surface angle you're looking at.
The gradient you can modify goes from same direction as your point of view to flat.
For car paint reflection this gradient is perfect from close to white to dark grey.
The edges get a more glossy reflecting material where the direct view is nat as reflective
and you can see the color.
In fact almost every material has some kind of fresnel effect.
I wished there was an option to render a fresnel pass just like the depth pass.
Could save a lot of time during render and enhance the options in post.

-Michael

[lllab]

very simpel,
the pysically effect you want is fresnel fro floors glas etc.

it mirrors stronger when the viewangle is low(far away p.e.), like water in a pond or a glas or the finsh of a wooden floor. use in in reflection with gry or colored shades...

cheers
stefan

[paulselhi]

Thanks..so i would really just treat a floor as i would glass but with no transparency And the freanel grad would be white to black ( or light grey to dark grey) left to right ?


How does the falloff work here, would you use falloff at all and if so how would you combine it with the fresnel shader ?

[bdjones]

How does the falloff work here, would you use falloff at all and if so how would you combine it with the fresnel shader ?

Falloff calculates the angle (or uses the angle) between a vector (Y by default) and the surface normal. Since a floor has a constant surface normal, Falloff gives the same color for the whole floor so it's not useful for what you are thinking about, it's more useful for 'snow on the flat bits and not on the steep bits' sorts of things.

[paulselhi]

But wouldn't a floor have a fresnel effect ? in fact doesn't every reflective object exhibit a fresnel effect to some degree ?

I mean if you look at a relective floor from top down birdseye view you will get a different reflection than looking at it from floor level across the floor ?

Or maybe it's just that after 12 pints when i go through both postitions in quick succession my brain is undergoing a severe fresnel effect

[bdjones]

But wouldn't a floor have a fresnel effect ? in fact doesn't every reflective object exhibit a fresnel effect to some degree ?

I mean if you look at a reflective floor from top down birds-eye view you will get a different reflection than looking at it from floor level across the floor ?

Yes, to both. Fresnel works by checking out the viewing angle compared to the surface normal, so fresnel (if applied) is present on a floor since the viewing angle increases at long distance and moves toward 0 as view goes to 'straight down' (at least with a usual sort of floor setup).

Falloff uses a constant vector compared to the surface normal and since the surface normal of a floor is the same for the whole floor you get the same 'color' (read reflectivity or whatever) for the whole floor.

What I usually do while trying to figure out what some channel material is going to do in reflect/transparency/alpha etc. is to try it out in the color channel to get a grip on what I should expect to see. Pop in a floor, make a material, put Fresnel in the color channel and make the Fresnel go from red to green (so you can't be fooled by lights) put it on the floor and render. Now make a second material with Falloff in the color channel (the default black/red/yellow is good here) and render that. ...My apologies if you've already done that...

Or maybe it's just that after 12 pints when i go through both positions in quick succession my brain is undergoing a severe fresnel effect

:-)

[raycerx]

Not sure if this was said but fresnel will not work on the 'floor object' since it doesn't have normals... Is that true? My guess is that you need a poly object so that the fresnel shader can 'see' the normals and do its thing...
good thread by the way, interesting.

[Jorge Arango]

These are part of some test I did last year on this subject. Note that the mixing mode inside the layers and in the result of the layers with the color (reflection channel) is different for some of the files:

http://www.jearango.com/fresnel/index.htm

The files (without bitmaps):




Jorge Arango

[Jorge Arango]

Double post

[JDP]

Not sure if this was said but fresnel will not work on the 'floor object' since it doesn't have normals... Is that true?

No, that is not true, fresnel will work on a floor object.


regards,
JDP

[paulselhi]

Thanks Jorge, i will pull these apart for inspiration ( said the biologist to the frog)

[AkaKico]

Nice examples Jorge!

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