Hi,

"Ambient Occlusion", as its name implies, is a technique invented to gather the occlusion of ambient lighting (and nothing else).

An ambient occlusion map should then only affect ambient lighting, like 'Ambient' and 'IBL', but certainly not the diffuse lighting produced by Lights.

Here is an illustration, a character with Skin_Head channel without AO (well with the map but with strength at 0):
 

And now with the Ambient Occlusion map and strength 100, again on the Skin_Head channel:


The result is completely black !?

This should not be, only the Ambient and IBL lighting should be affected by the black AO map, we should still see the Key and Rim lights diffuse lighting on the head.

--
guy rabiller | GOETZIWOOD STUDIOS
"N.O.E." (Nations Of Earth) Sci-Fi TV Show, Showrunner.

This strikes me as similar to using the reflection channel. It's not really reflection at all, but a mapped-on image. It is a "baked" AO. For real-time AO, you would use the AO in the visual section. So, it is basically an overlay channel.

It is a question of how the data is used rather of where the data comes from.

A Reflection channel is meant to be a "Reflection Mapping" channel, as in the old day when raytraced reflection was too expensive to perform. Instead of tracing a ray in the scene from the reflection point and direction, a simple lookup is performed in the reflection map (as for ambient in an environment map, but done in the normal direction instead of the reflection direction).
But both, reflection mapping data and raytraced data are used the same way.

Same for AO, whether you use a "baked" Ambient Occlusion map or a "realtime" Ambient Occlusion like SSAO, the resulting data should be used the same way: multiplied by the ambient lighting, and ambient lighting only.

In short, "Ambient Occlusion" should deal with "Ambient" only.

--
guy rabiller | GOETZIWOOD STUDIOS
"N.O.E." (Nations Of Earth) Sci-Fi TV Show, Showrunner.

It is pretty much like the Blend channel, actually. It is additional an texture channel that contributes its brightness values (it strips out color). If you load an actual AO map instead of solid black, you will then have your baked AO as part of your texture.

If you set the diffuse to black, you also end up with a texture that shows no lighting.

Think of it as a Photoshop layer, I guess.

I don't know how other applications do it, but I like the logic in Grabiller's post.

The question seems to be:  "Where in the sequence of operations do you multiply the lighting by the ambient occlusion?"
Option 1 - Add all lighting together first, then multiply by ambient occlusion map.... (a+b+c+d) x  AO
Option 2 - Multiply ambient light by ambient occlusion map first, then add other light sources to that result....  (a x AO) + b + c + d

It appears iClone uses Option 1, but Option 2 sounds reasonable, and is what I think Grabiller is suggesting it ought to be.

---

iClone 7... Character Creator... Substance Designer/Painter... Blender... Audacity...
Desktop (homebuilt) - Windows 10, Ryzen 9 3900x CPU, GTX 1080 GPU (8GB), 32GB RAM, Asus X570 Pro motherboard, 2TB SSD, terabytes of disk space, dual  monitors.
Laptop - Windows 10, MSI GS63VR STEALTH-252, 16GB RAM, GTX 1060 (6GB), 256GB SSD and 1TB HDD

@justaviking
Exactly! ^^

--
guy rabiller | GOETZIWOOD STUDIOS
"N.O.E." (Nations Of Earth) Sci-Fi TV Show, Showrunner.

Sounds like a good issue for FeedBack Tracker.

If you know what is "industry standard" (and iClone doesn't follow it), it might be legitimately called a bug.

(Feel free to use any of my post verbatim, or as inspiration, if you think it'll help.)

---

iClone 7... Character Creator... Substance Designer/Painter... Blender... Audacity...
Desktop (homebuilt) - Windows 10, Ryzen 9 3900x CPU, GTX 1080 GPU (8GB), 32GB RAM, Asus X570 Pro motherboard, 2TB SSD, terabytes of disk space, dual  monitors.
Laptop - Windows 10, MSI GS63VR STEALTH-252, 16GB RAM, GTX 1060 (6GB), 256GB SSD and 1TB HDD

I think this requires some thought, because I never use IC6 style ambient lighting, which to me make things look flat. I do like the AO settings in the Visual tab, which are sort of a poor man's AO.

With GI announced for IC7, there is ambient lighting from whatever emitting sources there are, resulting, in a much improved look. 

I think we run in a snag here, because we cannot refer to IC7 at this point. But I would suggest waiting to call this a bug or not until the new illumination system can be reviewed officially and in its entirety.

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@animagic
You are right we cannot refer to IC7 at this point, but nonetheless CC2 is meant to design characters and their looks.

This implies the use of materials and texture channels. Each texture channel should then behave correctly, which is apparently the case for the new PBR channels (Base Color or Albedo, Metallic and Roughness).

This should also be the case for AO but unfortunately this is not the case. In CC2, there is clearly a misuse of the ambient occlusion texture channel which should only affect ambient lighting (Ambient, IBL, GI, ..) but certainly not Diffuse (direct) lighting. This is not "guess work" I'm talking about, this is the rule: AO is for Ambient Lighting. (there are exceptional uses of AO with Diffuse but we enter another domain, where peoples know what they are doing). AO has been developed by ILM to create realistic ambient lighting. A Diffuse lighting impacted by AO is ruined, period. And CC2 is not the only one making that mistake, especially some other realtime engines with SSAO do the same mistake (and iClone does the same mistake with its own SSAO).

So we may not call it a bug per say, because the current AO behavior in CC2 may be intentional. But if then, then this is a clear misuse of AO, an absolute error in 3d lighting technology.

If this stays that way, especially in iClone7, then the PBR and GI features themselves will be ruined by the lack of proper use of AO. (the other point which will ruin the PBR and GI features are the shadowing and diffuse issues on transparent surfaces if not fixed as well, but that's another thread).

--
guy rabiller | GOETZIWOOD STUDIOS
"N.O.E." (Nations Of Earth) Sci-Fi TV Show, Showrunner.

the actual iclone piece has always had an extra AO feature in the panel with the shadows etc etc so I am assuming their AO is as mentioned above like the blend channel so you add that and turn up the internal AO on that features panel which I forget the name of. ... sorry to ramble I have never been a technical person as far is making sure all the terminology is right I tend to explain stuff to myself so they stick and that is the terminology I remember.   I have a lot of "thingies" in my terminology LOL.  

I am pretty sure in watching those new videos i saw the same AO feature in the panel with the shadows etc fly by..  




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