New FAQ section on rendering and materials

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New FAQ section on rendering and materials

Postby joepal » Tue Jun 06, 2017 2:39 pm

I've started a new section in the FAQ (http://www.makehumancommunity.org/wiki/ ... ode_setups) on rendering and materials. So far I've only added a piece on how to add glitter to the eyes.

If you have good node setups or similar for improving materials and rendering for aspects of MH toons (skins, hair whatnot), then please add new sections here. That way they'll be easier to find than when stored in forum threads.

Everyone should be able to edit the FAQ wiki page. To add a new FAQ entry, edit the main FAQ page and add the section (just copy, paste and change another line). Then save and click the new entry to create a new empty page.
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Re: New FAQ section on rendering and materials

Postby blindsaypatten » Tue Jun 06, 2017 5:36 pm

Your FAQ section uses an Add shader where I think it should use a Mix shader. My understanding is that the shaders reflect light that is scattered diffusely, light that is reflected coherently (specular reflection like a mirror) from a smooth glossy surface, and light that is refracted and transmitted through a transparent material. The mix shader uses the factor to determine how much of each of the three occurs, dividing the incoming light the three ways. An Add shader would have the same light reflecting and refracting, creating more light out than is coming in. This could be used for effect but won't be consistent with the actual physics.

Here's the general case:
GeneralShader.png

The value node is just there to show that the roughness factor that determines whether light reflects coherently or diffusely is a single physical property of the material and should have the same value in the two nodes. The key point here is that light will either refract through the transparent surface OR reflect off of it, so the more you reflect off with the glossy node the less makes it through to the eyeball below, so a high gloss will produce a dim grey eye underneath. So if you want both gloss and a white eye the solution is to crank up the light rather than crank up the gloss.


For they eye, we can simplify the exterior surface to only reflecting and refracting light, simplifying the nodes to:
SurfaceShader.png

TooGlossy.png
The eye on the right has a high gloss setting so little light makes it to the underlying surface
TooGlossy.png (39.62 KiB) Viewed 1996 times

LowerGloss.png
With a factor of 0.1
LowerGloss.png (38.96 KiB) Viewed 1996 times

Fresnel.png
Using a Fresnel node for the gloss versus transmit factor. Light that hits at small angles is more likely to reflect than refract.
Fresnel.png (40.68 KiB) Viewed 1996 times


For the inner surface if we ignore reflection and refraction just model diffuse reflection the nodes for the inner surface are simplified to:
EyeballShader.png


Let's see if someone corrects me before altering the FAQ.
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Re: New FAQ section on rendering and materials

Postby joepal » Tue Jun 06, 2017 10:25 pm

This was intended. I did not choose the add shader because of not understanding what a mix shader does.

I am aware that the add shader is not physically correct. The point was to provide an easy way to add a glitter effect while avoiding dimming the underlying eye white. Since the problem is generally that there is too little light reaching the eye white, not that too much reaches it, my thinking is that an add shader is appropriate in this case.
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Re: New FAQ section on rendering and materials

Postby RobBaer » Tue Jun 06, 2017 11:48 pm

"glitter" --> "shine" or better "watery shine" ??

so says my US English ear drum ? :D
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Re: New FAQ section on rendering and materials

Postby blindsaypatten » Wed Jun 07, 2017 2:54 am

joepal wrote:This was intended. I did not choose the add shader because of not understanding what a mix shader does.

I am aware that the add shader is not physically correct. The point was to provide an easy way to add a glitter effect while avoiding dimming the underlying eye white. Since the problem is generally that there is too little light reaching the eye white, not that too much reaches it, my thinking is that an add shader is appropriate in this case.


Sorry, I didn't write that all out because I thought you didn't know, I wrote it out in detail to solidify it in my own mind, along with leaving something behind for other people like myself that are relatively new to this. That said, it does seem to me that it is generally better to add a catch light and a mix node for a physically correct result than to achieve the effect with an Add node, so I would at least mention that approach. Of course there is nothing wrong with using the Add node for artistic reasons.

It's really too bad that none of the export formats can correctly transfer a glossy material to Blender, it's not like no one ever uses glossy materials. I guess MHX2 does if one tweaks the roughness to use the shininess value, but even then there is only one material for both the outer surface and the inner surface so you get incorrect reflections from the inner surface.
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