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Blending/semitransparent alpha for TGA/PNG

I would like to use semitransparent/blending alpha in TGA (or PNG) pictures. When I import TGA(32bit) to UE4, the final quality of rendered picture is terrible. It's showed on screenshots:

In Photoshop - how it should look like ![In Photoshop - how it should look like][1]

in UE4 - texture editor ![in UE4 - texture editor][2]

in UE4 - sprite editor ![in UE4 - sprite editor][3]

in UE4 - editor render ![in UE4 - editor render][4]

As you can see, after import to UE4 in texture editor the alpha blending is ok, but picture is little bit compressed (why?), in sprite editor the alpha is without blending and final render is terrible. What should I do to fix it?


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asked Dec 04 '14 at 12:12 PM in Rendering

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3 answers: sort voted first

Hey thobias -

By Default the Sprites in Paper2D use a Masked Material, in order to get the smooth transition like you have in Photoshop you will need to use a Translucent Material, which is also provided in the Paper2D directories (MaterialInstanceConstant'/Paper2D/TranslucentUnlitSpriteMaterial.TranslucentUnlitSpriteMaterial')

Thank You

Eric Ketchum

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answered Dec 04 '14 at 03:11 PM

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Lovecraft_K ♦♦ STAFF
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avatar image thobias Dec 04 '14 at 03:36 PM

Thanks a lot, with that material blending alpha is much better, but still there is wired white outline. How can I fix that? Thx.

alt text

outline.png (326.8 kB)
avatar image Lovecraft_K ♦♦ STAFF Dec 04 '14 at 10:00 PM

Hey thobias -

This white edge is a product of a matted Alpha Channel. You will want to create an unmatted alpha channel in Photoshop or GIMP etc. Bill Kladis an FX Artist has posted a great tutorial about how to correctly make the alpha channel unmatted:


Thank You

Eric Ketchum

avatar image thobias Dec 09 '14 at 10:59 AM

Thank you, that is exactly what I needed.

avatar image thobias Dec 11 '14 at 09:04 AM

I exported TGA exactly as i is showed in great tutorial, but still there is small outline (I guess it's because of TranslucentUnlitSpriteMaterial, but not sure how fix it).

alt text alt text

Original file is here: https://drive.google.com/file/d/0B0uYVWhdF5DcUUFqRWY4ZmtoNXM/view?usp=sharing

Can someone check it and tell me if it is exported correctly?

Also there is strange compression. I mean that artefacts like high compressed jpg. Is it possible to turn it off. I want best quality that is possible to render (like 100% in original TGA file). Thanks.

avatar image Lovecraft_K ♦♦ STAFF Dec 11 '14 at 02:26 PM

Hey thobias -

All you need to do is go back to the original file before running the Unmasked Alpha action (hopefully you saved it in Photoshop like Mr. Kladis suggests) and take your alpha and cheat it inward by 1 to 2 pixels. This will get rid of most if not all of the lines. I marked on your TGA where I am getting this information you can see if you turn the Alpha channel on in Photoshop that the places you are seeing lines are also the places where the alpha doesn't do into the sprite enough.

TGA File

Thank You

Eric Ketchum

avatar image thobias Dec 09 '14 at 04:36 PM

Unfortunately there is another problem with TranslucentUnlitSpriteMaterial. It makes all materials with that setting blurry during moving camera in "play" mode. It not happen in editor camera or with different material (like default). Here is video example (focus on billboard letters at background - deleted video ). How fix that? What happening actually? PostProcess is off...


avatar image thobias Dec 11 '14 at 08:44 AM

Fixed by turning of "temporal AA" in "Project settings..." under "Rendering".

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I want to know, how you guys would export 2D semitransparent layers from PSD for import to UE4 (and have correct borders/alpha). Exporting TGA files (videotut here http://youtu.be/oh2WGL8hvPo from every PSD is time consuming. Also when I make edit of PSD, I have to re-export new TGA that have different positions ale re-import in UE4 make mess with whole scene.

There must be a simple way, how save PSD with correct alpha and imprort it in to UE4.

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answered Mar 20 '15 at 10:57 AM

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avatar image Lovecraft_K ♦♦ STAFF Mar 20 '15 at 02:00 PM

Hi thobias -

I know your new question is related to this one, but if you can could you post it as a new question. It will help with visibility and clarity on the Answerhub.

Thank You

Eric Ketchum

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