Hair issue
DarwinsMishap
Posts: 4,087
I was wondering- has anyone else had this issue with backlighting and transmapped hair? I have tried using the Iray shader base with some settings I've found in the forum as well as the Slosh UHT hair shaders for Iray and the strands are still showing the polys with the backlight.
hair issue.jpg
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I've just run into that issue with hair from another vendor. I have no idea what's going on or how to fix it. It only happens when the hair is backlit; environmental lighting, lighting from front or sides, that's all fine. Backlit, you get that hard edge from ... something.
Check the cutout opacity map...it needs to be uncompressed and have a gamma of 1.0. You check by clicking on the image in the surface and bringing up the selection dialogue box, then hit Image Editor.
That will tell Studio to use it as a black and white/greyscale control map and ignore whatever the 'type' setting is in the header info within the image file itself.
Unfortunately, that doesn't seem to have helped. (Also, where in Image Editor would you uncompress an image?) I set it to have a gamma of 1.0, hit accept because I have no idea what anything else in that window does, and I still have a hard halo on the top half of her hair. And only the top half, which is weird, because every single zone uses the same transmap.
The transmap was, it turned out, full color (16.7 million of 'em) so I converted it to grayscale TIF and tried again. Still had the hard halo. I'm not sure how much good converting it to TIF would do, since it started as a JPG and was already compressed, but it was the only other thing I could think of to try.
The image compression setting that needs to be adjusted is part of the Iray settings...I can't check right now, because the machine capable of running Iray is in use.
So I changed the light rig- made the back light off to the side instead, added an emitter and got rid of the issue at least.
Whatever this issue is, it's caused specifically by strong backlighting in Iray. Any other type of light doesn't seem to activate the issue. I can generally avoid backlighting specific hairs if needed, but I'd rather know how to fix the issue, if possible. Especially since, with older hairs, it's likely to come up with some frequency. There are things that 3Delight seems to tolerate well -- such as full color maps pretending to be grayscale -- that Iray can't tolerate at all.
The image where I outlined the issue I found: http://vwrangler.deviantart.com/art/Wild-Waves-and-Zahara-vs-Backlight-revised-558891862 (entirely worksafe, for a wonder)
The first two images are fine -- that first one looks really good, if I do say so myself -- but that third one ...
I found the texture compression setting, I think. It's under Advanced settings on the Render tab. I'm not sure how you could possibly turn it all the way off, or if you would want to, since it works on every texture in the scene and not just that specific one. I did shift it from min 512/max 1024 to min 1024/max 4096. Didn't help, unfortunately; didn't make any visible difference I could see. I still have the hard halo. I guess there are just some transmapped hairs that are going to be unusable in that specific situation.
EDIT: And I picked up Zahara hair, since Wild Waves was going to be unusable in backlighting situations ... and it has exactly the same issue. I mean ... EXACTLY the same issue, the whole hard half-halo thing. (I expect the fact that it's only a half halo has more to do with the light position than that transmaps, actually.) It also had a full color transmap -- although this one did have gamma at 1.0 -- so I saved it out as true grayscale, and it did just as much with Zahara as it did with Wild Waves, which is nothing. Apparently, heavily transmapped hair is just going to be like that.
The other thing to try...generate a new transmap in an image editing program, like Photoshop or GIMP.
Unfortunately, I don't have any idea how to do that. The transmaps for Zahara and Wild Waves don't apper to be derived from the diffuse, the way bump and displacement can be. And even if I knew how to make them properly, I'm not sure what difference it would make. For Zahara, I saved the file as grayscale, with gamma 1.0 and with a new file name, so that Studio would be forced to load a new file, and it didn't seem to work.
Thanks for trying to help.
I haven't found the fix either, so for now I'm going to have to just use different lighting and continue on. Thanks for the assist as well!
OK I don't have Slosh UHT hair shaders for Iray so I will need a screenshot of your Iray material settings. I am rendering a pic now that has a spot for backlight and don't get this issue. Translucency is set to 40% with the diffuse map in the Translucency Colour slot
Ok- I'll have to do that later, must get ready for work. Thank you!
You are not alone ... http://www.daz3d.com/forums/discussion/comment/850661/#Comment_850661
Did you try same scene with another transmapped hair? Did you try with simple backlight?
As I read the other thread where explain similar problem, there used the painter lights - so I think the light cause this. This is an Iray thing as I read.Try to set translucency to zero or move the backlight, make it smaller or use point light.
The shaders don't actually matter. I've tried with Slosh's shaders, with OOT's Iray Pair shaders, and with the default DAZ Iray Uber shaders, and it occurs with all of them.
Translucency on my tests was set to 100%, per the settings for the item. I also tested with translucency at 0%, once I realized that the transmap was the issue, and the effect was still there. It seems to be something about the mere existence of the transmap.
Details on everything I tried are at http://vwrangler.deviantart.com/art/Wild-Waves-and-Zahara-vs-Backlight-revised-558891862
The part I don't understand is why it's directional. You'd think a transmap issue would be visible with strong lighting from any angle, if that's the issue, but it's only backlighting that causes it.
Looking at how things are setup, it may require the light to be slightly above as well as behind the hair, and relatively strong and close. Beyond that ... I got nothin'.
I didn't realize that the edge of the light was the issue, although I was pretty sure it was about the positioning. Maybe that's why the transmap halo on my images has such a straight bottom edge.
well I have tried 3 hair products from http://www.daz3d.com/3dream and never had this issue.
Apparently they do something different with their transmaps, then. The three hairs in this thread are Ancient Combat (I think - Daz Original/Neftis), Wild Waves (Outoftouch, from elsewhere), and Zahara (3D-GHDesign, recently on sale here).
And speaking of 3Dream and Mairy hairs ... meet Perseus Hair in the attached image. Less emphatic because the hair itself is smaller, but still quite definitely present. Same lighting setup as before.
That said, I've run into one thing that's ... odd. Well, more odd, anyway. I noticed that the back light for that particular Painters Light setup wasn't actually aimed at her head -- it was aimed through the middle of her body, and slightly off to one side. So I aimed it at her head directly, put Zahara back on, and tried again, figuring that that the transmap halo would still be there, but it would cover her entire head where the hair was, and not just the top half. And ... nothing changed. I mean, yes, there was more light on her head, but the halo was still only half the hair and not the whole thing.
Weird. Definitely weird.
This is what happen whenever an Iray light is set to one of the shapes instead of point, they show up through transparent items.
Yeah I was just coming to say that too. I did some testing and found the same thing. This image I used a distant light as the back light, set to 50 lumens
Yes! Thank you both, that fixed the issue. You still have to be careful about intensity -- since the rim lighting effect was killed when the light changed to point from rectangle, I increased it from 12,000 to 20,000, and that actually showed the skull cap through the hair. Interesting look, that, but maybe not a good one. At 16,000, there's at least some of the rim lighting, without either the transmap or skull cap showing.
Thanks again for figuring out what the issue was.