Minor transparency error on certain distance.

[adfriz]

Description

as title said.

Reproduction

Load Fujikyu train in object viewer, the 6501.animated, move the camera to that coordinates.

From what i test, there is 2 visible bug:

1. outlines on transparent image
2. some window transparency got discarded ?

outline bug only shows if we use any texture filtering except nearest neighbor ones.

Route

no route

Train

https://charlesindobve.yolasite.com/japanese-railways.php

Logs

no crash no logs

Related information

• Operating system: win 11
• Tested on OpenBVE 1.13.0.8 and latest master and pr Update Net Framework version to 4.8 #1364

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I suspect both alpha sorting and texture filtering maybe the cause.
Haven't tried in the main game but i can assume it may affected too.

[adfriz]

i feel this bug may already occurred way before 1.13...

[leezer3]

It'll probably be in every build back to the beginning.

I would suspect this is probably a power of 2 issue- The offending texture (rear2.bmp) is 192x192

[leezer3]

Having tested, there's no ringing here.
Nvidia 3060, Windows 11.

This makes it smell even more like a power of 2 issue.

The sides being funky looks like an artifact of the way it's been built, combined with the painters algorithm.

TLDR:
The sides are made up of 3 faces.
Outer, at 1.4- color key transparency
Window glass at 1.39- solid semi-transparent face
Inner at 1.37- color key transparency

Viewing a semi-transparent face through multiple layers of transparency never ends too well with the painters algorithm.

[adfriz]

seems nothing we can do about it for now?

[leezer3]

Without throwing out the Painters algorithm for something else using proper depth sorting I don't think so.

[adfriz]

from quick search it seems plenty of transparency method like OIT or weighted blended variants...

https://learnopengl.com/Guest-Articles/2020/OIT/Introduction

it looks pretty hard to understand.