Falloff node - Simple HOWTO

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Falloff node - Simple HOWTO

Postby FooZe » Tue Sep 11, 2012 4:00 am

This is a really basic howto for the new falloff node that is now available in 2.59 beta and upwards.
It's mainly designed for those who perhaps have never met falloff before...

What is it?
The falloff map is a floattexture that is shaded dependent on the viewing angle to the material (or rather geometry that the material is on).

falloffBasic.jpg


What is it used for?
Anywhere you want to have a material that reacts differently depending on viewing angle. Mainly usefull for fabric and architectural glass. Connect the falloff node to the amount input of a mix material to control the blend of the two.

Where can i find it?
The falloff map is found under textures:

addNode.png
addNode.png (26.43 KiB) Viewed 32748 times


Settings:

falloff-controlls.jpg


There are 3 parameters for the falloff node.
I will give functional explanations of the 3 parameters rather than technical details...
1) normal – this effects the color of the surface at direct on viewing anges. 0 = black, 1 = white.
2) Grazing – this effects the color of the surface at shallower viewing angles. 1= white, 0 = black
3) falloff index – this effects the blending of the above two values.


Here is an example of cloth with (left) and without (right) the use of falloff:
falloffComparison.jpg


Here is a test i did somewhat simulating the crazy car paint from the 90's:
crazycarpaint.jpg


And probably the most useful but more subtle usage is architectural glass:
(Glossy material with full reflection and falloff to control the opacity)
With falloff (notice the reduced reflection on the windows that are pointing more towards the camera)
falloffGlass.jpg


Without falloff (0.3 opacity regardless of viewing angle):
(Notice the slightly unrealistically high reflection on the lower windows and through the almost face on window on the 2nd floor)
point3opacityglass-nofalloff2.jpg


Here are the settings to create this glass.
It is a glossy material with full specular, minimum roughness and a falloff node connected to the opacity input.
Setting the falloff index to around 2.9 is a good starting point but it's a good idea to tweak this depending on your scene.
falloffGlasssSettings.jpg
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Re: Falloff node - Simple HOWTO

Postby nildoe » Tue Sep 11, 2012 9:29 am

Thx alot for this small but VERY useful tutorial Fooze

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Re: Falloff node - Simple HOWTO

Postby kavorka » Tue Sep 11, 2012 12:34 pm

Simple, basic, but much needed :)
thanks for the explanation. The only time I have ever used falloff before, was to get that cool look of microbs and really small things viewed under a microscope.

The falloff node definetly helps out that glass, gotta start using this :)
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Re: Falloff node - Simple HOWTO

Postby merid888 » Mon Oct 01, 2012 12:05 pm

hi thank you for this tutorial, but you don't say how creat the material and values, is important setting of materials, can you be more especific to help as ? maybe a few pictures step by step to create a realistic glass ?
thank you
regards :)
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Re: Falloff node - Simple HOWTO

Postby FooZe » Mon Oct 01, 2012 9:38 pm

Hi merid888,

Sorry for the lack of info. I have added a screenshot of the setting needed.
Let me know if you need anything else.

Cheers
Chris.
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Re: Falloff node - Simple HOWTO

Postby Tugpsx » Tue Oct 02, 2012 1:03 am

Wow very nice. Wonder if this would look good with SubSurface Scatter. This could make an interesting effect for human skin.
Thanks for sharing.
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Re: Falloff node - Simple HOWTO

Postby andw » Fri Oct 05, 2012 10:25 am

Very interested in cloth example with falloff. What node of (diffuse?) material should I connect falloff node output to get same effect?
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Re: Falloff node - Simple HOWTO

Postby FooZe » Sun Oct 07, 2012 8:31 pm

Hi andw,

Use a mix material and then use the falloff node for the mix amount.
Something like this:
falloff-mix.jpg


With that you can control exactly what both the straight on and grazing parts will look like.

Cheers
Chris.
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Re: Falloff node - Simple HOWTO

Postby niuq.cam » Sat Oct 20, 2012 11:12 pm

Why do you say : using a glossy material and not a specular material for architectural glass ?
Thx.
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Re: Falloff node - Simple HOWTO

Postby FooZe » Tue Oct 23, 2012 3:00 am

Hi Niuq.cam,

There are a couple of reasons why i used a glossy material as opposed to a specular...
1) It is easy, only one plane is required and you don't need to worry about index of refraction changing your view of the room.
2) Using the opacity means that some rays will go directly through the window as if it were not there therefore you get better lighting on the inside of the room.
3) If you use the falloff node to control the opacity of a specular material with an index of refraction this will cause problems as there will be two "views" through the glass: 1) the un-refracted rays that have gone straight through due to the opacity being less than 1 and 2) the refracted rays that have gone through the specular material.

(I have thought of an played with two specular planes (both front and back of the window) and using the falloff node to control the reflection parameter, but this doesn't really provide much benefit and increases the complexity. Also this will cause you to run into problems with lighting objects behind the glass with the sunlight environment).

Cheers
Chris.
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