search

ValveSoftware / halflife

Half-Life 1 engine based games
Other
3.66k stars 616 forks source link

[Engine bug] Entities on moving platforms are not stable #586

Open UCyborg opened 11 years ago

UCyborg commented 11 years ago

This bug causes entities, most notably NPCs, to be "twitching" while on moving platforms (trams, elevators, ...). Since player is also just one of many entities in the game world, this also affects him/her, e.g. getting stuck while riding up on some platform in Xen.

I've recorded some videos to show bad effects of this bug: http://www.xfire.com/videos/5e646d http://www.xfire.com/videos/5e646e http://www.xfire.com/videos/5e6473

MrSchism commented 11 years ago

I haven't experienced this issue, however I have noticed that moving-platforms have a bit of a strange effect on physics. Jumping while riding the tram will more or less throw you to the back of it because your leap moves you vertically, ignoring the forward momentum of the tram. Essentially, you land in the same global spot you left the ground... which is now at the back of the tram.

UCyborg commented 11 years ago

Getting stuck on the tram is a bit tricky. I really can't give any precise instructions on how to reproduce it, other than just move around those corners in different manners and if you're lucky, tram will suddenly stop. I included that tram scene because I'm 100% sure it's caused by the same bug.

About throwing you at the back of the tram, as I understand, logic behind it is: while entity is standing on moving surface, move it along with the surface, otherwise don't (when you jump, you're not touching the ground anymore until you land).

Anyway, here's another scene with Vortigaunts from the singleplayer map c4a1e being displayed by two different engines, latest Half-Life 1.1.2.2 /Stdio 5964 and Xash3D build 2153: http://www.xfire.com/videos/5e696a

I think devs should look into how engine handles MOVETYPE_PUSH related stuff.

DanTheMan1 commented 11 years ago

Yeah, this also applies to cs/tfc/etc.