Bloom Multipass Tweet

[ajiblock]

Hi,
I have a particle simulation that is going to be weaving through a forest. The particles need a large amount of bloom. In my first test, I rendered the particles with bloom baked in and layered them over the photo, producing a very nice result (image 1). However, I need to rotoscope the particles, so some trees mask them out. I was unable to rotoscope the particles with the bloom baked in because you can see where the light of the particles gets cut out, since the bloomed illumination bleeds into the actual image (image 2). Next approach was to render two passes from octane, one bloom and one beauty, and then mask and composite in AE, however no matter what blend mode I try on the bloom pass (linear dodge, screen, add), i'm unable to get a similar result to my first test (image 3), the bloom is significantly weaker and lower quality. Any help would be hugely appreciated – assuming I might just have to do the bloom in post with something like Nuke, but would be great to be able to do it straight with Octane. Thanks!

[hausgross]

Since bloom is a post-effect I'd recommend you create it completely in AE using the internal glow or a plugin you like. You can have very fine control and it makes integration easier, because there will be no hard edges when you roto the tree. A realistic bloom bleeds around the edges of the object by which it is occluded, and it's hard to achieve a convincing falloff if the bloom is prerendered.

[bepeg4d]

Hi ajiblock,
please, try with this settings:

and with this xpresso to use your image in Visible Environment node:
viewtopic.php?f=87&t=63808
ciao beppe