in megapov you can have persistent variables through an animation

Chris Calef wrote:
> 
> Hi.  I'm new to this group, but I've been off in my own little cave working on
> the problem of physics-based motion in povray for a little while now.  At the
> moment I'm working on a "frog" that points in a random direction and leaps
> according to a random vector, then slides and when it gets slow enough jumps
> again.  Forgive me if I betray serious ignorance here, but in my
> experimentation I haven't found any way to save persistent variables from one
> frame to the next in povray without writing them out to a text file, so that's
> what I'm doing.  (code snippet below)
> It seems like "querying the host object" is sort of backwards... wouldn't you
> create the projectile object and give it position and move vectors based on
> the known muzzle position and angle?  If you don't know the muzzle position
> and angle because the ship has moved and rotated, then you'd have to apply the
> same transformations to the original muzzle coordinates that you applied to
> the ship... does that make sense? (believe it or not, english actually is my
> first language.)
> 
> #declare gravity_vector = <0,-8,0>;
> #declare drag = 0.9;
> 
> #fopen FrogFile "frog.dat" read
> #read (FrogFile,frog_position,frog_move,rot_y,rot_x)
> #fclose FrogFile
> 
> #declare frog_move = (frog_move + gravity_vector) * drag;
> #declare frog_position = frog_position + frog_move;
> 
> #fopen FrogFile "frog.dat" write
> #write (FrogFile,frog_position,",",frog_move,",",rot_y,",",rot_x,",\n")
> #fclose FrogFile
> 
> If anyone knows how I can save these variables without writing out to frog.dat
> I'd be very happy!
> 
> "Greg M. Johnson" wrote:
> 
> > ryan constantine wrote:
> >
> > > by "query the host object" i mean it can find the end of the muzzle as
> > > well as the direction it is pointing in order to know which drection to
> > > shoot.  maybe the host (space ship) should set global variables
> > > indicating where the muzzle tip is and the direction.  then the laser
> > > would just use the globals.  what do you think?
> >
> > Still confused.
> >
> > EITHER
> > ------------------------------------------------------------
> >
> > // LASER BEAM: SPEED OF LIGHT
> >
> > #declare laserhit=trace(Duck, LaserAim, LaserPosition, Norm);
> >
> > #if( Norm.x!=0&Norm.y!=0&Norm.z!=0)   //syntax may be a bit off
> >          #declare DeadYet=1;
> > #end
> >
> > ---------------------------------------------------
> >
> >  //        OR SHOOT A BUNCH OF BULLETS
> >
> > #declare Bulletposition=Bulletposition+0.1*Bulletveloc;
> > #declare Bulletveloc=Bulletveloc-0.1*y;
> >
> > #if(DeadYet>0.5)
> >     #declare TimeoDeath=TimeoDeath+1;
> > #else
> >     #if(vlength (DuckPostion-Bulletposition)<ContactDistance)  // ala Greg
> >         #declare DeadYet=1;
> >     #end
> > #end

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