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Weird issues with LightningDamage()

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Orion Joined: 12 Jan 2007 Posts: 413 Location: Brazil |

Posted: Fri Feb 05, 2010 12:19 am Post subject: Weird issues with LightningDamage() |

Hi people, I always asked myself why the hell does the lightning gun checks for damageable entities in a different way not like the axe or the shotguns. On an attempt to figure out what LightningDamage() does, I put a TE_LIGHTNING2 effect on each traceline() of that function. I have some screenshots.
The result was lightnings coming from the wall, or from yourself but pointing to the sides, or even backwards!
When I saw that phenomenon, I thought 'WTF?!? Was that Id's FAIL attempt on making the lightning gun a shoot-through weapon, or even a hitscan weapon that the lightning ricochets walls?'
For me the LG is meant to be a simple hitscan weapon, no shoot-throughs like q2 railgun, nor "reflecting" lightnings on walls.
I alwas replace that LightningDamage() line to this:

Code:
if (trace_ent.takedamage) { particle (trace_endpos, '0 0 100', 225, 120); T_Damage (trace_ent, self, self, 30); }

Real simple. No more than 5 lines of code.
See the screenshots:
http://img231.imageshack.us/gal.php?g=wtf4.jpg
If you see the screenshots, you'll notice that any entity between these flying lightning beams *will* get damaged! I also get myself caught damaging 2 monsters at the same time. (w/o this modification).
_________________
There's no signature here. Stop looking for one.

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Spike Joined: 05 Nov 2004 Posts: 944 Location: UK |

Posted: Fri Feb 05, 2010 12:44 am Post subject: |

due to trace_ent / other mixups in the quakeworld qc code, when you stand on the secret door on dm6 then shoot it, the door goes flying upwards! great fun... and fundamentally fubar. _________________ What's a signature?

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Lardarse Joined: 05 Nov 2005 Posts: 243 Location: Bristol, UK |

Posted: Fri Feb 05, 2010 12:52 pm Post subject: |

This is both an issue with the lightning gun code and with the engine-side implementation of TE_LIGHTNING2. What the lightning gun is actually doing, is shooting 2 beams parallel to the original beam. There is a page on SDA that documents where it goes wrong, but the fail starts when f is normalized but the value isn't put back into f.
TE_LIGHTNING2 ignores the start co-ordinates of the beam, and instead will use the origin of the entity specified as the start point of the beam. Which is why the beams look as if they fly at strange angles. Also, some engines will only display 1 beam per entity. So the correct way to make them all display is to have 2 additional entities for the 2 beams.
But yes, the easiest thing of all is to just remove the extra beams...
_________________
<ekiM> Son, you're writing data structures your CPU can't cache.

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Supa Joined: 26 Oct 2004 Posts: 122 |

Posted: Fri Feb 05, 2010 3:51 pm Post subject: |

http://speeddemosarchive.com/quake/misc/lbug/

Code:
f = p2 - p1; // Supa LG fix begin: kids, this is why you need to stay in school and pay attention in Maths class f = normalize (f); tmp = f_y; f_y = f_x;
f_x = tmp * -1;
f_z = 0;
// Supa LG fix end
f = f * 16;

HTH. HAND.

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c0burn Joined: 05 Nov 2004 Posts: 158 Location: Liverpool, England |

Posted: Fri Feb 05, 2010 4:19 pm Post subject: |

I never really understood what the function was trying to accomplish.

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Wazat Joined: 15 Oct 2004 Posts: 732 Location: Middle 'o the desert, USA |

Posted: Sat Feb 06, 2010 1:23 am Post subject: |

It's probably laden with vestigial code that was meant to go past walls/multiple targets/etc, but was never finished, or was cut back insufficiently at the last minute. Quake is rich with such "features". _________________ When my computer inevitably explodes and kills me, my cat inherits everything I own. He may be the only one capable of continuing my work.

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