Reflection Falloff

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Reflection Falloff

Postby valerostudio » Wed Jan 18, 2012 7:08 pm

Does anyone understand the FallOff settings in order to achieve this

ReflectionBlur.jpg
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Re: Reflection Falloff

Postby andybot » Wed Jan 18, 2012 8:31 pm

create a new material in the vray editor "angle blend" (right click on scene materials) and pick your two colors. The start angle should be 90 and stop angle is 200 (looking at an example one I have.)
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Re: Reflection Falloff

Postby andybot » Wed Jan 18, 2012 8:54 pm

Here is a test image. The material is one I got from a car paint material, I updated it to a red material (labeled "<dark gray>") and a gray material (labeled "sw 2860 sage") (BTW, to explain the random nature of the model, I blew the roof off since the lighting was getting messed up with an interior view.)
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Re: Reflection Falloff

Postby valerostudio » Wed Jan 18, 2012 10:50 pm

What I am looking to do is have the reflection falloff. Like the effect you would get on a finished floor.

cubeRender.jpg
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Re: Reflection Falloff

Postby andybot » Wed Jan 18, 2012 10:54 pm

Oops! You're talking about the floor material :oops:
There's a falloff texture you can use in the reflection slot.

edit: hmm, but it would need to be in the reflection slot. Anyhow, isn't that what the fresnel effect does anyway? You could maybe play with the parallel and perpendicular color?
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Re: Reflection Falloff

Postby oganocali » Wed Jan 18, 2012 11:41 pm

Indeed fresnel map for reflective layer reduces reflection strength for more obtuse rays. The increase in fuzziness can be obtained by reducing the glossiness of the reflective layer. This is obtained with glossiness 0.85 and fresnel map with index 5. This does not fit your first case exactly (this one somehow has a smoother feel) but you may find it useful.

good luck
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Re: Reflection Falloff

Postby nomeradona » Thu Jan 19, 2012 2:47 am

oganocoli was right just use fresnel refelction and blurrying it
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Re: Reflection Falloff

Postby andybot » Thu Jan 19, 2012 3:54 am

The first image is definitely just a blurry reflection. Like oganocali says - using .85 for glossiness would work fine. The second one has an accentuated falloff without the blurriness. I wonder if it's just a lower IOR value, like 1.2
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Re: Reflection Falloff

Postby oganocali » Thu Jan 19, 2012 1:16 pm

I have trouble replication the graduated fall off effect in picture 2. In theory fresnel reflection should do it for small ior. Somehow vray fresnel reflection falls off too abruptly as in total internal reflection as seen (ior 1.2). I am pretty sure I have the correct surface orientation but... Apparently vray is doing some kind of approximation for this reflection. I am pretty sure the physics require a smooth graduated fall off. Strange.
fresnelonly.jpg
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Re: Reflection Falloff

Postby andybot » Thu Jan 19, 2012 1:26 pm

do you have a filter color for the reflection layer? I see that effect sometimes if the filter color is too dark. Set it at white and see if you still get that effect.
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Re: Reflection Falloff

Postby thomthom » Thu Jan 19, 2012 1:37 pm

oganocali: remember that you also need to make the reflection blurry in order to reproduce the original image posted.
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Re: Reflection Falloff

Postby oganocali » Thu Jan 19, 2012 1:51 pm

@andybot: I don't have a filter.
@thomthom: I was trying to reproduce the effect in the 2nd picture. I feel that one does not have blurriness.

Well, just before the reflection drops to zero there is a small graduated region I think, may be I am imagining it.
There seems to be something I am missing.
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Re: Reflection Falloff

Postby valerostudio » Thu Jan 19, 2012 3:11 pm

Wow, I must be dense! I dont know why I didn't realize Fresnel did this. I have used it a million times. What what you use if you wanted it to fade off in a shorter distance? Would you just change the IOR value?
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Re: Reflection Falloff

Postby oganocali » Thu Jan 19, 2012 3:49 pm

@valerostudio: Smaller value of IOR should make the reflection fade off earlier as I understand , but somehow in vray the reflection dies off more completely and abruptly than I expect.
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Re: Reflection Falloff

Postby thomthom » Thu Jan 19, 2012 4:03 pm

I did use falloff once for such an effect in 3dsmax. Found it, then, easier to control in that situation than fresnel.
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Re: Reflection Falloff

Postby valerostudio » Thu Jan 19, 2012 8:02 pm

But we all agree that fresnel is the best solution for realistic reflections? Would you ever just use a color value to control the reflection amount and not use fresnel?
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Re: Reflection Falloff

Postby thomthom » Fri Jan 20, 2012 10:59 am

valerostudio wrote:But we all agree that fresnel is the best solution for realistic reflections?

Yes
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