Moving game pieces using atan2().
I check to see if the position (px,py)
has reached the target (tx,ty) by
absolute values of positions minus targets.
If they havent reached the destination I increment
by the dx I got from the atan2() calculation.
This works as it is. But I cannot actually control the speed.
If I want it to go faster, say speed 8, there are certain
situations where condition if abs(px-tx)<3 and abs(py-ty)<3 will never
be met and piece will just go forever. And I cant fine tune the <3 either
because sometimes the math just wont allow it.
How do I write code or think about this to move my sprite so I can actually control
the speed and/or accuracy?
Must be able to move any direction at any angle.
Thank you.
speed=5 px,py=getxy(location) tx,ty=getxy(destination) local angle=atan2(ty-py,tx-px) dx=sin(angle)*speed dy=cos(angle)*speed --PROBLEM HERE function _update_move() if abs(px-tx)<3 and abs(py-ty)<3 then --AND PROBLEM HERE --ARRIVED AT LOCATION else px+=dx py+=dy end end |
compute how many frames it will take to reach the destination
(distance/speed)
and stop when frames left to travel is <=1
beware of overflows when computing the distance, and of divisions by 0 if you start at destination
thanks for the response @RealShadowCaster. will take me a little while to figure out how to implement.
function _update_move() local lx,ly=tx-px,ty-py if lx==0 and ly==0 then --and problem here --arrived at location ?"arrived!",52,2,11 else px+=mid(dx,lx,0) py+=mid(dy,ly,0) end end |
By taking the intermediate value of mid() between the "difference from current location to destination", the "current speed", and the "distance (final speed) 0", dx and dy will be either "0", "the set speed", or "the extra distance in the final frame".
This ensures that the remaining distance and dx dy are always subtracted by the same value in the last frame.
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