Best way to move multiple objects with a preallocated matrix of coordinates?

Hi,

I want to be able to move multiple objects along a plot of a road or someother way to create an image with previously created coordinate data and I'm not sure what's the best way. I've been trying to see if I can create a patch object and then transform that using hgtransform and makehgtform which is shown in the code below the %=/=/=% line ( the %----% lines are to help indicate sections of code which are functions) but it doesn't transform how I want it to so I'm not sure if it's down to my coding or if it's not suitable. It seems to only transform to the first coordinate and stays there rather than completeing the transition to the final set of coordinates. Advice on where to proceed from this point would be appreciated.

maxCarVelocity=5;
nStarts=2;
nCarsPerStart=100;
deltaT=1;
t=300;

carPosition=carCoords(nStarts,nCarsPerStart);
%--------------------------------------------------------%
function [carPosition] = carCoords(nStarts,nCarsPerStart)
% Creates a matrix of car positions based on their starting locations

%   Creates a NaN matrix and each location( or a lane in the model) has a
%   set number of vehicles generated backwards from the start coord of 0.
%   This is a cumulative sum from a random integer between two values to replicate the
%   semi-random disribution of distance between cars on a road.

carPosition=NaN(nStarts*nCarsPerStart,nStarts);

for i=1:nStarts

carPosition((1:nCarsPerStart)+(i-1)*nCarsPerStart,i)=cumsum([0; randi([-10,-2],nCarsPerStart-1 ,1)]);

end
       
end
%-------------------------------------------------------%
carProperties=intitalCarProperties(nStarts,nCarsPerStart,maxCarVelocity);
%-----------------------------------------------------%
function [carProperties] = intitalCarProperties(nStarts,nCarsPerStart,maxCarVelocity)
% Creates a matrix indicating each car's properties in the simulation.
%   Detailed explanation goes here

% Max car velocity = 30 m/s ~ to 60mph in UK
driverBehaviour=1; % 1 = Normal behaviour
typeOfVehicle=1; %1 = Car (Average 2D dimensions = 4.7m x 1.9m)


carProperties=zeros(nStarts*nCarsPerStart,3);

for i=1:nStarts*nCarsPerStart
    carProperties(:,1)=maxCarVelocity;
    carProperties(:,2)=driverBehaviour;
    carProperties(:,3)=typeOfVehicle;
    
end

end
%------------------------------------------------%
carPosWithTimeStep=repmat(carPosition,1,t+1);

timeSteps = repmat(0:deltaT:t,nStarts,1);
timeSteps = timeSteps(1:end);


for i=1:1:nStarts*nCarsPerStart
    
    for k=nStarts+1:1:nStarts*(t+1)
        
        carPosWithTimeStep(i,k)=carPosWithTimeStep(i,k)+carProperties(i,1)*timeSteps(1,k);
      
    end
end
%=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=/=%
roadLength=1000;

figure('units','normalized','position',[0 0 1 1])

road=plot ([0,roadLength],[7.3,7.3],'k',[0,roadLength],[3.65,3.65],'k--',...
     [0,roadLength],[0,0],'k','linewidth', 1.5);
 axis equal
 
startingXPos1 = [0, 4.5, 4.5, 0];
startingYPos1 = [0.9, 0.9, 2.7, 2.7];
g = hgtransform;
patch('XData',startingXPos1,'YData',startingYPos1,'FaceColor','Red','Parent',g)

for b=1:1:nStarts*nCarsPerStart
    for h=nStarts+1:nStarts:nStarts*(t+1)
        
  g.Matrix = makehgtform('translate',carPosWithTimeStep(b,h)-carPosWithTimeStep(b,h-nStarts),0,0); 
  drawnow
    end
end

Essentially the goal I'm trying to achieve is to create a matrix of coordinate data that I can then plot after to create a moving simulation. Hopefully then I'll be able to create a simulation of a number of cars driving down a road after all the calculations have been done.

[Matt J]

And...what is the problem?

[Jack Smillie]

Sorry, I realised I didn't specify in my post. I'll edit it after this. The transformed patch seems transforms to one coordinate from my preallocated matrix of coordinate data when its plotted and stays there rather than moving across the graph.

The other question was as the title says, what matlab functions would be best to create an object that follows a preallocated matrix of coordinate data?

Answer 1

[Matt J]

I see movement when I do this,

 xl=xlim; 
 for b=1:1:nStarts*nCarsPerStart
    for h=nStarts+1:nStarts:nStarts*(t+1)
            
      pos = carPosWithTimeStep(b,h);
      
          if xl(2)<=pos, break; end
            
      g.Matrix = makehgtform('translate',pos,0,0); 
      drawnow
    end
end

[Jack Smillie]

Thank you, that seems to work. So would proceeding with the hgtransform function be best to model several objects moving at the same time on the same plot?

[Matt J]

It's certainly a valid way, but here, it seems much simpler just to update the patch XData property:

for b=1:1:nStarts*nCarsPerStart
    
    p=patch('XData',startingXPos1,'YData',startingYPos1,'FaceColor','Red');

    for h=nStarts+1:nStarts:nStarts*(t+1)
      
      pos = carPosWithTimeStep(b,h);
      xdelta=pos-carPosWithTimeStep(b,h-nStarts);  
  
      if xl(2)<=pos, delete(p); break; end
 
      p.XData=p.XData+xdelta;
      drawnow
    end
end