function [posx, posy]=computetraj(drawcodes,ink);

[numcases, numcode]= size(drawcodes);
maxtime = size(drawcodes,2)/4;
dcodes = .001*drawcodes.*ones(numcases,numcode)*20;    

stiffu = dcodes(:,1:maxtime);
stiffd = dcodes(:,1+maxtime:2*maxtime);
stiffl = dcodes(:,1+2*maxtime:3*maxtime);
stiffr = dcodes(:,1+3*maxtime:4*maxtime);

  endu = -25*ones(numcases,1);
  endd = 53*ones(numcases,1);
  endl = -25*ones(numcases,1);
  endr = 53*ones(numcases,1);
  
  
  % start with zero velocity from the equilibrium position of the initial spring stiffnesses
  velx = zeros(numcases,maxtime);
  posx = zeros(numcases,maxtime);
  posx(:,1)= (endl.*stiffl(:,1) + endr.*stiffr(:,1)) ./ (stiffl(:,1) + stiffr(:,1));
  
  vely = zeros(numcases,maxtime);
  posy = zeros(numcases,maxtime);
  posy(:,1)= (endu.*stiffu(:,1) + endd.*stiffd(:,1)) ./ (stiffu(:,1) + stiffd(:,1));
  
  
  
  % At each subsequent time step, the spring stiffnesses specify an acceleration, 
  % which is converted into a velocity, which is converted into a position.
  for t=2:maxtime
    if varyvisc==1
      viscosities = .15 + .3*(ink(:,t+2)-.5); %%first 2 are for type of ink.
    end;
    accx = (stiffl(:,t).*(endl-posx(:,t-1)) + stiffr(:,t).*(endr-posx(:,t-1)))./masses;
    velx(:,t) = (1-viscosities).*velx(:,t-1)+accx;  
    posx(:,t) = posx(:,t-1)+velx(:,t);
  
    accy = (stiffu(:,t).*(endu-posy(:,t-1)) + stiffd(:,t).*(endd-posy(:,t-1)))./masses;
    vely(:,t) =  (1-viscosities).*vely(:,t-1)+accy;  
    posy(:,t) = posy(:,t-1)+vely(:,t);
  end;
end;