Odd interface, but alot of power under the hood.
Thanks,
David JJ
in my humble opinion | [EMAIL PROTECTED]
On Nov 15, 2004, at 12:00 PM, [EMAIL PROTECTED] wrote:
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Message: 7
I'm looking to finish a small game my son suggested but I'm stumped on code that will produce the effects I need. The two player game basically involves trying to knock the opponents "marble" out of the (square) playing area. This means I need to script each marble (WASD or arrow keys) to have a radius, mass and velocity. The collisions between marbles must be like billiard balls on a nearly frictionless surface. Mass means that the marbles can transfer energy and increase/decrease speed not only with a direction key held down, but also through the collisions.
Has anyone written any scripts like this?
I can code this in Basic as follows, but need to know the best way to do it in Revolution Dreamcard.
Here's how it might look in Basic (but with only one ball the player can control) ...
int numOfBalls=2 // Change to add marbles. Just be sure to specify the starting position, mass, and radius for each marble. int elasticity=0.5 // Elasticity is a value from 0 to 1: 0 will result in perfectly INELASTIC collisions (masses stick together), and a value of 1 will result in perfectly ELASTIC collisions
float X[numOfBalls],Y[numOfBalls] float Vx[numOfBalls],Vy[numOfBalls] float M[numOfBalls] float radius[numOfBalls]
// INITIAL VALUES SECTION -- Make sure to add more for each ball you add
radius[0]=28 // Marble size M[0]=25 // Marble mass X[0]=100 // X coordinate Y[0]=370 // Y coordinate
radius[1]=28 M[1]=25 X[1]=660 Y[1]=370
// GAME LOOP SECTION
int control repeat int key=raw key scancode(keyboard raw key) // Controls if up then Vy[control]=Vy[control]-0.5 'all values started at 0.5 if down then Vy[control]=Vy[control]+0.5 if left then Vx[control]=Vx[control]-0.5 if right then Vx[control]=Vx[control]+0.5 if pressed(6) // z key slows down the velocities each frame int stopCount for stopCount=0 to numOfBalls-1 Vx[stopCount]=Vx[stopCount]/1.1 Vy[stopCount]=Vy[stopCount]/1.1 next stopCount end if int a,b for a=0 to numOfBalls-1 for b=0 to numOfBalls-1 if b>a // only check combinations that haven't been checked yet; for example, there's no need to check (0,1) and then (1,0). float xDiff=X[b]-X[a] float yDiff=-(Y[b]-Y[a]) float distance=sqrt(xDiff^2+yDiff^2) if distance<radius[a]+radius[b] 'if marbles a and b are touching
// find angle between marbles if xdiff>=0 then float diffdir= invtan(ydiff/xdiff) if xdiff<0 then float diffdir= invtan(ydiff/xdiff)+180 float dVx=Vx[a]-Vx[b] float dVy=-(Vy[a]-Vy[b]) float totVel=sqrt(dVx^2+dVy^2) if totVel>0 if dVx>=0 then float veldir =invtan(dVy/dVx) if dVx<0 then float veldir = invtan(dVy/dVx)+180 // the impulse is the amount of transferred momentum. The impulse can only be transferred along the point of contact. float impulse=(1+elasticity)*(M[a]*M[b])/(M[a]+M[b])*totVel*cos(veldir- diffdir) float VxfA=-impulse*cos(diffdir)/M[a]+Vx[a] float VyfA=impulse*sin(diffdir)/M[a]+Vy[a] float VxfB=impulse*cos(diffdir)/M[b]+Vx[b] float VyfB=-impulse*sin(diffdir)/M[b]+Vy[b]
Vx[a]=VxfA
Vy[a]=VyfA
Vx[b]=VxfB
Vy[b]=VyfB
end if
float dX=(radius[a]+radius[b]-distance)/2*cos(diffdir)
float dY=-((radius[a]+radius[b]-distance)/2*sin(diffdir))
X[a]=X[a]-dX
Y[a]=Y[a]-dY
X[b]=X[b]+dX
Y[b]=Y[b]+dY
end if
end if
next b
next a
float totalEnergy=0,totalMomentumX=0,totalMomentumY=0
for a=0 to numOfBalls-1
totalEnergy=totalEnergy+M[a]*(Vx[a]^2+Vy[a]^2)/2 //calculate the
kinetic energy per ball, (1/2)*mass*velocity
totalMomentumX=totalMomentumX+M[a]*Vx[a] //momentum is mass*velocity
totalMomentumY=totalMomentumY+M[a]*Vy[a] //x momentum and y
momentum can be calculated separately
X[a]=X[a]+Vx[a]
Y[a]=Y[a]+Vy[a]
if X[a]>740 //768 field width - ball width
X[a]=740
Vx[a]=-abs(Vx[a])
else if X[a]<28
X[a]=28
Vx[a]=abs(Vx[a])
end if
if Y[a]>740 //768 field width - ball width
Y[a]=740
Vy[a]=-abs(Vy[a])
else if Y[a]<28
Y[a]=28
Vy[a]=abs(Vy[a])
end if
if a=control
set pen color blue //player controlled ball blue
else
set pen color yellow //other balls yellow
end if
fill oval X[a]-radius[a],Y[a]-radius[a] to
X[a]+radius[a],Y[a]+radius[a]
next a
draw frame
// Clear the screen for the next frame
int erase
for erase=0 to numOfBalls-1
set pen color white
fill oval X[erase]-radius[erase],Y[erase]-radius[erase] to
X[erase]+radius[erase],Y[erase]+radius[erase]
next erase
until pressed(12)
All help appreciated,
David JJ
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