I’m currently working on UE 5.7.4 to render a logo for a client, I won’t be able to post screenshots of the actual logo as I’m not allowed to share it anywhere, but the issue is quite simple :
I want to render the logo with a transparent background, which works perfectly, except for the emissive, the background is transparent, the logo isn’t, but it looks like the emisssive isn’t even rendered.
what’s the alpha output? is it sharp edge? this seems like the same issue the blender compositor is producing. bloom does not influence the alpha channel. it’s only applied to the diffuse color. so you would have to blur or “bloom” the alpha channel seperately.
descriptive pictures. it’s not ue, but… you get the gist?
Thanks for your answer, what do you mean by “what’s the alpha output? is it sharp edge?” ? Thats not really familiar to me, I’m just using an empty Unreal scene with the logo I want to render and some lights to make it look it right, and in the movie render queue I ask it to render it with alpha so the background is transparent. Which works great, except for the emissive & glow that isn’t captured into the alpha I guess.
I tried compositing it in Photoshop with 2 renders, one being the logo only without the emissive/glow on a transparent background, and the other being the logo WITH emissive/glow but on a black background, and then with the Linear Dodge (Add) in photoshop it works, but it doesn’t look like I can export that to a .PNG sadly.
@glitchered is likely correct here. Bloom, the haze around the actor, is not represented in the alpha channel. And the default windows image viewer premultiplies the alpha when you look at it.
I would try another viewer and see if its there. If you need an alpha channel with the bloom just change the emissive material to white and then you can change the color in PS or Nuke or something.
Hi Shaun, thanks for your message, I’m not using the default image viewer, but ImageGlass, which is an open source viewer that seems to work very well, I also got IrfanView and on both these viewers the renders look the same, no bloom whatsoever when rendering with transparent background.
I followed your advice and changed my emissive to 100% white then rendered again, but I still don’t have any bloom in my render .
Is there anything else that I could try ? Maybe there’s a way to actually convert that fusion mask (Linear Dodge - Add) from photoshop that actually worked into a transparent .PNG ?
Anyway thanks again and have a wonderful week-end !
i reckon shaun meant to say you render the glow in white and copy that secondary output into the alpha channel or layer mask or whatever it’s called in PS.
Oh okay yea I tried that, that kinda works but it still doesn’t look as good as it does in my scene
Do you guys know if theres any way to actually get the bloom to still render in the alpha ? Like with a post-process material added to the movie render queue settings or something.
Yes I can also see it in the RGB, but when rendering with an opaque background only.
When I render with a transparent background, and enabling the alpha in MRQ, the bloom from the emissive isn’t rendered anymore.
I understand. The bloom part of the render will not be in the alpha. My guess is that you are viewing the image with a viewer that will automatically premultiply the image against the alpha so its chopping it out before displaying it to you. Can you share the raw image you are producing?
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