Outline over composite when using glare postprocessing Tweet

[Yngvai]

I'm compositing a robot into live action footage, and I wanted to simulate some of the glare from the sun off the metal of the robot. I'm using Octane glare post-processing in Blender.

If I render the robot as alpha channel and bring into After Effects as straight/unmatted, I get a nice clean matte, but glare will only show up on the robot and you won't see any glow, bloom, or glare against the background.



However, if I bring in a second layer of the robot as straight/unmatted, invert the alpha channel, change the blending mode for the layer to "add", then I'll get a bit of glare spilling into the background as I would want (note the glare spilling towards the back off the metal off the foot to the left). However, I also get a white/yellowish outline around the robot.



I can add a matte choker to the 2nd glare layer, but this ends up producing a small dark gap between the spillover glare and the glare on the robot.

Any way to fix this?

[Yngvai]

For further info, here's how it looks in the render viewer as it's rendering.



Here's how the inverse alpha looks in After Effects. You can see the outline around the whole robot. This is with glare and bloom both set at 0.1, glare blur set at 0.20, glare rays at 8, and glare angle at 0.15.



Even when I reduce the glare and bloom further to 0.01 each, the outline is still there. Increasing the cutoff value also doesn't help.



It's that outline around the robot that's causing problems, and I don't know how to get rid of it, other than the After Effects matte choker which then introduces a gap between the glare and the edge of the robot foot.

[elsksa]

The answer is right here. viewtopic.php?f=32&t=82062&p=426645#p426645 This may not be a step by step guide but is the solution. Properly encoding “alpha” as EXR and properly setting it up in post is all that’s necessary. No tricks or workarounds, that'd be red flags. For reference: EXR file format.

[Yngvai]

The answer is right here. viewtopic.php?f=32&t=82062&p=426645#p426645 This may not be a step by step guide but is the solution. Properly encoding “alpha” as EXR and properly setting it up in post is all that’s necessary. No tricks or workarounds, that'd be red flags. For reference: EXR file format.

I must be doing something wrong somewhere though, because using premultiplied alpha/EXR doesn't seem to work. In the post you linked to, I still got the white line around the car even if I checked "premultiplied alpha" in the Blender Octane Render output settings (outputting as openEXR), and also input it into AE with premultiplied alpha.

And in this case, if I check "premultiplied alpha" in Blender Octane Render output settings, and then bring into AE, I completely lose the post-processing around the robot and only have the alpha channel for the robot.

Unless there's a setting or step I'm missing somewhere.

Here's my output settings for Octane in Blender:



Then when I import it into AE and then hit "Interpret Footage", I leave premultiplied checked.



But when I bring in the EXR again for the added post-processing effect (and choose "ignore" in AE so I can get the additive glare from around the robot), it just shows the robot surrounded by black...there is no additive glare around the robot (there was if I didn't choose premultiplied during render process, but then I have the outline problem as noted before).