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Re: [pygame] trajectory
Not built into pygame, but there is a good one on the pygame wiki:
http://pygame.org/wiki/2DVectorClass
On Wed, Jul 20, 2011 at 04:33:16PM +0200, Nathan BIAGINI wrote:
> There is a pygame object to create a 2d vector?
>
> 2011/7/20 Joe Ranalli <jranalli@xxxxxxxxx>
>
> Yes a vector is probably appropriate.
>
> On Wed, Jul 20, 2011 at 10:20 AM, Nathan BIAGINI <nathan.open@xxxxxxxxx>
> wrote:
>
> Ok. But all the calcul of how long the bullet will take to reach the
> target etc... will be made byn using vector? I mean, using a vector
> still viable?
>
> 2011/7/20 Joe Ranalli <jranalli@xxxxxxxxx>
>
> It depends what you're trying to do.
>
> If you draw the straight line between the tower and the enemy and
> use that vector to translate a bullet each tick, the bullets might
> miss the enemy. Think about it this way, the bullet moves 2 steps
> toward the enemy, then the enemy moves 1 step, then the bullet moves
> 2, etc. Because the enemy moves the bullet will have to change its
> direction through the flight. So you could calculate the direction
> vector between the bullet and the enemy every tick and have the
> bullet move that direction. That would make the bullets kind of arc
> to the target.
>
> If you want to have the bullet go straight to the right spot, you
> need to:
> 1) calculate how long the bullet will take to get to the enemy
> 2) calculate where the enemy will be at that time (newposition)
> 3) calculate how long it will take the bullet to get to newposition
> 4) recalculate newposition based on the new time
>
> Technically you could iterate that repeatedly until newposition
> converges. Practically, iterating once probably gets you close
> enough unless the movement is extremely complicated.
>
> On Wed, Jul 20, 2011 at 9:14 AM, Nathan BIAGINI
> <nathan.open@xxxxxxxxx> wrote:
>
> Hi everyone,
>
> i would like to know what are the common way to handle
> "trajectory" in a 2d game. In fact, i think of writing a tower
> defense game and i wonder how to handle the trajectory of the
> missile launch by the towers. I though of getting the pos of the
> tower and the target and create a vector between this two
> entitites to make a sprite translation of this vector but there is
> maybe some tricky stuff to do it.
>
> Thanks in advance and happy game making all :-)