Fresnel for shading

[glorybound]

I always have something as a reference when I create new artwork. I never rely on my thoughts alone as inspiration. My secret tip for readers of 3D World is that I always use Fresnel for shading.

From a blog post on 3D World. What exactly does it mean to use I always use Fresnel for shading?

[Pixelcon]

As in he always has fresnel reflections switched on for every material he creates.

[glorybound]

That's what I thought

As in he always has fresnel reflections switched on for every material he creates.

[Alan Iglesias]

After reading some of his blog, it would seem that Mr. Sanchez-Lana might understandably enough not have such a complete command of English.

For example:

3D World: What’s your favourite 3D package and why?
SMSL: Photoshop, because is the most powerful tool in the ArchViz field.

I'm sure he knows the difference between a 2D and 3D application, but maybe he didn't understand the question so well.

Based on that, it may be that by "shading" he meant "creating a shader with reflective properties". Since there are plenty of folks out there who do not understand the concept of surfaces with dielectric properties and their relationships to reflected light, it happens that the reflection's fresnel component of the shader is sometimes not utilized and maybe this is what he referring to.

Just my best guess...

-Alan

[joconnell]

Well to be fair, you see a lot of studios like MIR get out of 3d as fast as they can and do a lot of their main style work in photoshop.

[thablanch]

It is impossible you missed it..

http://www.youtube.com/watch?v=U9rgG2vPAvQ

http://vrayinfo.spreadshirt.com/

Everything has fresnel... ask Chris

[joconnell]

Metals don't

[instinct]

Metals don't

They would tho, if we were using the full general Fresnel Formula (instead the one simplified for dielectrics) where IOR is a complex number (with the imaginary part being light absorption if i am not mistaken).

[joconnell]

Yep - even at that though they aren't as convenient with each of the R, G and B components of the light having a different set of numbers. It's possible to do something similar in max which I'll get around to, but the slightly annoying thing is that we have to rely on tables of scanned materials which aren't all that extensive. Compound metals seem harder again where you can't just combine the results of the components and then average the results. You're right though, even if we had the two part mental ray BRDF approximation, it wouldn't be as accurate but it'd be better than what we have now.

[instinct]

Well there is the usual trade-off between physical accuracy and control/usability. Controlling a Wavelength dependent IOR expressed as a (theoretically infinite number of (?)) complex number(s) is not exactly straight forward i'd say. Having scans of real-world materials is fine until you need to change things for artistic reasons *shudder*

Regards,
Thorsten

[joconnell]

Yep - I've got a maxscript that'll make a gradient that you can map to facing ratios based on that wavelength data - as you say though it's not exactly artist friendly. It'd be brilliant if max gave maxscript access to output curves then at least we could make a pretty accurate curve but use the minimum number of bezier handles to allow for easy tweaking afterwards.

[instinct]

True. And that is not the only use i'd have for that darn control

[joconnell]

In some ways it'd be great if the likes of bercon gradient or some kind of vray colour correction map was included with the main vray build so you can be guaranteed that there's something done right, with full maxscript access and it's installed by default on any machine or render node.

[instinct]

In some ways it'd be great if the likes of bercon gradient or some kind of vray colour correction map was included with the main vray build so you can be guaranteed that there's something done right, with full maxscript access and it's installed by default on any machine or render node.

If this was uservoice or an issue tracker you'd have my voice hehe. I'll give you a +1 instead

Thorsten

[joconnell]

We've asked vlado about this seeing as the maths behind the built in colour correct map seem to make a total mess of colour values, fingers crossed he's feeling his usual overly generous self over the next few service packs