PDA

View Full Version : ZBrush4 -> LW: Ambient Occlusion Node Setup



BlueApple
12-12-2010, 10:47 AM
I've been working in ZB4 and exporting meshes and maps to LW. How do you all use the Ambient Occlusion pass in your node setup? I've been plugging it into different spots and not seen any real useful results. What is a common method of using the AO pass?

probiner
12-12-2010, 10:55 AM
It's normally plugged into Diffusion, i think.

From what i see in the image, the AmbOcc map you have there has very mild values. I can't spot the mouth, for example, in there.

Cheers

gordonrobb
12-12-2010, 03:44 PM
I would say the diffuse.

BlueApple
12-12-2010, 03:49 PM
Thanks for the replies. I rendered some tests out running it into diffuse (see below). Also, I used a math node to increase the effect, but I'll take a look at ZBrush and see if I can't generate a higher contrast map from the start. Thanks for the help.

probiner
12-12-2010, 04:19 PM
I would say the diffuse. yes that =P

Why is it so dark with default image BlueApple? Colors are actually dark or the lightning is strange?
Well either way the last one looks a bit nuked.

I'm not saying it needs more contrast, i was just refering that i couldn't spot the mouth in that little picture, so maybe something is wrong with the AmbOcc calculation. But hard to say with such small picture.

Cheers

jasonwestmas
12-12-2010, 05:05 PM
The physically accurate way is to have the AO map effect the ambient shading in the lighting effect. It's supposed to simulate the detailed shadowing you get from global illumination. LW has no way of doing this without GI so I tend to use the AO map as a color base and/or diffuse map in a balanced/ stylized kind of way. I don't go to LW for physically accurate rendering anyway.

BlueApple
12-13-2010, 05:54 AM
probiner: it's pretty dark in the default scene because I hadn't bothered to properly light it yet :). I just wanted to do a test to see what the AO pass plugged into the diffuse would deliver. I agree the last one looks pretty nuked; I would dial it back to around 1.2 times intensity rather than 4. The map is attached if you want to check it out.

jasonwestmas: thanks for your comment. I may end up blending the AO pass in Photoshop with the color texture to adjust the image prior to rendering.

gordonrobb
12-13-2010, 06:04 AM
Have you tried just sticking a normal Occlusion node onto the diffuse channel rather than using ZBrush output?

MUCUS
12-13-2010, 07:53 AM
Yes Zbrush Aoc map may be here to allow you not to use an Ambient occlusion shader. So linked it to the diffuse channel is a bit like doing 2 times the same thing, isn't it?

You could compose it in Photoshop with your color map or play a bit with LW incrustation method...or as Gordon says, just use LW ambient occlusion and give up your map.:)

Sensei
12-13-2010, 11:36 AM
probiner: it's pretty dark in the default scene because I hadn't bothered to properly light it yet :).

I don't think so it's lighting problem, because eyes are showed correctly yellow. With wrong lighting, they would be affected too as the rest of character. Original body texture is definitely too dark.

Ambient Occlusion texture should be plugged to Gradient node, and output from it to Diffuse. This way you will be able to set lowest, middle and highest values. And have non-linear interpretation of AmbOcc.

BlueApple
12-14-2010, 06:17 AM
I'll try running the AO texture through a gradient node and see what I get. BTW, the eyes are semi-luminous so that is why they are coming out far brighter than everything else. That said, the texture is a bit dark in the blue regions (face, belly, etc.) and I will be applying some specular highlights to define the shapes, lightening up the map and probably doing some cleanup in Photoshop.

Thanks again for all of the replies.

jasonwestmas
12-14-2010, 07:41 AM
You could try using the Lightwave Ambient Occlusion Node to surface bake an AO map. Personally, I find the Zbrush AO mask insufficient and lacking value.

gerardstrada
12-14-2010, 05:25 PM
What you have there is an Occ map, an AO map would include the ambient an the occlusion component in a single map. As Jasonwestmas says, correct way is to affect the ambient component. Idea is to multiply the AO component with the ambient component (a Scalar node - vector type - may work faster) and then add/screen this output to the direct lighting component. However there's at least a couple of ways to do this in LW without GI. One is with DP ColorBleed node, set Occ to 0% and Backdrop to 100% to get the ambient component only - the Bleed Amount controls the local bounces by separate - you can set up this locally in Surface Node Editor, or globally in DP_Filter Node Editors and bake it in a map with SB camera. Other way to get only the ambient component is through a lights rig (IBL) with shadows disabled. I remember a couple of shaders that faked this, too. With GI, the proper way is by multiplying a RO pass/map with an ambient pass/map + irradiance pass/map, we can get these passes/maps through DP_Filter Node Editors. You may check also the Issue #30 of HDRI3D magazine (http://www.hdri3d.com/index.php?option=com_content&view=category&layout=blog&id=163&Itemid=100) to learn how to export these passes/maps in a single render with DP_FNEs). There are ways also to get the whole indirect lighting pass from GI (ambience+irradiance components) in a single pass/map to be mixed with a Occ map/pass. In that case, this thread (http://www.spinquad.com/forums/showthread.php?19309-New-options-for-Render-Management&p=212442&viewfull=1#post212442) could give you more ideas.



Gerardo

jasonwestmas
12-14-2010, 05:49 PM
Yeah I keep forgetting about those Dpont nodes. Thanks for filling in the details Gerardo and thanks a bunch for the HDRI articles!

caesar
12-14-2010, 06:09 PM
What you have there is an Occ map, an AO map would include the ambient an the occlusion component in a single map. As Jasonwestmas says, correct way is to affect the ambient component. Idea is to multiply the AO component with the ambient component (a Scalar node - vector type - may work faster) and then add/screen this output to the direct lighting component. However there's at least a couple of ways to do this in LW without GI. One is with DP ColorBleed node, set Occ to 0% and Backdrop to 100% to get the ambient component only - the Bleed Amount controls the local bounces by separate - you can set up this locally in Surface Node Editor, or globally in DP_Filter Node Editors and bake it in a map with SB camera. Other way to get only the ambient component is through a lights rig (IBL) with shadows disabled. I remember a couple of shaders that faked this, too. With GI, the proper way is by multiplying a RO pass/map with an ambient pass/map + irradiance pass/map, we can get these passes/maps through DP_Filter Node Editors. You may check also the Issue #30 of HDRI3D magazine (http://www.hdri3d.com/index.php?option=com_content&view=category&layout=blog&id=163&Itemid=100) to learn how to export these passes/maps in a single render with DP_FNEs). There are ways also to get the whole indirect lighting pass from GI (ambience+irradiance components) in a single pass/map to be mixed with a Occ map/pass. In that case, this thread (http://www.spinquad.com/forums/showthread.php?19309-New-options-for-Render-Management&p=212442&viewfull=1#post212442) could give you more ideas.



Gerardo

I think Gerardo should be part of the Core team, hes just a LW/CG genius!

probiner
12-14-2010, 06:25 PM
Gerardo the Occ map, without the ambient component is the called Cavity map?

Thanks

gerardstrada
12-14-2010, 10:28 PM
Jasonwestmas, thanks to Denis Pontonnier for these great tools!

Caesar, thanks! but I think Denis is who indeed deserves those comments :beerchug: (...and be in the Core developer team)

Probiner, I know the the Occ map without the ambient component as just an Occlusion map. I think the Cavity shader in ZBrush is a sort of a surface differentials shader, something that we could get with DP Curvatures driven by a Gradient.



Gerardo

probiner
12-14-2010, 10:45 PM
Jasonwestmas, thanks to Denis Pontonnier for these great tools!

Caesar, thanks! but I think Denis is who indeed deserves those comments :beerchug: (...and be in the Core developer team)

Probiner, I know the the Occ map without the ambient component as just an Occlusion map. I think the Cavity shader in ZBrush is a sort of a surface differentials shader, something that we could get with DP Curvatures driven by a Gradient.

Gerardo

I see, thats what i thought also about DP-Curvatures.

But i'm relly not getting the difference between an AmbOcc map and a just Occ map. Googled and always shown up AmbOcc. Can you share examples?

Thanks again.

BlueApple
12-15-2010, 08:29 AM
@gerardstrada: Thanks for the response. I will get to reading those links tonight.

jasonwestmas
12-15-2010, 08:31 AM
Jasonwestmas, thanks to Denis Pontonnier for these great tools!
Gerardo

Oh yeah, I definitely have thanked him in the past, maybe a nice letter would work better than on these forums though. :)

gerardstrada
12-15-2010, 02:12 PM
Ok. This would be an Occlusion pass:
http://imagic.ddgenvivo.tv/forums/FNE/article/Op.jpg

This would be an Ambient pass:
http://imagic.ddgenvivo.tv/forums/FNE/article/AMBp.jpg

And this would be an Ambient Occlusion (AO) pass:
http://imagic.ddgenvivo.tv/forums/FNE/article/AOp.jpg

This would be a light warping pass (from DP Curvatures shader):
http://imagic.ddgenvivo.tv/forums/FNE/article/LWp.jpg
which driven with a gradient can be used as a cavity pass.



Gerardo

P.D. Btw, the ambience pass without the diffuse component would be something like this:
http://imagic.ddgenvivo.tv/forums/FNE/article/AMBpNDC.jpg

probiner
12-15-2010, 04:39 PM
Thanks Gerardo.
That Post Edit made it made even much more sense. Ty for the time to explain it.

Cheers