Incorrect Rendering For Intersecting Transparent Parts

Reproduction Steps
When two or more base parts with a transparency value greater than 0 intersect or are viewed through each other, the engine is unable to correctly render one on top of the other. This is most evident when the parts are intersecting, but also occurs at narrower viewing angles when viewed through each other. When this does occur, the parts flicker in transparency values as the engine struggles to decide whether it is in front or behind the other part.

Reproduction Files: Rendering Bug [Uncopylocked] - Roblox

System Information: 11th Gen Intel(R) Core™ i7 @ 2.50GHz, 16.0 GB, NVIDIA GeForce RTX 2060
This also occurred on an older computer that I no longer have the information for.

Expected Behavior
Base part with transparency value greater than 0 properly changes its transparency value when viewed through another transparent base part with a transparency value greater than 0.

Actual Behavior

To break this video down, the first row of examples show how intersecting base parts with a transparency value greater than 0 interact with an opaque part. For the most part, these behave as expected, but you can see that the surface gui renders incorrectly and the text label appears on top of the green part (unexpected behavior) when it intersects and behind the green part (expected behavior) when not intersecting.

The second row of examples demonstrate intersecting base parts when all have transparency values greater than 0. The parts constantly appear in front, behind, and entirely disappear.

The last row of examples shows how base parts with a transparency value greater than 0 interact when not intersecting. As you can see, the yellow mesh part flickers; however, I was only able to replicate the green part doing it on the first part. To clarify, the green part did have the same issue when testing before recording. It is just a very narrow angle that it occurs at.

Issue Area: Engine
Issue Type: Display
Impact: High
Frequency: Constantly
Date Last Experienced: 2022-02-09 00:02:00 (-05:00)

4 Likes

Unfortunately this is very difficult to properly fix due to how the object sorting has to work for proper blending. Since roblox uses rasterization it’s very difficult to handle transparent objects correctly. I doubt this will get a proper fix for a while, if ever.

1 Like

That’s quite unfortunate. I’ve run into issues with this many times while building.

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I filed a ticket for it. Maybe the engineers can do something about it.

2 Likes

Hey everyone, just circling back here, as @qwertyexpert mentioned, this isn’t something we intend to fix. Apologies and huge thanks for the report.

1 Like