[Half Life]

I've been reading for quite some time and I have a question about coatings:

Why is "additive mode" used instead of "coatings" for things like plastics and wood floors when clearly in the real world coatings are used?

It seems to me coatings is the more logical and accurate model -- what am I missing?

Best,
Jason.

[tom]

You're, right. Except the coatings can't have roughness.

[Half Life]

Thanks for reply Tom!

Cool, I definitely get the value of that -- do real world coatings have roughness? I could see the value of SSS coatings for things like semi-gloss and matte coatings... Thin SSS maybe?

Best,
Jason.

[tom]

do real world coatings have roughness?

In real world, there's no such analytical roughness. It's all about displacement, a real micro-perturbance on the surface. Not only coatings but every surface is made of specular microsurfaces. BSDF's roughness parameter is a special approach simulating this and yet it's not compatible with the coating approach.

I could see the value of SSS coatings for things like semi-gloss and matte coatings... Thin SSS maybe?

An example image?

[Half Life]

When I use coatings I can use a fine (high rez) bump map to create "roughness" because the texture of the BSDF is inherited by the coating... is this not good enough?

I'm thinking matte and semi-gloss varnish -- used for paintings and sometimes picture frames... but that is subtle stuff I doubt a scanner would pick it up well enough to see the translucence. For that matter thin gel mediums with a minimum of pigment fits this description pretty well (used for glazing -- often used in faux finish painting). Certain types of pigment based furniture varnish and wood floor finishes would also fit this description... particles suspended in a transparent medium and applied thinly.

However as I say it would take the naked eye to really see it -- sort of like the iridescence varnished wood grain sometimes has as you tilt it... nearly impossible to see with anything but the naked eye but a very real part of the charm of wood. It's a very "rich" look... but I can see why it would be very hard to achieve in 3D rendering.

Best,
Jason.

[tom]

When I use coatings I can use a fine (high rez) bump map to create "roughness" because the texture of the BSDF is inherited by the coating... is this not good enough?

Sure, I'd suggest doing the same. It's just in risk of causing faceting when the frequency of noise is high.

However as I say it would take the naked eye to really see it -- sort of like the iridescence varnished wood grain sometimes has as you tilt it... nearly impossible to see with anything but the naked eye but a very real part of the charm of wood. It's a very "rich" look... but I can see why it would be very hard to achieve in 3D rendering.

I see. Please check these 2 examples:

http://resources.maxwellrender.com/sear ... v2=0&tipo=

http://resources.maxwellrender.com/sear ... v2=0&tipo=

People usually fall in a huge mistake in material creation. They add a specular layer and think it's a good idea breaking the mirror perfection simply by increasing its roughness. That's actually what makes 98 of 100 materials look synthetic and unreal. Therefore, mapping is quite essential. Because, the surfaces are closer to being irregular and specular than regular and rough.

[Tok_Tok]

People usually fall in a huge mistake in material creation. They add a specular layer and think it's a good idea breaking the mirror perfection simply by increasing its roughness. That's actually what makes 98 of 100 materials look synthetic and unreal. Therefore, mapping is quite essential. Because, the surfaces are closer to being irregular and specular than regular and rough.

I think this is a good example of creating rough materials without have to use the roughness setting, i did this material a while ago:

http://www.maxwellrender.com/forum/view ... 97&t=34190

The metal looks rough but that's only because of the many scratches, the roughness of the chrome is 3.0.

[Half Life]

Tom, thanks for the recommendations -- I'll download and play with them tomorrow.

Tok_Tok, I saw you making that chrome (thanks for sharing)... very cool final effect and definitely goes into my bag of tricks;)

I just spent a bit experimenting with thin sss (and regular sss) as a coating (to fill gaps made by neg. bump in the underlying BSDF) -- I couldn't get it to look right... too transparent, not enough color particles to get the effect I was thinking of.

Interesting effect though.

Best,
Jason.