Programming C, C++, Java, PHP, Ruby, Turing, VB
Computer Science Canada 
Programming C, C++, Java, PHP, Ruby, Turing, VB  

Username:   Password: 
 RegisterRegister   
 bouncing balls
Index -> Programming, Turing -> Turing Help
View previous topic Printable versionDownload TopicSubscribe to this topicPrivate MessagesRefresh page View next topic
Author Message
this_guy




PostPosted: Sun Jul 25, 2004 3:53 pm   Post subject: bouncing balls

i've been trying to get two balls to bounce off each other



i tried using math.distnc to c whether 2 balls r touching, den hav dem change directions but dat didnt look real
Sponsor
Sponsor
Sponsor
sponsor
Paul




PostPosted: Sun Jul 25, 2004 4:21 pm   Post subject: (No subject)

http://www.compsci.ca/v2/viewtopic.php?t=5246
Cervantes




PostPosted: Mon Jul 26, 2004 6:49 am   Post subject: (No subject)

note that my approach to circular collision does not work very well for top down views, though it is excellent for a side view, like slime-volleyball.
for top-down, try thoughtful's approach:

code:

setscreen ("position:centre;centre,graphics:300;300,title:Bouncing Balls,nobuttonbar,offscreenonly")
var totalballs : int := 4
var x, y, dx, dy : array 1 .. totalballs of real
for i : 1 .. totalballs
    x (i) := Rand.Int (50, maxx - 50)
    y (i) := Rand.Int (50, maxy - 50)
    dx (i) := Rand.Int (-3, 3)
    dy (i) := Rand.Int (-3, 3)
end for
var collangle, mass, a1, a2, nX, nY, optimisedP : real

const ballradius := 8
const highestspeed := 5

proc drawscreen
    for i : 1 .. maxx by 20
        Draw.FillStar (i, 0, i + 20, 20, 2)
        Draw.FillStar (i, maxy - 20, i + 20, maxy, 2)
    end for
    for k : 20 .. maxy - 20 by 20
        Draw.FillStar (0, k, 20, k + 20, 2)
        Draw.FillStar (maxx - 20, k, maxx, k + 20, 2)
    end for
end drawscreen

proc ball_movement
    for i : 1 .. totalballs
        %wall bouncing
        if x (i) > maxx - 20 - ballradius then
            dx (i) := -dx (i)
            x (i) := maxx - 20 - ballradius
            x (i) += dx (i)
        end if
        if x (i) < 20 + ballradius then
            dx (i) := -dx (i)
            x (i) := 20 + ballradius
            x (i) += dx (i)
        end if
        if y (i) > maxy - 20 - ballradius then
            dy (i) := -dy (i)
            y (i) := maxy - 20 - ballradius
            y (i) += dy (i)
        end if
        if y (i) < 20 + ballradius then
            dy (i) := -dy (i)
            y (i) := 20 + ballradius
            y (i) += dy (i)
        end if

        x (i) += dx (i)
        y (i) += dy (i)
        if dx (i) > highestspeed then
            dx (i) := highestspeed
        elsif dx (i) < -highestspeed then
            dx (i) := -highestspeed
        end if
        if dy (i) > highestspeed then
            dy (i) := highestspeed
        elsif dy (i) < -highestspeed then
            dy (i) := -highestspeed
        end if
        drawfilloval (round (x (i)), round (y (i)), ballradius, ballradius, blue)
    end for
end ball_movement

proc balls_collide
    for i : 1 .. totalballs
        for k : i .. totalballs
            if k not= i then
                if Math.Distance (x (i), y (i), x (k), y (k)) < ballradius * 2 then
                    %CREDIT :  THOUGHTFUL
                    if y (k) - y (i) not= 0 and x (k) - x (i) not= 0 then
                        collangle := arctand ((y (k) - y (i)) / ((x (k) - x (i))))

                        nX := cosd (collangle)
                        nY := sind (collangle)

                        a1 := dx (i) * nX + dy (i) * nY
                        a2 := dx (k) * nX + dy (k) * nY

                        optimisedP := (a1 - a2)

                        dx (i) -= (optimisedP * nX)
                        dy (i) -= (optimisedP * nY)
                        dx (k) += (optimisedP * nX)
                        dy (k) += (optimisedP * nY)
                        % moves the balls forward 2 steps so they dont get stuck with each other as often
                        x (i) += dx (i)
                        y (i) += dy (i)
                        x (k) += dx (k)
                        y (k) += dy (k)
                    end if
                end if
            end if
        end for
    end for
end balls_collide

loop
    cls
    drawscreen
    ball_movement
    balls_collide
    View.Update
    delay (12)
end loop
DanShadow




PostPosted: Mon Jul 26, 2004 6:35 pm   Post subject: (No subject)

or as done in many programs, create a cute, simple collision detection.
Create a square with slightly smaller parameters than the circle, and make its center the same as the circles. If one of the immediate sides, or edges, or even the middle hits the other circle, write a procedure that checks which general direction (top_right,top_left,bottom_right,bottom_middle,etc. etc.) the opposing circle hits, and change the opposing balls direction to the opposite direction of its original direction, and maybe change its speed a bit. Lol, cheap, but it works.
this_guy




PostPosted: Tue Jul 27, 2004 3:06 pm   Post subject: (No subject)

wow thnx guys...except for danshadow...didnt get wut u said

1 problem, i looked at cervantes, but sometimes 2 balls would get stuck together and rotate around each other.

that happened with smthg i tried 2, but dunno wut da prob is
Cervantes




PostPosted: Fri Jul 30, 2004 6:42 am   Post subject: (No subject)

code:

                        % moves the balls forward 2 steps so they dont get stuck with each other as often
                        x (i) += dx (i)
                        y (i) += dy (i)
                        x (k) += dx (k)
                        y (k) += dy (k)

That is the part that tries to prevent the balls from sticking together. If you find that they are sticking together, do it again.
code:

                        % moves the balls forward 2 steps so they dont get stuck with each other as often
                        x (i) += (2 * dx (i))
                        y (i) += (2 * dy (i))
                        x (k) += (2 * dx (k))
                        y (k) += (2 * dy (k))
DanShadow




PostPosted: Fri Jul 30, 2004 8:55 pm   Post subject: (No subject)

This is an example of what I meant.(the picture attached)
[Open the file for this example]
See the light blue square behind the circle? That is the offset for the radius
in each corner. Now if a part of the second square around the second circle enters inside the first square of the first circle, it initiates a "collision" procedure which repels the second circle (and/or the first) in the opposite direction. If this clears up what I mean, my intention is fufilled.



ballex.bmp
 Description:
Ball Collision Example
 Filesize:  414.06 KB
 Viewed:  4731 Time(s)

ballex.bmp


this_guy




PostPosted: Tue Aug 03, 2004 4:02 pm   Post subject: (No subject)

oh! i c...

kinda cheap, and fake

especially if u hav a lot of diff circles.

but its so much easier:D
Sponsor
Sponsor
Sponsor
sponsor
DanShadow




PostPosted: Tue Aug 03, 2004 6:57 pm   Post subject: (No subject)

hehe, true, true. But a lot of people seem to use that! Its kind of weird, but if so many people do it, why not? Wink
Delta




PostPosted: Thu Aug 05, 2004 11:36 am   Post subject: (No subject)

Because it's inefficient... use cervantes method which is about a hundred times better... I like how you have the engery transfer goin' on there cervantes real smooth use of physics lol... but ya... will balls... don't use a box for collisions... it's common sense...
DanShadow




PostPosted: Thu Aug 05, 2004 3:42 pm   Post subject: (No subject)

Im not saying you SHOULD use box collision detection, im just saying that quite a few people use it, and its easier if you dont understand physics.
Display posts from previous:   
   Index -> Programming, Turing -> Turing Help
View previous topic Tell A FriendPrintable versionDownload TopicSubscribe to this topicPrivate MessagesRefresh page View next topic

Page 1 of 1  [ 11 Posts ]
Jump to:   


Style:  
Search: