Dealing with transparent meshes and ID lines.

[aVersionOfReality]

Say I have a scene with two objects. One is mostly transparent and has line thickness 0. The other is using Object ID lines. How do I get it to not draw a line around the transparent object? I've tried the Opacity mask, but this doesn't seem to help here. I assume the problem is that it isn't transparent in the pre-pass where the ID masks are rendered? Is there an intended fix?

[pragma37]

Could you share a repro file?

[aVersionOfReality]

Thanks, I'll try to make sense of how Scene filter works.

This makes sense. For the depth as an AOV, do you mean using it to do something like a Z Combine?

[aVersionOfReality]

I setup Z combine and it works except that there's an area between the line art and background that gets colored based on the transparent layer, and a second pure black area that the transparent layer does not overlay.

This only happens with line art enabled. I assume this is because the lines are not in the Z depth passes, and that the solution would be to have the line filter also expand the Z? Here's the file again incase it isn't that.

line_id_test-2.zip

[pragma37]

While the LineRender node doesn't output the line depth, the (internal) line_expand shader function that the node uses does.
So you can use that directly inside a ScreenPass and output the depth from there:

malt-line-depth.zip

[aVersionOfReality]

Alright I have set this up and it is working so far. But I cannot complete the setup because Pixel Depth does not seem to be working correctly. I was using the Camera Data Z Depth previously because Pixel Depth seems to just output a single value (.998...). Am I missing something in how to use it, or does this mean something else in wrong in my setup? This was the case in the previous files I posted as well.

[pragma37]

Forgot to answer, sorry!
The Pixel Depth and the Line Expand depth is in NDC (0 to 1).
If you want to convert it to linear depth you can use the Depth to Z node (this is an internal function, so you need to enable the Show Internal Nodes settings).