Reproduction Steps
Reproduction place: viewportbug2.rbxl (35.0 KB)
When changing background color, you can see that the border of the part is changing color, even though the BackgroundTransparency of the ViewportFrame is 1
It gets more egregious when the part itself has more transparency:
Expected Behavior
The part should look the same no-matter the BackgroundColor of the ViewportFrame when BackgroundTransparency is 1
Actual Behavior
BackgroundColor creates a border around objects within a ViewportFrame when the object is opaque.
The entire part turns into the BackgroundColor when transparent, which makes transparency in ViewportFrames especially difficult.
Issue Area: Engine
Issue Type: Display
Impact: High
Frequency: Constantly
3 Likes
Woops, the title has a typo, it should instead say:
‘Objects inside ViewportFrames have colored borders when BackgroundTransparency is 1, causing poor visuals’
Sorry about that!~
Thank you Hooksmith for changing the title 
2 Likes
This has been an issue for a long time, I wasnt aware of the problem with part transparency though.
You should probably use ViewportFrame.ImageTransparency instead of Part.Transparency if possible
1 Like
That’s a good workaround for some use cases, although it wouldn’t work for ours
We’ve been trying to upgrade our UI by using ViewportFrames for certain elements, but the ugly borders demonstrated by the first GIF completely prevent us from moving forward with our upgrades
1 Like
Hello. Thanks for the report. Filed an internal ticket.
2 Likes
As a bump, viewport background color also affects any decal with an opacity less than 100%, when the part it is parented to is transparent, even when the background transparency of the viewport frame is 1
(I don’t know if this should be a new post or not)
