Iray Depth Canvas not working?
SnowSultan
Posts: 3,773
in The Commons
I understand Iray canvases fairly well (I wrote this tutorial too: http://fav.me/d9cro54), but no matter what I try, I cannot get the Depth or Distance canvas types to render anything. Are these not implemented yet or is there something specific that needs to be done in order for them to work properly?
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There has been some discussion about this in another thread:
http://www.daz3d.com/forums/discussion/65444/has-anybody-else-submitted-this-depth-canvas-bug#latest
Whether or not you are having the same issue, Esemwy is definitely in the know when it comes to canvases.
Hope this helps!
- Greg
Hm, Esemwy was at least able to get a Depth render of some sort. I only get a fully transparent render when I try. Thanks for that link though, it seems that even when it works, it's not as useful for artistic use as people would like it to be.
Yeah I haven't really had much luck with any sort of environmental effects in Iray yet (godrays, fog, depth, etc). I've tried two free presets that used SSS to simulate godrays and fog, but they gave unusual and somewhat unpredictable results. Not that it's a huge problem anyway, doing them in Photoshop gives you complete control and saves render time.
I've been enjoying use of haze effects in Iray, but I'm somewhat uncertain whether it's worth the processing time vs. doing a depth 3dl and handling it in post.
I've not gotten all-transparent, but all-white or all-black on some of these canvases is predictable due to their 32-bit nature. You don't get this with the Beauty canvas, but you delifintely need to process the resulting EXR (not the image in the standard render window) in a program like Photoshop to adjust the HDR Toning. You can play with the Method setting (e.g. Equalize Histogram) to see what gives you the best results.
There's no node setting for Depth, or Alpha option, which could explain an all-transparent image, but something doesn't sound right here. FWIW, I tend to render these canvases more-or-less separately. I've seen some strange behavior when you pile on the different canvases for one render.
So to answer the question, I can get Depth to work, and it yields a grayscale depth map. It's just not very useful, IMO, for the kind of compositing work I do.
I also prefer to simply add these in Photoshop. Takes half a minute.
BUT... it's something of a challenge to get volumetric effects to work in Iray, which though supports volumes, does a really crappy job at it. If you haven't already, check out this thread:
http://www.daz3d.com/forums/discussion/62589/looking-for-iray-mdl-examples-for-vdf
One upshot with all the experimentation is that Iray can't accept a map (or map-like values such as from a procedural noise generator) to aid in constructing variable volume effects, such as the type you'd see in fog or a cloud.
The SSS settings are really just triggering the VDF functions in Iray, but the Uber shader can be very complex and hard to deconstruct. It turns out there are several VDF-based shaders in the NVIDIA examples folder. One is the red wax thingie, which does a pretty good job at making simple fog, God ray, and other effects. Since this shader is simpler, it tends to be a little faster.
I also discovered that while the absorption and scattering coefficient nodes can't accept a map, the Refraction Weight node can (in Iray Uber) can, and that one can produce some variability in the volume effect. For best results, the texture you apply here should be designed for the specific geometry. The texture is mostly white with slightly dark spots for where you want there to be a little more thickness. It's not perfect, and not as good as what 3DL can do, but it might work for certain effects.
As far as I can tell, depth canvases are only useful if you don't have any transparency in your scene. If that's the case, all you have to do is "Image->Adjustments->Tone Map..." the canvas in photoshop. "Equalize Histogram" seems to give the best results. If you're really desperate, you can render enough alpha layers to help reconstruct the depth map by painting it.
When all is said and done, as Will said, using the AoA depth camera in 3dl is probably your best bet.
One thing I've tried is using displacement maps on the fog object. It's... ok.
I've also had a lot of fun applying fog to liquid and other organic shapes (Soldiers of Serpio, for example). That helps provide some variation that 'feels' more appropriate.
As a point of interest, @jag11 reports in another thread that the new Iray version that comes with 4.9 supports better volumetric effects. Haven't tried it yet myself, but anything would be an improvement.
After using the method Esemwy described in http://www.daz3d.com/forums/discussion/65444/has-anybody-else-submitted-this-depth-canvas-bug#latest, I was finally able to get a depth image after the hdr toning in Photoshop. Looks like more is involved though, so will keep experimenting.