Trying to emulate the Inquisitor's grenade attack

[Enjay]

How would this new feature help? (ie what should the code look like?)

[LilWhiteMouse]

What does ZDoom use as it's gravitational constant?

[Gez]

Physics is pretty simple. Vertical velocity increases by one point every tic. First tic is doubled. So after one tic of freefall, your speed is 2, after two tics it's 3, after three tics it's 4, after 987 tics it's 988, etc. See [wiki]falling damage[/wiki].

So, if you apply an initial upward vertical velocity, it'll be decreased by 1 every tic until it's 0, then it jumps to 2 downwards, and 3, 4, 5, etc.

[Edward-san]

What? So easy?

PREPARE FOR THE MATHS ARENA!!!!!

Example:
let's suppose a grenade monster wants to attack a marines base. For now let's say he knows the right calculation. He fires his projectile, with horizontal speed 'm' and vertical speed 'n', with n and m integers (>0). I assume speed is map_unit/tic. Question: how much high can get the projectile (in map units)?
Let's apply what gez said:

So, if you apply an initial upward vertical velocity, it'll be decreased by 1 every tic until it's 0, then it jumps to 2 downwards, and 3, 4, 5, etc.

In this case, at the first tic the number of the map units vertically traversed by the projectile will be 'n', in the second tic it'll be 'n-1', ... in the 'n-1'-th tic it'll be '1' and in the 'n'-th tic it'll be '0.
Hence, the value will be: the summation of the first 'n' values!
Let's use Gauss' equality: such value is 'n*(n+1) / 2'!!
Let's use bit shift: "n*(n+1) >> 1" map units!!!!!!!
So this is the hard truth no one wanted to know!

[edit]And, how much did the projectile traverse horizontally in the meantime? Let's say the horizontal speed will be constant (right?). Hence, each tic the projectile has moved 'm' map units.
Oh, this'll be easy: "n*m" map units!!!!

Hell, if the marine base is placed in the same height as the monster's projectile, the monster can attack it from a distance of?

Ready? "n*m (rising time) + m (there's a tic with speed 0) + n*m (falling time)=2*(n+1)*m" map units!!!!

[edit]No, wrong: when the projectile starts to fall, at the first tic the projectile's speed will be '-2', not '-1', hence:
2*(n+1)*m-m=(2*n+1)*m!!!

[Edward-san]

However, this function has a slight problem: the robot has got two shoulder-mounted weapons where the grenades are supposed to come from but the grenades (one in particular) fire much lower than that - pretty much at foot level, certainly low enough to get caught even on relatively small obstacles.

Btw: isn't it a bug that should be fixed in zdoom code?

[Enjay]

Btw: isn't it a bug that should be fixed in zdoom code?

I was about to a post a "but that's how it is in the original exe" post but I thought I'd better check and... it isn't. I wouldn't say that the projectiles are launching as high as the shoulder canons but they are definitely launching quite a bit higher than they do in ZDoom. It's difficult to tell in all the 320x200 glory of the original and there is no "freeze" command to help me out but I'd estimate that they originate near waist level or possibly even as high as the "mouth".

Bug report filed.

http://forum.zdoom.org/viewtopic.php?f=2&t=32499

[Enjay]

Related to this: A_Warp - I don't understand the first parameter:

ptr_destination: Teleports the calling actor to the pointer they have. See Actor pointers for more information.

I've checked the actor pointers page but I still don't get it. What does "Teleports the calling actor to the pointer they have" mean? All I am trying to do is to raise the height of the Inquisitor shot by having them A_Warp upwards in their first tic. I'm just using 0 as the first argument and it seems to work but even so, I really don't get what that first parameter is supposed to be doing.

Code: Select all

actor TestMe : InquisitorShot replaces InquisitorShot
{
	States
	{
		Spawn:
		UBAM A 0
		UBAM A 0 A_Warp(0, 0, 0, 72, 0, 0, 0) 
		UBAM A 3
		UBAM B 3
		goto spawn+2
	}
}

The 72 is just a test value and may change.

[XutaWoo]

Basically, it sets what actor it warps to. It's limited to the actor's target, tracer, and master and whatever else there is, so that random stuff doesn't happen when you pick a random actor.

[FDARI]

The pointer selector is used to determine what actor you start from. The coordinates and angles given are relative to that actor.

0 = AAPTR_DEFAULT.
Unless otherwise noted, the default actor is SELF.
So warping with reference to AAPTR_DEFAULT is actually a way of teleporting something a given distance from its current position.

AAPTR_TARGET, AAPTR_MASTER and AAPTR_TRACER would reference the corresponding actor.

In addition, you can reference other actors that are identifiable to the game. For example, when a player calls a function that uses actor pointers, AAPTR_PLAYER_GETTARGET will reference whatever actor the player is looking at. AAPTR_PLAYER1 will always reference player one, if that player is in the game, and AAPTR_PLAYER2..8 work in exactly the same way. (Thus you can have an actor warp to a position relative to player 1 at any time, using AAPTR_PLAYER1, regardless of any tids and targets; as long as player1 exists, it will be correctly identified.)

[Enjay]

Thanks for the explanation. It makes more sense now.