Peach Skin and such view dependant effects

[ray]

Would anyone have found a technique to achieve lighter silhouette of objects that would depend on the angle between view and object normals. This is something I like to do for many effects I won't mention here because we are still in a "physically correct" territory, so let's just pretend I only want to make a peach skin
I think what I want could be imagined as using the fresnel effect for diffuse reflection instead of glossy. but there might be ways already available to do this?

[heretic]

Hi ray,

as promised my suggestion. We talked about velvet, but the effect is similar for peach.

Remarks upfront:

• some areas look greasy, am sure this can be changed too - but imho this is part of that "velvet effect" and is exactly what makes this sort of material so special.
• its not perfect but the way I understood you, this is the effect you are lookign for (esspecially as seen on the upper right corner).
• it was more difficult in luxRender than I thought - granted

Hope this helps and is what you are looking for.

heretic


My scene view in clay render with some remarks (basically its a cloth-sim to ensure we have loads of different view angles on the fabric):

clay + remark

render 1 - directly from LuxGUI after tonemapping:

render 1 - LuxGUI

render 1 - tonemapped externally:

render 1 - external tonemapping

render 2 - flipped materials - directly from LuxGUI:

render 2 - flipped materials - tonemapped externally:

How it was done:

• a matte material
• a glossy material
• both materials put together in a mix material with a "pattern map"
• mix material bumped with the pattern map as the bump map
• sizes were calculated as app: dots on pattern map = 0.25mm, bump = 4 * dot size (so bump height was app. 1mm)

Remark:
- basically these are cylinder primitives perpendicular to the surface normal
- this is actually almost like velvet is made in real (cut loops in the fabric of either cotton or silk)

The mix material:

The "pattern" to mix and bump:

[heretic]

ack had noise reduction on (even though we wanted/needed the noise) - rerendering with slightly different settings.

[heretic]

transcript <snipped> from irc on this topic:

[14:14] <LordCrc> _heretic: tbh i didnt understand what exactly the suggestion was heh
[14:15] <_heretic> the bump/pattern beign the same
[14:15] <_heretic> bumping one mix material up
[14:15] <LordCrc> ah
[14:15] <_heretic> basically I made cylinder primitives
[14:15] <_heretic> upper part material 1
[14:15] <_heretic> lower part material 2
[14:16] <_heretic> lower part = ground
[14:16] <LordCrc> ah right
[14:16] <_heretic> call the idea: "ray catching"
[14:16] <_heretic>
[14:16] <_heretic> ray catchign at specific anggles
[14:17] <_heretic> -g
[14:18] <_heretic> LordCrc: you can tell if you look at it a different way am all in for blunt critique
[14:19] <LordCrc> heh
[14:19] <LordCrc> well i think we should have a velvet material in any case
[14:19] <LordCrc> ive been trying to find one
[14:20] <LordCrc> doesnt seem to be a lot out there

<snip>

[14:21] <jensverwiebe> _heretic: ever tried a velvet with hair ( extreme short indeed )
[14:21] <jensverwiebe> ?
[14:21] <_heretic> jensverwiebe: yes, that works much better, but too much primitves needed
[14:21] <_heretic> kills any computing time
[14:22] <jensverwiebe> brb
[14:23] <_heretic> jensverwiebe: in that case it imho makes sense to have a matte transmitter and either glossy or mattetransl hair
[14:23] <_heretic> errr matte emitter

[ray]

Thanks heretic. This looks nice, I tried hard to customize it, but other than copying it, I failed to control it and get the real contrasty falloff I would have wanted.

[heretic]

Thanks heretic. This looks nice, I tried hard to customize it, but other than copying it, I failed to control it and get the real contrasty falloff I would have wanted.

For real contrasty Id try it slightly different:

- create a second "pattern" texture: white ground, a black circle 1-2 px width around each circle of the current pattern (ideally 1px of the current outside, one pixel of the current inside). In PS I would do that, by applying a 1-2 px blur (to have each black circle of the current black dots with a grey line) and then select all true black and make it white Afterwards just make all grey black and you are done.
- mix the current mix-material with another glossy (or matte woulda have to try) and use the new 2nd pattern texture as mix texture (the old pattern texture is kept on the first mix material), whereas the old pattern is the bump texture (all the same for all materials)
- the new additional material controls the shiny 2nd color (our third material we added), height of the bumps controls the amount

Voila

What would that do?
- with the current bump we make little cylinders on the surface, but we didnt control the color of those cylinder primitive faces opposed to surface normals
- the new 2nd pattern texture would control the cylinder face material, which would be perpendicular to the surface normal

Result:
- looking upside down you only see the materials of the first mix material (and some color bleed)
- at different angles the 3rd material would be seen in addition

[heretic]

PS: to add some "beauty" Id propably make the dots random on the base pattern with same density (eg. modified mosaique pattern in PS with bright lines between each)

PPS: am just rendering my own stuff hence am quite reluctant to render different things - nonetheless I created the 2nd pattern texture for you - imho it should fit - see attachment (it is made to fit with the first pattern texture - please verify)

[ray]

I'm trying with second mix. Do I have to copy each option of the first material or is there a dropdown that I missed where we can simply pick two existing materials to mix like we can do in Yafaray? (the two texture files do match)

[heretic]

I'm trying with second mix. Do I have to copy each option of the first material or is there a dropdown that I missed where we can simply pick two existing materials to mix like we can do in Yafaray? (the two texture files do match)

just click copy on the approbriate slot (blender exporter)

[ray]

just click copy on the approbriate slot (blender exporter)

You mean the rollout from where to chose glossy, matte, etc...? Existing materials don't appear there. No big deal for now though, I rebuilt the materials to mix.


Now that I put it in place, I think I understand your technique.
If i do, it's pushing bump mapping to its limit towards infinitely small scales, just like a few years ago, when blurry reflections where not available in every renderer, we sometimes used tiny noise bump maps to get them. Only Here, to my humble noob's eyes, things look the other way around:
normal dependant gradients and slope patterns have been available in pretty much every other renderer for quite a while, maybe they are not physically correct?

However all this is pretty interesting and another step in the right direction but it might still be a dead end.

If I want the fibers to be so small as to be individually invisible and to appear just one continuous gradient, is it possible with your technique? (I am waiting for this to "converge" on my slow machine and with my little knowledge of Lux optimization so I might never get something good enough to post but I'll try to let you know)