[crossfire] Smooth movement

[Lalo Martins]

Ok, I searched for the original thread to ressurect it, but couldn't
find it, so here goes a new one.

A few weeks ago, when Mark started talking about his new movement code,
there was some talk about "smoothing" movement - drawing the image in
partial locations between tiles, so that movement doesn't look so jerky.

The problem is that everything happens in a tick-based timeframe, so
until you move, there's no way to be sure where you will be next turn;
and starting "smooth" movement only after you already moved would be
worse, because for some time, you would seem to be in one tile while
you're actually already on the next one (if "you" are a monster, this
would cause players to shoot at the wrong tile).

End summary.

Now, the solution to this came to me two days ago just before sleep.
I'm surprised nobody came up with it before.  Although it has *serious*
implications - it changes drastically the way the game works - but then
it means it's the best time to introduce it now, together with Mark's
other changes.  And I think it's a tangible improvement.

Basically, it consists on accepting "input" (whether it's actual input
from the user, or a decision from the monster AI code) at a point in
time half a tick before when the object actually gets its tick.  Think
of that as neural impulse delay.

So, assuming the character was still then moves south, and its speeed is
such that it gets one tick at each T (T being global ticks):

Time | input      | face position                      | actual position
-------------------------------------------------------------------------
T    |   -        | X,Y                                | X,Y
T+5  | move south | X,Y                                | X,Y
T+6  |   -        | X,Y+0.1                            | X,Y
T+7  |   -        | X,Y+0.2                            | X,Y
T+8  |   -        | X,Y+0.3                            | X,Y
T+9  |   -        | X,Y+0.4                            | X,Y
T+10 |   -        | X,Y+0.5                            | X,Y+1
   (TICK)         |   (exactly on the line b/w tiles)  |
T+11 |   -        | X,Y+0.6                            | X,Y+1
T+12 |   -        | X,Y+0.7                            | X,Y+1
T+13 |   -        | X,Y+0.8                            | X,Y+1
T+14 |   -        | X,Y+0.9                            | X,Y+1
T+15 | move south | X,Y+1                              | X,Y+1
T+16 |   -        | X,Y+1.1                            | X,Y+1
...

In a future version, this logic could also be useful for weapon-swing
animations, attack sounds, etc etc.

Does that make sense?

best,
                                               Lalo Martins
--
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       then they seem improbable, and then, when we
       summon the will, they soon become inevitable.
--
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