Hi. I am following the CGboost work course on landscapes. The scene has a view layer workflow in which each natural element is rendered separately to be composed in Blender.
I am importing EXR files into Davinci and converting each layer into the AGX view transform via a LUT I bought. But I get the white edges around layers:
I checked, and it says “pre-multiplied”, so I am unsure what to do. I checked in PS and also got the white borders.
What can I do to fix this?
Thank you
The problem occurs when the background of the layer is not pure black. The solution is to render with a black background, even if it is rendered as transparent.
I am not sure I follow. The scene has an HDR, and I am using the transparent feature.
Where exactly should I set it to black to get this to work? Would you be able to share a screengrab of what you mean?
Thank you
The background only needs to be black for the camera rays. To do this, in the World shading node editor, use a color mix node controlled by a Light Path’s Is Camera Ray. The HDRI goes to the top socket and the bottom socket is set to black.
I will try this out; I have to admit I have never heard of such a workaround in other 3d software. But I guess it is what it is.
Same for me. I ran into the same problem a few years ago and, after some experimenting, I came up with this solution. I found it weird at first but I accepted it because it just works.
Why are you writing log EXRs? EXR, as a format, really wants to hold linear data.
You want to stay in linear if you’re going to be compositing anything. Converting the image to log will break the relationship between RGB and alpha (note how the curves are no longer the same shape), which can definitely lead to issues like glowing or dark edges.
Render in linear, export in linear, composite in linear, then convert to log and apply your desired output, like AgX.
Hi, I honestly ignore colour management. My expertise is in modelling and rendering, not the colourspace, so I do things that I do not know by following people who instruct me how to do so. I set the file outputs as they are based on this guy:
If you check at 2:00 min, he says, “I like to use…Agx log”
So, coming back to the right approach, there are several “linear…” I would highly appreciate it if you could please share with more precision which one I should use.
Thank you
Yeah, I’m not really sure what he’s doing there—it’s fine to render in log if you want, but if you’re going to do that you should use a format meant for log, like TIFF or DPX or PNG. EXR is really best suited for linear data, and will potentially lose precision if you use it to store log data. (He also talks about the log output as though it preserves more detail than a linear EXR—while log holds more information than the default view-transformed AgX or Filmic output, it holds much less information than an actual scene-referred EXR.) Notice also that he’s rendering a single image for final grading, not a bunch of layers that still need further compositing—that’s where you really want to stay in linear.
If you just let the color management handle itself, instead of Overriding in the export dialog, your EXRs will be the correct linear (specifically, the rendering space, which in Blender 4.0 is linear Rec.709).
In Resolve, you can use Troy Sobotka’s AgX DCTL, which will let you apply AgX with the bonus of tweakable parameters for highlight rolloff and hue shifts, or you could load the AgX config in Fusion and apply a log transform there, which would let you do your composite, transform to log, and then grade in log with that LUT on top, as shown in that video. You could also do both transforms in Fusion, but since Fusion operations happen before color grading, you’ll be doing a little two-step where your clip gets transformed to log, then graded, then wrapped into a Compound Clip so it gets another Fusion tab, where you can convert from log to display (sRGB, Rec.2020, whatever).
Thank you! I will try the LUT from Troy. I also noticed 4.1 and 4 export different outcomes. In 4.1 I do not get the white borders.
