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Half-Life Hitbox Bug

An extensive post on the Natural Selection Forums offers details on a bug they've been battling that turns out to be present in the Half-Life source, rather than their mod. The problem seems connected to client prediction where the final player on a full server (i.e., player 10 on a 10-player server) is difficult to hit because the visible character on screen is not in the same location as his hitbox. They have determined that this problem is present in other (perhaps all) Half-Life mods, though it is not clear if it appears in unmodified multiplayer games. The issue also seems more evident the faster the bugged player is moving, which may be why it was more obvious in Natural Selection games.

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40. Re: HL2 Hitboxes Jul 26, 2004, 00:08 m00t
 
hitboxes are 3d constructs that envelope the extents of the model they are bounding. When you fire a hitscan weapon it draws a ray from the weapon's origin outwards and then does hit tests against hitboxes and the world.

The hitboxes (i think) are probably not going to be used for the final say as to whether something was hit. They are there to allow for an early out. If it hits the hit box it moves to the next step of determining which polygon(s) on the model the shot hit and where the decal should be placed if appropriate.

Hit boxes are always slightly larger than the model (or in some games, greatly... *coughCScough*). Some are static, some can grow dynamically with the model. They're updated every time the animation changes.

If you were dynamically updating hit boxes (say you had a deformable mesh on a creature) you would take the min/max x,y,z values from all vertices that make up that creature and use that to build the hit box (which requires only 2 vertices to generate. Min(x,y,z) of the model and Max(x,y,z) of the model. The other 4 points can be generated using combinations of those 6 values). This tends to be computationally prohibitive if there is a large number of deformable objects in the scene which is why you tend not to see it at all. The coolness factor of dynamic deformations is generally overcome by the easier method of precalculating the the hitboxes for each animation key frame and interoplating between them to smooth things out.

 
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  2. Jul 25, 11:22  Re: That's not nice... Tim1_2
  3. Jul 25, 11:47   Re: That's not nice... MeatForce
  4. Jul 25, 11:48    Re: That's not nice... Taulin
  5. Jul 25, 11:54     Talk about desperate JosephBlowski
  6. Jul 25, 12:31      Re: Talk about desperate JediLuke
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  37. Jul 25, 21:04          Re: Talk about desperate pob
  10. Jul 25, 13:43      Re: Talk about desperate BicycleRepairMan
  15. Jul 25, 14:22   Re: That's not nice... born2expire
  17. Jul 25, 14:33  Re: That's not nice... Satertek
  11. Jul 25, 13:52 No subject osmium
  12. Jul 25, 14:01  Re: No subject OsinO
  18. Jul 25, 14:42   HL2 Hitboxes Satertek
  38. Jul 25, 23:08    Re: HL2 Hitboxes Sepharo
  39. Jul 25, 23:19     Re: HL2 Hitboxes Sixis
>> 40. Jul 26, 00:08      Re: HL2 Hitboxes m00t
  24. Jul 25, 16:40   Re: No subject ildon
  25. Jul 25, 16:43    Re: No subject ildon
  27. Jul 25, 17:58     Re: No subject m00t
  33. Jul 25, 20:24    Re: No subject Chipper
  13. Jul 25, 14:07  Re: No subject BicycleRepairMan
  14. Jul 25, 14:12 No subject beigemore
  16. Jul 25, 14:23  Re: No subject Panick
  19. Jul 25, 14:47 hitboxes m00t
  20. Jul 25, 15:05  Re: hitboxes BicycleRepairMan
  21. Jul 25, 15:08   Re: hitboxes m00t
  22. Jul 25, 15:39 No subject Tanto Edge
  23. Jul 25, 16:28  Re: No subject Fillem
  36. Jul 25, 20:50 I know that bug very well Muscular Beaver
  41. Jul 26, 00:55 Amazing Overon
  42. Jul 26, 01:03  Re: Amazing Stolk
  43. Jul 26, 01:25   Re: Amazing Vek
  45. Jul 26, 01:42    Re: Amazing Stolk
  50. Jul 26, 08:41    Re: Amazing RegularX
  60. Jul 26, 16:06     Re: Amazing Sepharo
  46. Jul 26, 01:52  Re: Amazing Kris Redbeard
  44. Jul 26, 01:30 No subject Acleacius
  47. Jul 26, 05:36 Sorry NickX
  48. Jul 26, 08:30  Re: Sorry Isus_in_Black.
  59. Jul 26, 14:50   Re: Sorry Erratic
  49. Jul 26, 08:41 No subject Two_Sheds
  51. Jul 26, 08:53 Valve is teaming up with Derek Smart B M
  52. Jul 26, 09:06 Doom3 Hit detection TaggeD
  53. Jul 26, 09:50  Re: Doom3 Hit detection Mr Gar
  54. Jul 26, 09:56   Re: Doom3 Hit detection MeatForce
  55. Jul 26, 10:00    Re: Doom3 Hit detection Sixis
  56. Jul 26, 10:18     Re: Doom3 Hit detection MeatForce
  57. Jul 26, 11:44      Re: Doom3 Hit detection Sixis
  58. Jul 26, 13:31     Re: Doom3 Hit detection Yakumo


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