Glossy Roughness and The Human Figure
Patroklos
Posts: 533
The documentation Centre says;-
Glossy Roughness - The property controls the roughness of the surface. The higher the value, the less shine the surface will have. It can also be mapped with an image map to drive its strength.
It seems to me that the above is not an adequete explanation, and does not mention the most important thing that this setting does according to my observations.
I believe that this setting, above all else, governs the area that the glossiness covers. The higher the setting the greater the percentage area covered. This may be seen quite clearly by (temporarilly) setting Top Coat Weight to zero, setting Glossy Layered Weight to (say) 1.0, and with the Main Viewport set to Iray and the preview light on, changing the Glossy Roughness settings up and down. As you turn the setting up you will note, whilst Iray is initialising, it can be seen that a larger area becomes affected by glossyness untill at 1.0 the whole figure is glossy. Once Iray has initialised, you will note that as the picture develops, and assumimg that you have Glossy Layered Weight and Glossy Reflectivity set apropriatey high, that the glossy areas on the skin correspond to the glossy areas observed earlier.
It is not possible to do this directly using Top Coat, as the glossyness associated with Top Coat do not show up during the pre initialisation of Iray, however it should be possible to judge the areas to be affected by the Top Coat glossyness by experimenting with Glossy Layrered Weight as described above and transferring the settings across.
In this way it should be possible to make some judgements at an early stage regarding the areas of skin to be affected bythe two layers of glossyness.
Is the above correct, or am I misinterpreting what I am seeing?
Thanks
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Comments
I don't think the area percentage varies with glossy roughness, it always covers the whole texture if glossy weight is not mapped. It is just that a lower roughness will produce sharper shine, more concentrated; while higher roughness will spread the shine more.
In fact, if you reduce the glossy roughness to zero while not mapping the weight the whole figure will be bathed in shine; like water. The viewport preview can be deceiving in this.
What's an eye-opening experience is to set roughness to 0 and then use a noise map in bump, and tile it a lot. And hey, look, roughness.
I think that we are saying the same thing in a different way. I haven't tried the zero bit.
And I think that you two guys are making much the same point as each other. I will look at the effect of setting it to zero.
It's pretty funny, actually. You can do something similar in 3DL with reflection maps and bump (although tiling is trickier).
And you look at it and go oooooh. Roughness. Right. ;)
Now, mind you, roughness is more convenient, because with a different bump map, you essentially are creating two scales of bump -- microscale (roughness), macroscale (bump). And then anisotropy helps 'fake' a pattern of microscale bumps.
I have to tell you that you are going way above my head here!
Ok, here we go...
The first ball is perfectly glossy and reflective.
The second ball has a bump map (static) applied to it, which breaks up the reflection.
The third and fourth ball, one has Roughness set to .1, the other has the bump map tiled 128x128 and a bump level of .03. I honestly forget which is which, and that's the point -- the effect of Roughness is identical to the effect of many very very very tiny bumps, like most rough surfaces.
The last ball has Roughness of .1 and then a big hexagonal bump map applied. The Roughness setting simulates lots of tiny little bumps. The regular bump map, now, is reflecting a distortion of the surface in a large, obvious way.
SOOOO... Roughness is a convenient cheat to render more simply, to handwave something about the surface of an item.
Thank you!
I wouldn't exactly call it a 'cheat'...it is a real surface property, just not at the scale we are used to thinking of.
For skin...think of it being at the cellular level...how even/flat the cell layer at the surface is.
My question is can we use this application of adding a noise map to say...give more depth and detail to skins that are lacking in that department?
Daniel
I think in the Iray skin big thread it's been suggested a few times that you can add bump maps like that to add more depth. I've had good luck with that and my WTP Bump shader and the like, but I think what you really want is to get a bump map and make sure to get a corresponding normal map, tile them a huge amount, and you'll have some sense of 'pores' and whatnot.
Thanks Will i will play with it.
Daniel