Rendering with transparent PNG doesn't render the bloom-effects

Hi there folks,

I’m trying to create a animation in Blender 2.8 in Eevee. When exporting to transparent PNG’s it doesn’t render the bloom I’ve setup. See the image…

Is there something I can do to change this, thanks!

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I would like to know if there’s any workaround for this problem as well.

Right now there isn’t. It is because render results use premultiplied alpha. I also want to expose the non-premultiplied render result. I will see with other devs what’s the best approach.


Haven’t tried with Eevee, but I’m guessing it’s the same as cycles. The glow is still there but it doesn’t show up in the image viewer because of how blenders viewer handles alpha, as hypersomniac mentioned. If you save out the file and do an alpha over operation, you should be able to see the glow, since the RGB values are there with a proper 0 alpha, meaning they get added to the RGB values of the other image.

You can see those values in blender using the non-premultiplied view available on the viewer toolbar, but you can’t see it properly unfortunately unless you go through the compositor and add a background image.

In short, if you do an alpha over to composite this on top of something else down the line, your glow should be visible. I do agree that a proper viewing mode should be added to the viewer to be able to see these effects there.

You could try compositing like the example I linked here. I split the rendered image in two nodes, blurred one and then mixed them together again. You can play with the blend modes if you want a slightly different effect and increase/decrease the blur with the x and y blur factors (amount is in pixels I believe)

Here is a link to the file.

Not the way to go. As @Hypersomniac mentioned, it´s about the alpha premult.
On your image, internal edges are blown out (washed out, destruction of information)…
Catastrophe to composite. A multicolored cube is nothing to worry about.

Think what would happen on a far away building with windows glazing from a sunset view, to see what a nightmare it will become to recover detail information and have the bloom working correctly…

It’s not perfect but a workaround as asked. Better than nothing in my opinion. Some tweaking with the values of the blur and the blend modes may give a better result.


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