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 Calculate stopping distance  (Read 1732 times) 0 Members and 1 Guest are viewing this topic.
Dreamcatchermatt

Junior Devvie

 « Posted 2010-05-13 16:33:45 »

As part of my waypoint following algorythem, I want my character to accellerate towards a waypoint untill it reaches a point (that should be half way) where it must start accellerateing in the opposite direction to stop in-time, landing on the waypoint.

My character has three Vector2D(double x, double y) vectors; position, velocity and acceleration.

currently my waypoint following logic is;
 1  2  3  4  5  6  7  8  9  10  11  12  13 // if there are waypoints left to go toif(waypoints.Size() > 0){    boolean x = NavigateToWaypoint(waypoints.Peek());    if(x)    {        waypoints.Pop();    }     else    {        STOP();    }}

the STOP() method just sets the 'i am navigateing now' flag to false, stopping the Update() method for my navigation class from running.

 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18 NavigateToWaypoint(Vector2D waypoint){    if( // stopping distance > distance to waypoint)    {         // break by accellerateing in opposite direction to waypoint.         return false;    }    else if( // stopping distance < distance to waypoint )    {         // accellerate towards waypoint ('ahead full impulse!')        return false;    }    else if(distance to waypoint < 100)    {        // stop the ship, we're there        return true;    } }

what i'm asking here is how to calculate the stopping distance X for velocity V at acceleration A.

I know its somthing similar to v(end) = v(start) * 2/AX but i'm also sure that this is not it

I used to know all these formuli back at school - now I cant for the life of me remember what it is, and serching around on google has got me lots of equations that are either way too complicated (wikipedia ) or not anything I recognise.

if theres any math guys out there who can gove me some hints that would be great.
Eli Delventhal

JGO Kernel

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Game Engineer

 « Reply #1 - Posted 2010-05-13 17:21:14 »

Have a look here:

http://www.java-gaming.org/topics/calculating-acceleration-and-decelleration-to-reach-a-certain-point-in-time/20093/view.html

I asked pretty much the same question towards the end of the thread.

See my work:
OTC Software
Dreamcatchermatt

Junior Devvie

 « Reply #2 - Posted 2010-05-13 20:18:35 »

Ahhhhhhhh, yeh, that's the one i had half-remembered:

Yeah, that's the discrete (sampled) version of the formula pjt33 posted earlier: s = ut + (1/2)*at^2

The summation s(n-1) can be simplified to n(n-1)/2, and then the relation between the two equations becomes more obvious.

chears for that

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