[Won't fix] Dehacked Projectile Speed

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Dehacked Projectile Speed

Postby EarthQuake » Thu Dec 25, 2003 10:50 am

Last edited by EarthQuake on Wed Dec 31, 2003 1:41 pm, edited 1 time in total.
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Postby Ultraviolet » Thu Dec 25, 2003 11:19 am

You seem to be missing the fact that fast projectiles WERE fixed. It wasn't a bug in previous versions of ZDoom, it was a bug dating back to the original. You couldn't make a projectile go past something like a speed of 35 or it would always shoot off to some weird angle. A recent version of ZDoom DID fix that by upping it apparently a LOT. If the projectile hits seemingly near-instantaneously when you fire it, you've got real bullet-speed anyway, so I'd say it's safe to just be happy with it. :P (It's going above 200 that's your problem, isn't it?)

Anyway, the way I heard (or assumed) it was it's some issue of floating-point precision for a given variable used in the game blah blah blah and in order to fix that you'd have to use even more precision and it would take up more memory. For only one variable that would be no big deal, but if there are several variables that have to have their precision increased then it's going to take up a lot of memory. Is having projectiles faster than 200 worth a potential big increase in memory/processor usage?
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Postby Ultraviolet » Thu Dec 25, 2003 11:26 am

I seem to be only able to reproduce your problem if I turn up my projectile speed to some ridiculous number (last I tried was 3000), and then only if I'm looking down about 15 degrees. However, it doesn't seem that the projectile moves any faster than it did when I had it set to 120. It seems there is a speed cap, whether intentional or not. Perhaps that cap is based on my machine's ability to move a projectile any faster? We'll see when I get my new machine. (Right now I'm running a 300 megahertz processor, see... and 256 megs of PC133 but only on a 100 megahertz system bus.)
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Postby Graf Zahl » Thu Dec 25, 2003 1:21 pm

This looks to be a different problem. I wouldn't go so far to call this a bug. It's probably just an inaccuracy that's unavoidable with such high numbers. I did a quick debugger check but I couldn't find any overflow in the calculations.
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Postby EarthQuake » Thu Dec 25, 2003 3:21 pm

Last edited by EarthQuake on Wed Dec 31, 2003 1:41 pm, edited 1 time in total.
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Postby HotWax » Fri Dec 26, 2003 3:18 am

This may simply be an unavoidable side-effect to doing something Doom was never intended to do -- make a projectile move so insanely fast that it seems to be a hitscan weapon.
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Postby Graf Zahl » Fri Dec 26, 2003 7:15 am

Ok, here's the reason for this behavior:

Doom (and ZDoom) perform horizontal and vertical movement independently of each other. So the projectile moves forward the full amout of the current move and after that is done the vertical movement is done. The problem is that the projectile would end up far below the floor so its height is adjusted (to exactly the floor height) and it explodes. Of course this position is not where the true intersection between the projectile's trajectory and the floor is. To fix this the movement code would have to be completely rewritten to either perform both horizontal and vertical movement at the same time or to do vertical movement for each of the steps the horizontal movement is already split into. Believe me, this is a major rewrite of the entire movement code that is probably not worth the effort (unless Randy has an idea how to do it in a simpler way.)
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Postby Lexus Alyus » Mon Dec 29, 2003 4:44 am

I think your being picky. I've said so many times that I used a projectile speed of 255 and it looked just fine. Fair enough, I've mixed it in with an hitscan attack too, but it gets the effect and looks okay. Why should it have to be instant anyway? Are real bullets instant? A gun fires something (well, a bullet of course) and that something is physical and has to actually move through the air. So, 200 or 255 is more than enough and I personally can't see why you would want it to be any faster...

Also, what Graf Zahl said about the horizontal and vertical thing :-D.

So, set it to 255 and be done with it! :-D

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Postby randi » Fri Jan 02, 2004 9:12 pm

I'm glad somebody looked at this while I was on vacation so I don't have to. This is something I thought about when I was changing the X/Y movement to allow for more than two subdivisions.

Rewriting the physics code is at the top of my "would be nice, but I cringe at the thought of actually doing it" list. It's so complicated, I think it would be very difficult for me to do a nice rewrite that still feels like Doom.
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