Object oriented

I think the method I have to determine if the ball should bounce is - not very good. It is like this:

for yspeed inverting

if ball.x+ball.width > object.x
and ball.x < object.x+object.width
and ball.y+ball.height >= object.y
and ball.y <= object.y+object.height

for xspeed inverting

if ball.y+ball.height > object.y
and ball.y < object.y+object.height
and ball.x+ball.height >= object.x
and ball.x <= object.x+object.width

What do you guys think?



/J Lindroos

Come on guys, this is a simple new-beginner question. Everyone who have ever made a platform game should have confronted this!


/J Lindroos

[edited by - JL on December 13, 2002 2:41:37 AM]

im doing a test for each of the four sides of a block, just to be sure it wont move through it *g*.

here Size is the radius of the Ball, MinX, MaxX, MinY, MaxY are the limits of the box/object. XVel, YVel are the velocity of the ball in x,y direction.

if ((YPos>=MaxY+Size)&&(newY<=MaxY+Size)) {
float ISX=XPos+(XVel*(MaxY-YPos)/YVel);
if ((ISX>=MinX-Size)&&(ISX<=MaxX+Size)) {
newX=ISX; newY=MaxY+Size;
YVel=-YVel;
return 1;
}
}
else if ((YPos<=MinY-Size)&&(newY>=MinY-Size)) {
float ISX=XPos+(XVel*(MinY-YPos)/YVel);
if ((ISX>=MinX-Size)&&(ISX<=MaxX+Size)) {
newX=ISX; newY=MinY-Size;
YVel=-YVel;
return 1;
}
}
else if ((XPos<=MinX-Size)&&(newX>=MinX-Size)) {
float ISY=YPos+(YVel*(MinX-XPos)/XVel);
if ((ISY>=MinY-Size)&&(ISY<=MaxY+Size)) {
newX=MinX-Size; newY=ISY;
XVel=-XVel;
return 1;
}
}
else if ((XPos>=MaxX+Size)&&(newX<=MaxX+Size)) {
float ISY=YPos+(YVel*(MaxX-XPos)/XVel);
if ((ISY>=MinY-Size)&&(ISY<=MaxY+Size)) {
newX=MaxX+Size; newY=ISY;
XVel=-XVel;
return 1;
}
}

Finally! Thank you very much.

Just one thing. The ball in my case is not round, it is a rectangular image, but I suppose it is better to make it round, i.e just use the radius of the ball. Another question is, why does this function always return 1?

This seems to be what I have been looking for, thankyou again!



/J Lindroos

it doesnt.. its hard to see without proper formation, but return 1 is only inside the if (ISX bla) parts. of course at the very end of this should be a return 0.

a ball is easier to test and if your blocks are axis aligned you will only see a difference if the ball hits a corner.

maybe the math isnt 100% correct. im still not sure what exactly i did there.. maybe i SHOULD start commenting my code, so i will know what i was thinking when i wrote it.. but it worked well in my pong and breakout clones *g*

if you want the whole code:
http://festini.device-zero.de/downloads/pongsrc.zip
or http://festini.device-zero.de/downloads/index.shtml