[HL2] Vertices stretch toward world origin on specific citizen models

[Blixibon]

Describe the bug

The following models in Half-Life 2 have random vertices seemingly stretching to the map origin and other positions:

• models/humans/group01/male_02.mdl
• models/humans/group02/male_02.mdl
• models/humans/group03m/male_02.mdl
• models/humans/group03m/male_04.mdl
• models/humans/group03m/male_05.mdl

The issue becomes less intense as the LOD level increases (i.e. as the player gets farther away). This issue appears to exist in both HL2 and HL2:DM, although the models involved are not used in HL2:DM by default.

This is on the latest version of the Source 2013 master branch.

Steps to reproduce

Steps to reproduce the behavior:

1. Spawn an entity which uses one of the above models. The following command creates a prop_dynamic with the first listed model: prop_dynamic_create "humans/group01/male_02"
2. Walk around the model in close proximity
3. See vertices stretching toward the world origin

Media

Here is a short video demonstrating the issue:

https://github.com/user-attachments/assets/258e2181-d29e-461d-94de-8c9f7126b38a

[Blixibon]

After further investigation, the issue appears to be coming from the models' mouths. The issue stops occurring when r_teeth is disabled.

I also confirmed that this issue occurs with other users as well, although it does not appear to be present on Linux.

[misyltoad]

You might be able to get more info if you compile your own shader DLL containing teeth and play around with this.

But I will add this to my backlog of things to look at.