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Revanto
08-08-2018, 08:04 PM
I have been trying to put together e little guide for myself on how to fake certain passes using a raytrace renderer (sepecifically in terms of older 3d programs) so they could be composited later and achieve modern PBR rendered results.

Anyway, I came across this page https://colinbarrebrisebois.com/2011/04/04/approximating-translucency-part-ii-addendum-to-gdc-2011-talk-gpu-pro-2-article/

I tried to render out an AO pass using a model with flipped normals but, unfortunately, all I got was a black render of where the object should be. No matter what settings I fiddled with, I got the same result.

It's an easy thing to replicate if you want to try it yourself. Just flip the normals of any model then try to render out an AO pass.

So, does anyone know how I can get it to render like it outlines in the paper from the link?

Maybe there is something obvious or stupid I am missing or there is another way of achieving this. Just to let you know, though, that just inverting the AO pass on the same model with the normals facing outwards normally won't do the trick because, apparently, the result is not actually the same.

Appreciate any input.

Cheers,
Revanto :p

PS: I finally watched Infinity War last night and it was great. It's amazing how well the visual effects came out when all they used were Poser and Gimp ;D

Tobian
08-09-2018, 06:53 AM
Hmm, we'd have to ask for it, it's not currently a feature of the native occlusion node, and i wanted it for other reasons also.

Revanto
08-09-2018, 07:46 PM
I'm not using a node. This is just a basic AO pass. I'm just wondering WHY it is not working because only thing the normals are flipped. If light can penetrate normally from the backface of polygons then why shouldn't we get a result with flipped normals?

Surely there should be some way of dealing with this?

Revanto

Sensei
08-10-2018, 01:10 AM
I would try this:
- no flipping of polygons
- in LW 2015.3 use my node, from TrueArt's Node Library (http://nodelibrary.trueart.eu), or Denis node to override normal vector
- have nodal network like: AO -> Normal Overrider -> Diffuse Shading
(basically only AO node must know about normal overriding, and nothing else)

Tobian
08-10-2018, 02:33 AM
Right, there's several tricks you can do in the old node editor, but in 2018 there's no method I am aware of.

Sensei
08-10-2018, 04:30 AM
Right, there's several tricks you can do in the old node editor, but in 2018 there's no method I am aware of.

Try:
Occlusion node to Standard material, set Luminosity 100%, the all other 0%.
Take Perturbed Normal, to Math > Vector > Scale -100%, then to Normal input.

Tobian
08-10-2018, 05:11 AM
Sure you can do that, but you can't do anything but bake that, as you can't flatten the outputs of the integrators for use as shader inputs. Natively. But that is one way to do it, i will have a play.

Revanto
08-10-2018, 08:00 PM
It might seem selfish to say this but I am trying to set this up so that it works on older versions of 3d programs. My original intention for this was to try to make all the necessary passes in old programs (that still have some of the basic functions like AO, fresnel, etc...) and not have to rely on commercial plugins, additional nodes, etc... It's a matter of using old school methods to obtain the passes necessary to get a more realistic PBR result. This would include basic Photoshop tricks as well. While it is for Lightwave for my sake, it is something I would like to try have apply to other old 3d programs.

The reasoning behind this is that I want a layman's approach to texturing and lighting via compositing. I've always sucked at both but since the introduction of PBR, I've slowly gotten a better understanding of how lighting works in the real world. If I can put together some sort of guide for other people like me who respond better to a more layman's way of thinking then maybe I can untangle the knot they may have by being confused with all the info and terminology on the subject of PBR and real world lighting. I think that the easier you explain something to someone then that info gets absorbed into their heads more easily and this can help in learning other things that are relative more easily, too.

I still have a ton of learning about the subject but it is something I honestly want to translate into layman's terms through the medium of compositing.

I appreciate the input provided so far to a degree but I don't think the discussion is going as I was expecting it to.

Sorry about the misunderstanding.

Revanto

Tobian
08-11-2018, 05:56 AM
Btw, sensei, I tried that last night, and it doesn't work in 2018, using the native occlusion, it just outputs black.

And there's nothing wrong with 'hacks', they can often produce useful textures that you can use for all sorts of things. 'Occlusion' is a bit of a hack, just incredibly useful!

Sensei
08-11-2018, 07:41 AM
Btw, sensei, I tried that last night, and it doesn't work in 2018, using the native occlusion, it just outputs black.

Try double clicking Occlusion node, and change Mode from Infinite, to Ranged, and adjust Max range..

Max Range Infinite must result in black output, as ray always has to hit surface when it's fired from inside of object.
Check also Double Sided option.

Tobian
08-11-2018, 10:41 AM
Tried it all. You show me, I tried everything.

Sensei
08-11-2018, 11:23 PM
When I was testing it, I made Torus using Modeler tools in Layout, and set up like I described, even with default 1m Range, it's not black:

142485

Tobian
08-12-2018, 01:39 AM
Hmm, it still has issues. I'll try again, I couldn't get anything but black, May be the object scale was an issue.

jwiede
08-12-2018, 08:29 PM
Hmm, it still has issues. I'll try again, I couldn't get anything but black, May be the object scale was an issue.

Sensei's using 2018.0.4 judging by his screen capture, if you're using a later revision (.0.5 or .0.6) it's also possible there's been a regression since .0.4.