How do I get bloom to render in a transparent image? Tweet

[amysterling]

I have been having trouble getting bloom power to show up in my renders. It shows up if I include a backgound in the render, but I can't seem to get it to appear on any transparent image. Does anyone have ideas as to how to fix this? Here is an example of bloom with bg vs without (same render, no setings changed except to render alpha) I have tried every variant I can think of, including multilayer files.

It may be worth noting that the blur shows up in picture viewer, but when I bring the image into .ai it is gone.

Here is the project file in case anyone is willing to help. https://drive.google.com/file/d/1xU6S6P ... sp=sharing

Thank you
Amy

[bepeg4d]

Hi,
the issue is that the Alpha channel is cutting the pixels for Bloom/Glare.
The workaround is to render with Alpha Channel active, but without Post-Effect.
Then set the Kernel to Max Samples = 32, and render again the scene, saving only the Post Effect pass, with Alpha Channel disabled.
In this way, you can compose the Post Effect pass in Linear/Add mode in post.

ciao Beppe

[amysterling]

Thank you for the analysis. I have not ever rendered out multiple passes -- do you happen to have a tutorial on this?

Is there any way to make the alpha catch the bloom? That way I do not have to add another step to the render process plus keep up with 2 files for every cortex render, of which I have so many already!

[aoktar]

It's not designed as you liked. Bloom effect is obtained by normal blend. Probably screen blending or so. Because of this it's useless to wish it in alpha. There's a Post renderpass. You should use it in post.

[adamwhatelse]

Yes, had the same situation right now, and what aoktar wrote works perfectly! In the Render-Settings activate Post-Processing in the Render AOV Groups!

[boxfx]

There's another method which avoids extra files. If youre making an animation then just import the footage into after effects twice, once with interpretation set to use the alpha and once with it disabled. The glow data is in the colour channel of the render, the alpha channel is just cutting it away. You can stack the version with no alpha behind with mix mode set to add. This way you get your main crisp top render with alpha channel plus an un-cut version below acting as the glow.

The same is possible in PS but theres more steps involved.

[elsksa]

Here’s how: EXR. There is a gif demo in a section on this page.

[boxfx]

Can you elaborate? No combination of exr settings causes the glow to render into any of my exr exports outside of rendering a post effect pass, but then that works on all file formats.

[elsksa]

What is demonstrated on the .gif and explained on the page is simply a quick EXR export of the beauty (no AOVs aka Passes) from Standalone. The EXR compression type isn’t relevant.

The key info is in the title of the file nodes from the compositor, shown in the gif, explicitly pointing towards the indisputable advantage and necessity of EXR.

Let me know if any further clarification are needed.

[boxfx]

Further clarification is needed.

The problem OP has is that when you export a beauty pass with alpha channel, the octane post glow is cut away by the alpha channel. Changing the export format between png, exr, tiff or anything else doesn't change this fact. Unless you would like to demonstrate otherwise