Computer Science Canada :: View topic

setscreen ("graphics:800;600")
View.Set ("offscreenonly")
var x, y, x2, y2 : int %centre position
var obsx, obsy : int := 300 %obstacle position
var dx, dy, dx2, dy2 : int := -2 %centre and direction/speed
const ballradius : int := 20

randint (x, ballradius, maxx - ballradius) %ball1 random starting x-position
randint (y, ballradius, maxy - ballradius) %ball1 random starting y-position

randint (x2, ballradius, maxx - ballradius) %ball2 random starting x-position
randint (y2, ballradius, maxy - ballradius) %ball2 random starting y-position

proc obs %obstacles
drawfillbox (obsx - 50, obsy - 50, obsx + 50, obsy + 50, yellow)
end obs

proc ball1
drawfilloval (x, y, ballradius, ballradius, red)
x += dx
y += dy
if x >= maxx - ballradius or x <= ballradius or Math.DistancePointLine (x, y, obsx - 50, obsy + 50, obsx - 50, obsy - 50) <= ballradius or Math.DistancePointLine (x, y, obsx + 50, obsy + 50, obsx
+ 50, obsy - 50) <= ballradius then
dx := -dx
elsif y >= maxy - ballradius or y <= ballradius or Math.DistancePointLine (x, y, obsx - 50, obsy + 50, obsx + 50, obsy + 50) <= ballradius or Math.DistancePointLine (x, y, obsx - 50, obsy - 50,
obsx + 50, obsy - 50) <= ballradius then
dy := -dy
elsif Math.Distance (x, y, obsx - 50, obsy + 50) = ballradius or Math.Distance (x, y, obsx - 50, obsy - 50) = ballradius or Math.Distance (x, y, obsx + 50, obsy + 50) = ballradius or
Math.Distance (x, y, obsx + 50, obsy - 50) = ballradius then
dx := -dx
dy := -dy
end if
end ball1

proc ball2
drawfilloval (x2, y2, ballradius, ballradius, white)
x2 += dx2
y2 += dy2
if x2 >= maxx - ballradius or x2 <= ballradius or Math.DistancePointLine (x2, y2, obsx - 50, obsy + 50, obsx - 50, obsy - 50) <= ballradius or Math.DistancePointLine (x2, y2, obsx + 50, obsy +
50, obsx + 50, obsy - 50) <= ballradius then
dx2 := -dx2
elsif y2 >= maxy - ballradius or y2 <= ballradius or Math.DistancePointLine (x2, y2, obsx - 50, obsy + 50, obsx + 50, obsy + 50) <= ballradius or Math.DistancePointLine (x2, y2, obsx - 50, obsy -
50, obsx + 50, obsy - 50) <= ballradius then
dy2 := -dy2
elsif Math.Distance (x2, y2, obsx - 50, obsy + 50) = ballradius or Math.Distance (x2, y2, obsx - 50, obsy - 50) = ballradius or Math.Distance (x2, y2, obsx + 50, obsy + 50) = ballradius or
Math.Distance (x2, y2, obsx + 50, obsy - 50) = ballradius then
dx2 := -dx2
dy2 := -dy2
end if
end ball2

loop
drawfillbox (0, 0, maxx, maxy, black)
obs
ball1
ball2
View.Update
delay (5)
end loop

Author:	Paul [ Fri Apr 09, 2004 4:08 pm ]
Post subject:
the reason for that is the ball isn't bouncing off the edge of the square properly, I had the same problem in paddleball. I didn't take a close look at the code but there could be some possiblilities: 1. the code only checks for the most up, left, down right, coordinates of the ball, so when the ball comes towards the square's corner diagonally, it doesn't detect the collision at all. 2. the collision checks for coordinates that are bypassed because of the large increments of the coordinates of the ball. IE: the wall is at 230, the ball checks for 229, doesn't detect anything, the ball moves 5 forward, checks for 234, and misses the wall. I dunno how to fix it, because I haven't learned that complex equation that zylum was going to explain.

Author:	gamer [ Fri Apr 09, 2004 4:35 pm ]
Post subject:
thnx paul, after i looked at ur 2nd suggestion i tried changing the speed of the ball to 1 instead of 2.... and everythin was fine!! however, remember i had the other problem of wanting one ball to move at random speed (ie: speed of 1 for 2 seconds then speed of 3 for 2 seconds etc)....so would it stil work?? n how?

Author:	gamer [ Fri Apr 09, 2004 4:48 pm ]
Post subject:
no no no....like 4get the collision for a sec....what i need is one ball travel at a varying pace/speed so if normally it goes at speed of 1, then one or two sec later it goes faster OR slower......n continues but if talking about collision of the obstacle's corner, i think i must need the speed to be 1.....then maybe i can random the delay? lol but then delay applies for both of the balls, n i need just one ball to be delay, how can i do this??

Author:	Paul [ Fri Apr 09, 2004 4:54 pm ]
Post subject:
so one ball travels at a constant speed, the other speed varies. Maybe have a counter inside the loop, and have the 2 balls increase by 2 different variables, when the counter counts that the loop has run say, 10 times, it changes the increase variable from 1 to 3, then after it runs another 10 times, it changes to 2, so just randint inside the loop? I dunno about the delay thing though. It could probably mess up your collision detection too.

Author:	gamer [ Fri Apr 09, 2004 5:27 pm ]
Post subject:
damn even tho i change the speed to 1 the corner detection would screwup if i let the program run longer.....i guess this isnt the way to fix it wut should i do then?