webgl_loader_ldraw.html has strange "black piece".

[linbingquan]

Describe the bug

In #22957 see strange "black piece" like screenshot. I am not sure it is bug.

To Reproduce

Steps to reproduce the behavior:

1. Run git reset --hard 2a3e413f93dbedd431718aa0943bad0074df9005 in CMD.
2. Open http://localhost:8080/examples/#webgl_loader_ldraw in Browser.
3. See strange "black piece" like screenshot.

Screenshots

Platform:

• Device: [Desktop]
• OS: [Windows11]
• Browser: [Chrome96, Edge96]
• Three.js version: [dev LDrawLoader: Fail gracefully if an object could not be loaded, improve file compatibility #22957]

[Mugen87]

BTW: On dev the progress bar looks like so:

It looks fine in prod. Seems the calculation broke at some point in this dev cycle.

[Mugen87]

I can't see the mentioned dark pieces on dev using Chrome on macOS:

https://raw.githack.com/mrdoob/three.js/dev/examples/webgl_loader_ldraw.html

[gero3]

BTW: On dev the progress bar looks like so:

It looks fine in prod. Seems the calculation broke at some point in this dev cycle.

It is just githack that sends the mpd file in gzip compression while threejs.org doesn't send it compressed. The calculation stayed the same.

[mrdoob]

@Mugen87

I can't see the mentioned dark pieces on dev using Chrome on macOS:

https://raw.githack.com/mrdoob/three.js/dev/examples/webgl_loader_ldraw.html

I can in Chrome on macOS 🤔

[gkjohnson]

I see this too -- looks like it's related to normal smoothing because it disappears when you disable that setting.

Edit: r135 doesn't seem to have the issue:

https://raw.githack.com/mrdoob/three.js/r135/examples/webgl_loader_ldraw.html

I'll have to look at the changes that I made in r136...

Edit: It seems that #22957 caused the issue since the commit right before (03423cf) does not have it. It's not clear from looking at the code what might have caused it, though.