Render layers at different resolutions?

One thing cycles struggles with is glitter/glints

When the glitter is around pixel size or smaller, the glints often get missed by the compositor glare node because the compositor node work in screen space on the final image.

I had an idea on how to fix this (kinda). My idea is to render the scene in two passes.

The first pass would be at twice the resolution of the final image, but rendered with very low samples. I would then apply the glare compositor node to this to pick up the tiny glints. I would then reduce the resolution of this glint pass by half.

I would then render the actual scene at the final lower resolution, and composite the glint pass over it.

I have figured out how to apply the glare and reduce the resolution of the glint pass - but i’m having difficulty automating this with the final render pass. Is there any way create render layers at different resolutions?

Have you tried this?

The only downside is that you have to run it from the command line, but I think it would help you out. Every scene can have its own settings. Is is quite powerful.

Thanks - I might give it a try, although rendering separately and just loading into compositor is probably easier for the few scenes I might use this.

Instead, you could try dilating the problem areas to increase their prominence for the glare node.

How do you mean?

Check out the attached example.

dilate_glare.blend (549.3 KB)

Thanks - looks promising.