[Can't fix] [2.8pre-1190] Projectiles bounce improperly off Actor tops

[Yholl]

I've been working on a weapon that uses the various bounce states to have different impact effects based on what surfaces and actors etc. it hits. This works perfectly, except for one major problem; a bouncing projectile that strikes the top of a monster's hitbox will not go to any bounce state, and will also do no damage. So shooting enemies from above causes your shots to harmlessly ricochet off their heads into the distance.

I've got a test wad put together here that shows off the effect. Give all weapons, go above an enemy with the test chaingun and your shots will bounce off.

Also of note is that the killing shot on a bleeding actor calls Bounce.Actor instead of Bounce.Actor.Creature, not sure if intended or not. Thought I'd mention it.

[Turret49]

I've got this same problem as well, tested with "Doom", "Hexen" and "Grenade" bounce types. When hitting the top or bottom of an actor (be it a monster or a solid decoration), the bouncy projectile will not collide with the actor and instead "slide" over/under them. You can try this out with vanilla ZDoom simply by using the console to summon a spider mastermind, fly over it, then summon a "Grenade" actor onto it. the grenade will just slide over the mastermind's hitbox instead of bouncing or exploding. It's also possible to have the sliding bug occur if a bouncable projectile hits the underside of a monster, like a cacodemon or pain elemental.

This bug happens in both ZDoom and GZdoom.
(tested in [2.9pre-1100-gb2a88c1] & [g2.2pre-1846-gbce9929] respectively, the latest dev builds at time of posting)

[Edward-san]

Does it happen with gzdoom 1.8.6?

[Graf Zahl]

This is most likely something very old. The entire bouncing code is quite a mess, all inherited from Hexen and Strife.

[Turret49]

Does it happen with gzdoom 1.8.6?

I went and downloaded it fresh from the archive, seems so. Also, it's worth mentioning that if the projectile has no x/y velocity, it will just sit there on top of the actor's head.

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This is most likely something very old. The entire bouncing code is quite a mess, all inherited from Hexen and Strife.

There actually was an old bug that was fixed where bounce actors landing on top of others would get stuck, perhaps that's related to this?
viewtopic.php?f=7&t=26804

[Talon1024]

On a related note, projectiles that have the THRUGHOST flag will bounce off the top of GHOST actors when they should go through them. See this issue for specific details.

[Graf Zahl]

So, here's the problem: The missile got the unconditional 'bounce on actors' flag, and the vertical bouncing respects that. The horizontal bouncing does not. And fixing this would break a lot of stuff. Unfortunately the entire thing is such a clusterfuck of messed up ideas that the attempt of fixing it is bound to backfire.

What this needs is some complete deprecation of the entire thing and starting fresh, but that's not something I want to attempt.

[Major Cooke]

Oh shitstains, that's not good.

[Graf Zahl]

What so you expect. If I make it respect that flag properly, crowd A screams because it breaks their mods, if I change the bouncing off the top crowd B will scream. There is no sane way to fix something this comprehensively fucked up.