Alpha blending faces layered close to each other display in the incorrect order #742

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opened 2026-10-13 01:47:31 +00:00 by Hemiva · 2 comments

Hemiva commented

2026-10-13 01:47:31 +00:00

Environment

Slipstream Beta 1.3.0.8 (64bit) (SSE4_2)
Microsoft Windows 11 64-bit (Build 22621.4317)

Description

The viewer seems to be having trouble with rendering alpha blending faces that are very close together, like the eyes of the OpenPony avatar. In this case, the different layers of the eye (iris, shade, highlight, pupil, eye shine) are being layered in the wrong order, causing it to look very different from how it's intended to look.

The attached image contains a comparison between what the OpenPony eye of the model used usually looks like (taken on Firestorm, but previous builds of Slipstream also displayed the eyes that way), and the way the Beta 1.3.0.8 build renders them.

The attached video also demonstrates another symptom of the problem: if you look closely enough, you can notice that part of the pupil briefly clips through the eyelids during the eye closing animation.

Reproduction steps

To make an OpenPony model with which the bug could be visible, you have to use the [OP] OpenPony Full Customization HUD, press the button featuring an eye with a + symbol to go to the eye customization window, and apply any eye from there that uses all 6 of the layers given as options. The image attached in these reproduction steps demonstrates what was used in the examples in the description.

### Environment Slipstream Beta 1.3.0.8 (64bit) (SSE4_2) Microsoft Windows 11 64-bit (Build 22621.4317) ### Description The viewer seems to be having trouble with rendering alpha blending faces that are very close together, like the eyes of the _OpenPony_ avatar. In this case, the different layers of the eye (iris, shade, highlight, pupil, eye shine) are being layered in the wrong order, causing it to look very different from how it's intended to look. The attached image contains a comparison between what the _OpenPony_ eye of the model used usually looks like (taken on Firestorm, but previous builds of Slipstream also displayed the eyes that way), and the way the **Beta 1.3.0.8** build renders them. The attached video also demonstrates another symptom of the problem: if you look closely enough, you can notice that part of the pupil briefly clips through the eyelids during the eye closing animation. ### Reproduction steps To make an _OpenPony_ model with which the bug could be visible, you have to use the _[OP] OpenPony Full Customization HUD_, press the button featuring an eye with a + symbol to go to the eye customization window, and apply any eye from there that uses all 6 of the layers given as options. The image attached in these reproduction steps demonstrates what was used in the examples in the description.

SlipstreamViewer_lEP3KGe2ZM.mp4

1.1 MiB

comparison.png

1.9 MiB

eye hud.png

425 KiB

Hemiva added the

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2026-10-13 01:47:31 +00:00

Hemiva added this to the Slipstream project

2026-10-13 01:47:31 +00:00

sky_line commented

2026-10-14 06:46:52 +00:00

Owner

Thanks for the detailed report and the comparison screenshots! The cause was a see-through layer tolerance added in Beta 8 (for road decals) that was also applied to avatars: eye layers only millimetres apart (iris, shade, pupil, highlight) could all draw over each other, so the pupil got washed out. Avatars now use the exact depth test again, and in our testing the eye layers draw in the right order on a pony avatar. The fix will be in 1.3.0 Beta 10 -- please try it when that releases and let us know if you still see it.

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2026-10-14 06:46:52 +00:00

sky_line referenced this issue from a commit

2026-10-15 03:16:15 +00:00

Avatar alpha keeps the exact depth test; #731 tolerance is world-only (Refs #742, Refs #750)

sky_line commented

2026-10-15 03:32:49 +00:00