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Are those of you with halos lighting with HDRs and those without not?
I use distance canvasses a lot for cool post work (like VERY easy haze effects), and I've run into issues where the edges of a foreground item don't mesh in Distance canvas with the Beauty canvas. Maybe one is anti-aliased and the other isn't? I'm not sure.
But I've often had to do a bit of careful blur and adjustment of distance canvas to get things to play right.
All my examples were rendered with a DimensionTheory HDRI, no other lighting.
I setup with a single spotlight, scene only, and it was the same issue. I know that the eyes of the front character are creepy, not sure what happened but was only interested in the halo portion:
Yeah, looks like the same issue I have. Very curious that some people are not having this problem, I cannot avoid it when rendering with canvases.
Just to keep it simple, another example (this was going to tif). Two beauty passes. One of the spheres, one of the plane. Single spotlight. Then I added the hot pink background behind the two layers in photoshop because adding a black layer doesn't fix the problem, it just makes the space black which is less noticable.
I don't suppose anyone who doesn't have this issue would be able to demonstrate? The earlier example of a fix is just the figure, which won't show this issue, it's only when two objects in a canvas overlap and are exclusive between the canvases.
I get the same results in gimp, but honestly it's been so long since I've used gimp I wouldn't know where to start looking at additional... anything.
I'm not 100% sure that a black layer doesn't work in a way that actually eliminates the problem somehow because I can't see even a 1 pixel black edge around transparent hair. Maybe black interacts with TIF transparency in a way that it doesn't with any other formats?
I may begin to understand. I think you're having an issue because you don't composite correctely and you get a halo because of the transparent pixels around the object
Bottom Layer must be black. Then you add the layers in Linear Dodge 'add' mode in Photoshop. See http://blog.irayrender.com/post/76948894710/compositing-with-light-path-expressions
I am not sure what it is with a black background that is required in PS but it does the trick and as @Takeo.Kensei pointed out with the link, it is what the iray devs recommend/use for compositing in PS. I no longer have an active trial for Nuke or I would try in that to see if it has the same issue as PS or not. I suspect it is the editing software's handling of the layers that cause the need for the black background layer.
I guess the answer is just that this is a limitation and an expected result that needs to be worked around, which is fine I can live with that. At least I know others seem to be getting the same results so it isn't something I can expect to fix with other settings.
Huh, so it's basically what I said about 25 posts ago? ;) Thank you for confirming it, it's good to know.
It's a matter of logic. Principle is to add colors with successive layers. If you have a white backgrounf that won't do (white + any color = white). If you have a transparent background, there will be problems in areas where you don't have full opacity. Thus the black background solid color
The problem here is that you have overlapping transparent pixels with alpha channel (due to antialiasing) and the sum won't make a full opaque pixel
You can try to create alpha channel from materialID pass but that will look crappy unless you render at very high res
You can try Natron which is free and is a Nuke clone, or Blackmagic fusion if you need 3D features. Blender can also be used, even if lots of people don't like it
Thanks for the recommendation, I will try them out!
I've noticed odd behaviors with backdrops and HDRI when Iray first came out during testing of volumetrics. Strange behavior popped up again today when I was testing a product for a friend. This was rendered in Iray with an HDRI as the only lighting and a backdrop:
If you zoom in, you can clearly see how the portion of the model (red) in front of the black area of the backdrop appears to be aliased, while the portion of the model in front of the white area of the backdrop does not. The model's edge seems to be shifted and extended inward when in front of the white area of the backdrop.
This is also reminiscent of how Iray in DS renders transparent hair backlit by bright lights (jaggies).
I don't render much in Iray, but I figured I'd mention it in this thread FWIW.
- Greg
ETA: PNG was saved out of DS with no transparency (the backdrop was in DS, not added later in post).
I don't know if this helps but I gave up on png years ago. If I need an alpha I always save as tif out of Studio. When I bring it into PS the alpha is never wonky and already in a separate channel. If I want I can resave with compression (lzh) with PS to save some space.
I'm going to do that from now on Spit, now that I know there are actually real-world differences in how we work with them. Thanks.