A_SeekerMissile vertical issue

[Minigunner]

A_SeekerMissile tends to ignore pitch and, as a result, the more vertical the pitch, the faster the projectile goes.

Here's a way to reproduce this bug:
-Create a monster that fires a slightly-homing missile (A_SeekerMissile(1,1))
-Run ZDoom on a tall map
-Summon the monster
-Fly high above it, and when it attacks, observe the missile's movement.

[Major Cooke]

Let's not forget, going under has the same issue.

[randi]

Fixed.

[Graf Zahl]

Let's be clear about this:

This is precisely the kind of change ZDoom has gotten a bad reputation for. Having this as an optional seeking mode is fine but changing every single seeker missile that had been created is sure not.

This is not so much about the speed change but about the fact that the function now behaves completely differently than before and certain evasion techniques that previously worked no longer will. The old function did not change vertical velocity when the missile was in the height range of the target but the new one does. This is a major behavioral change that is sure to cause problems.

All around: Not a good idea unless made 'opt-in'.

[Edward-san]

What about if you define P_SeekerMissileEx and A_SeekerMissileEx (or some other name) as the improvements of P_SeekerMissile and A_SeekerMissile? *fading away*

[Gez]

What about if you define P_SeekerMissileEx and A_SeekerMissileEx (or some other name) as the improvements of P_SeekerMissile and A_SeekerMissile? *fading away*

A_BlahBlahEx is a {{deprecated}} way of doing things now that default values can be given for parameters. It made sense when adding a parameter required changing all existing calls to the function, but now you can just keep on piling optional parameters without breaking anything, so it's better to have a single function with a lot of params rather than twenty-thousand different functions that all do the same thing except with a different option.

And, guess what? [wiki]A_SeekerMissile[/wiki] has a "flag" field that has still plenty of slots available!

[Enjay]

This is not so much about the speed change but about the fact that the function now behaves completely differently than before and certain evasion techniques that previously worked no longer will. The old function did not change vertical velocity when the missile was in the height range of the target but the new one does. This is a major behavioral change that is sure to cause problems.

I haven't had a chance to check this but I will confirm that avoiding seeking missiles by exploiting the fact they have limited ability to seek vertically is a significant part of my gameplay.

[InsanityBringer]

if at the very least running in circles with a seeker missile after you doesn't cause them to crash into the ground, that'd be fine. I've seen several cases where seeker missiles slowly drop over time.

[Graf Zahl]

Yes, that's the evasion technique I was referring to and which Enjay explained. It's an integral part of how the Heretic's Mummy's projectile works and changing this is a serious gameplay alteration and these should be avoided at all costs.

Now, of the original games this only concerns Heretic and Hexen so the outcry will be less than if this was something done by Doom originally. But if this was Doom rest assured that the community's reaction will be less than favorable and yet more food for the 'ZDoom is no longer Doom' crowd.

I sure do not approve of this change as it seriously bumps up the difficulty of monsters using such projectiles.

And, guess what? [wiki]A_SeekerMissile[/wiki] has a "flag" field that has still plenty of slots available!

And now take a guess how I will address this 'problem'.

[Gez]

It's actually also a critical part of evading revenant tracers when they are above. Then they can be dodged mostly like normal projectiles, without having to worry too much about them looping around and hitting you in the back since they'll continue their downward trajectory and crash on the ground.

[Graf Zahl]

The Revenant tracer uses different code (which also suffers from the vertical velocity issue, btw.) so it's not affected by this (non-)fix.

[Major Cooke]

So is it now going to be made into a flag option? I'm about to test drive it to see how it all works out in a moment, but it'd be nice in case if something is breaking...

[Graf Zahl]

If I find some time to check the code, yes. But that won't be until the weekend.

[Graf Zahl]

I did some tests and all my suspicions were true: All the common evasion techniques I normally use againsz Heretic's Mummy are broken. This change needs to be reverted for existing definitions and made an option.

[Major Cooke]

Cool. Can't wait to see this in GZdoom too.