Everything related to http://resources.maxwellrender.com
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By eric nixon
#381778
Hi all, I watched this thea vid which explains well the concept of micro-roughness.

https://www.youtube.com/watch?v=Z01biJCEiKY

And I thought there is probaby a way to do that in maxwell. The only way I found which doesn't incur a speed penalty and appears to work, is blending multiple spec bsdf's with varying roughness and R2 angles, In my test I used 4 bsdf's.

Anyway here is a quick test, 10mins sl18, rendering much faster than the thea approach (although I expect their more correct method may yield subtle benefits)

Image
By numerobis
#381779
interesting! I saw this Thea video too and thought about the same - to create this effect with multiple BSDFs - but i didn't try it yet.
By bograt
#381791
I use this technique in Maxwell too... Vray, corona etc support falloff in the roughness slot which is nice, it would be great to see this in Maxwell one day
User avatar
By eric nixon
#381797
Please, can you tell us more about your approach / results / issues, and show a picture maybe. I'm a bit busy to test this right now, but it is promising.
By hatts
#381820
That blue wall looks outstanding. Actually I can't remember the last time I saw a surface with multiple offset reflections like that, captured decently in rendering.
By photomg1
#381842
Awesome

Once again, you leave me head scratching, how have you achieved that eric. I can do it in modo using a custom gradient with an input parameter based on incidence angle to control roughness . But I'm clueless as to how you have achieved that in maxwell even though you have mentioned R2 .Its the fall off in the roughness I don't get which is affected by viewing angle, I know R2 is for a custom control how ref 0 and ref 90 are blended. How have you managed to get that to drive roughness or in this case I presume visibility of a layer is what's got me. Props to you sir !

As been as this has been posted in resources is there any chance you could post the mxm ?

best

Matt
By numerobis
#381847
bograt wrote:Vray, corona etc support falloff in the roughness slot which is nice, it would be great to see this in Maxwell one day
+1 and a curve instead of these R2 values...
User avatar
By ababak
#381849
Matt, I think that effect can be achieved if you set Ref 0 to black and Ref 90 to white. R2 will control the falloff. You can make several BSDFs with roughness of 25, 50, 75 and R2 will control at which angle they should start to reflect the light. I don't have time to create the scene for testing right now though.
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By Mihai
#381853
This is a great example. Just want to add that you have further control using the nD to get the "natural" fresnel based falloff, in addition to the r2 parameter. Just make sure not to use Force fresnel if you want to also use the r2 parameter.
User avatar
By eric nixon
#381858
Bruno, thanks for the compliment... it is just the emitters lighting the wall... one request; can you edit your post, because those renders block up this thread (which you say is useful) and the renders are not actually informative.

Anyway I had a chance to tweak the material, It wasn't possible to tweak using numbers/logic so I saved a preview mxs to tweak interactively, by eye.

New setup is 5 bsdf's (render speed unchanged), 3 for grazing angles and 2 for frontal angles, you cant make a midway bsdf, (one where the brightest spec was around 45 degrees with darker front and grazing... it cant be done).

There is also a very gentle normal map to make the wall 'un-flat', which causes that anisotropic effect. (was present in the first setup too)

Image

http://www.mediafire.com/download/ea434 ... ess_5x.mxm

(this material makes no claims to physical accuracy :!: )

Simball sl15 5mins;
Image


I think a function in maxwell to do fresnel-roughness in a correct way would be nice, but if the fake way renders faster.... I would stick with that. The spec can be adjusted easily in terms of smoothness, and the intensity controlled via layer weighting.

Thanks all for kind words. Its great to see so much interest in this subject, shame Bograt went quiet?
By photomg1
#381864
Thanks for sharing Eric !!!

edit:

here was my version settings : ) a bit simpler but hey it worked :D


Image Image
Image


best

Matt
User avatar
By zparrish
#382311
Hey Eric,
First off, great post man! While looking for a totally unrelated subject in the forums, I found this post and it actually addresses the core issue of a feature request I posted for Layer Blending by Viewing Angle:

http://www.maxwellrender.com/forum/view ... =2&t=42667

The MXM file you provided is much more successful than any of the attempts I tried previously. It also partially handles something that I didn't think of at all; the double reflection as mentioned in the Thea Render video. The plastic surface I'm trying to replicate is rough enough and it's "micro roughness" doesn't appear to create a double reflection. I'm only looking at a 6" sample of it, and it's only about 1-3/4" wide, so perhaps it would happen on a larger version of the material.

Now I just have to apply this same thought process to a version of my gasket. The most intriguing part of your MXM values that I find are the weight values you selected for your specular contributions. Was that done purely by eye or is there a method to the madness? You specifically state that there is no claim of physical accuracy with your MXM file. I'm assuming that's mostly in reference to the additive layer blending adding up to more than 100, opening up the possibility of reflecting more light than is received by the surface. However, the stack of specular BSDF's will proportionally even themselves out within that layer, if I understand the Maxwell docs correctly. Also, there are some rather wild Nd, and K values in your BSDF's :D

Thanks again Eric for sharing this!
User avatar
By eric nixon
#382332
Ok so, the material is a hack to achieve a certain visual effect, some of the values will have little to no influence on the material, and the values may need to be at their extremes (or the values may be having no effect at all, in which case I just left them at some random value). Notice all the spec uses R2. R2 is hack territory, normal rules no longer apply, R2 bsdf's are darker and no longer add up to 100%.

The material is built with a certain logic but the weight levels are adjusted interactively by eye via fire in mxed.

Thanks for the compliments.
Texture/finish lost in render.

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