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# Collision
# 3 "balls" reflect on the walls and can collide
# see http://www.geocities.com/vobarian
print "The return key ends the program."
clg
fastgraphics
# graphics window size
gwidth = 300
gheight = 300
graphsize gwidth,gheight
# feel free to change the radius of the balls and their masses
# radius
r1 = 15
r2 = 15
r3 = 15
# masses
m1 = r1*r1*r1
m2 = r2*r2*r2
m3 = r3*r3*r3
# initial positions and velocities
x1 = rand * (gwidth - 2*r1) + r1 : y1 = r1
vx1 = 10*rand - 5 : vy1 = 3*rand
x2 = rand * (gwidth - 2*r2) + r2 : y2 = gheight - r2
vx2 = 10*rand - 5 : vy2 = -3*rand
x3 = rand * (gwidth - 2*r3) + r3 : y3 = gheight - r3*2
vx3 = 10*rand - 5 : vy3 = 6*rand
kollision = 0 # do we have a collision (1 yes, 0 no)
loopz:
c = key()
if c = 16777220 then goto ende
clg
gosub zeichne
refresh
#pause .01
gosub iskollision
if kollision = 0 then goto m1
gosub getkollision
gosub getnewpos
m1:
gosub wandball1
gosub wandball2
gosub wandball3
m2:
gosub getnewpos
goto loopz
getnewpos:
x1 = x1 + vx1
y1 = y1 + vy1
x2 = x2 + vx2
y2 = y2 + vy2
x3 = x3 + vx3
y3 = y3 + vy3
return
iskollision:
kollision = 0
if sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)) < r1 + r2 then kollision = 1 : sound 400,2
if sqrt((x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3)) < r1 + r3 then kollision = 2 : sound 400,2
if sqrt ((x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3)) < r2 + r3 then kollision = 3 : sound 400,2
return
wandball1:
if ( x1 > gwidth - r1 and vx1 > 0 ) or ( x1 < r1 and vx1 < 0 ) then vx1 = -vx1
if ( y1 > gheight - r1 and vy1 > 0 ) or ( y1 < r1 and vy1 < 0 ) then vy1 = -vy1
return
wandball2:
if ( x2 > gwidth - r2 and vx2 > 0 ) or ( x2 < r2 and vx2 < 0 ) then vx2 = -vx2
if ( y2 > gheight - r2 and vy2 > 0 ) or ( y2 < r2 and vy2 < 0 ) then vy2 = -vy2
return
wandball3:
if ( x3 > gwidth - r3 and vx3 > 0 ) or ( x3 < r3 and vx3 < 0 ) then vx3 = -vx3
if ( y3 > gheight - r3 and vy3 > 0 ) or ( y3 < r3 and vy3 < 0 ) then vy3 = -vy3
return
getkollision:
#normal vector un = unx, uny
if kollision = 1 then
s = sqr((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2))
unx = (x2 - x1) / s
uny = (y2 -y1) / s
endif
if kollision = 2 then
s = sqr((x1-x3)*(x1-x3) + (y1-y3)*(y1-y3))
unx = (x3 - x1) / s
uny = (y3 -y1) / s
endif
if kollision = 3 then
s = sqr((x2-x3)*(x2-x3) + (y2-y3)*(y2-y3))
unx = (x3 - x2) / s
uny = (y3 -y2) / s
endif
#tangential vector ut
utx = -uny : uty = unx
if kollision = 1 then
#tangential velocities vt1, vt2 (skalar)
vt1 = utx*vx1 + uty*vy1
vt2 = utx*vx2 + uty*vy2
#normal velocities vn1, vn2 (skalar)
vn1 = unx*vx1 + uny*vy1
vn2 = unx*vx2 + uny*vy2
endif
if kollision = 2 then
#tangential velocities vt1, vt2 (skalar)
vt1 = utx*vx1 + uty*vy1
vt2 = utx*vx3 + uty*vy3
#normal velocities vn1, vn2 (skalar)
vn1 = unx*vx1 + uny*vy1
vn2 = unx*vx3 + uny*vy3
endif
if kollision = 3 then
#tangential velocities vt1, vt2 (skalar)
vt1 = utx*vx2 + uty*vy2
vt2 = utx*vx3 + uty*vy3
#normal velocities vn1, vn2 (skalar)
vn1 = unx*vx2 + uny*vy2
vn2 = unx*vx3 + uny*vy3
endif
# 1-dimensional collision formulas for the normal
# velocities after collision vn1n, vn2n
# the tangential component of the velcities does not change
vn1n =( (m1-m2)*vn1 + 2*m2*vn2 ) / (m1+m2)
vn2n =( (m2-m1)*vn2 + 2*m1*vn1 ) / (m1+m2)
# vectors after collision: tangential (vt1n,vt2n) and normal (vt1n,vt2n)
vn1nx = unx * vn1n : vn1ny = uny * vn1n
vn2nx = unx * vn2n : vn2ny = uny * vn2n
vt1nx = utx * vt1 : vt1ny = uty * vt1
vt2nx = utx * vt2 : vt2ny = uty * vt2
# tangential and normal vector add to resulting velocities
if kollision = 1 then
vx1 = vt1nx + vn1nx : vy1 = vt1ny + vn1ny
vx2 = vt2nx + vn2nx : vy2 = vt2ny + vn2ny
endif
if kollision = 2 then
vx1 = vt1nx + vn1nx : vy1 = vt1ny + vn1ny
vx3 = vt2nx + vn2nx : vy3 = vt2ny + vn2ny
endif
if kollision = 3 then
vx2 = vt1nx + vn1nx : vy2 = vt1ny + vn1ny
vx3 = vt2nx + vn2nx : vy3 = vt2ny + vn2ny
endif
return
zeichne:
color black
rect 0,0,gwidth,gheight
color clear
rect 1,1,gwidth-2,gheight-2
color red
circle x1,y1,r1
color blue
circle x2,y2,r2
color green
circle x3,y3,r3
return
ende:
print "Bye!"
end
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