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  bouncing a quad back and forth  (Read 1028 times)
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Offline Kommi

Junior Devvie




All opinions will be lined up and shot!


« Posted 2003-06-08 17:15:03 »

OK I have a simple quad drawn on the screen. I use the gl.translatef (x, 0, 0)
and
x = x + .05f
to move it to the right

My question is this. If I wanted to make it change direction after a bit in Java2d I would just say if
(x > Screenwidth)
x = -x;

But in openGL if I try that then the quad goes to its original starting position instead of moving in the -x direction. How can I fix it so when it moves a certain distance to the right it then changes its direction of movement?


Kommi
Offline cfmdobbie

Senior Devvie


Medals: 1


Who, me?


« Reply #1 - Posted 2003-06-08 21:01:50 »

Almost - swap the direction of the increment instead of the x value:

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float dx = 0.05f ;

x = x + dx ;

if(x > Screenwidth)
  dx = -dx ;


The process you mention wouldn't work in Java2D either - you're using x as the absolute position of the quad, not the difference in position.

Hellomynameis Charlie Dobbie.
Offline Kommi

Junior Devvie




All opinions will be lined up and shot!


« Reply #2 - Posted 2003-06-08 21:36:43 »

right thanx

Kommi
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