如何在Matlab中实时绘制3D点？

Question

I am confused on the best way to implement plotting 3D points live in Matlab. One idea I had is to keep updating an array of x,y,z values and then plot that, but I want it to plot live, as I'm using a LiDAR scanner for a project and want to show a 3D map being created. This is the example I've been trying to work off of:

x = rand(10,1) ; y = rand(10,1) ;
h = scatter(x,y,'Or') ;
for i = 1:100
    x = rand(10,1) 
    y = rand(10,1) ;
    set(h,'XData',x,'YData',y) ;
    drawnow
    pause(0.1)
end

I have one problem with this, and it persists when I move to adding a Z value as well. The plotting works, even in 3D, but then every iteration of the loop removes all of the previous points and then replaces them with the new points. As I'm making a map, I need the points to be maintained with maximum efficiency.

So, I'm wondering if there is a way to plot in real time without having to plot the entire thing over and over again, instead just "appending" the points onto the 3D plane. If there isn't, I would want to know how to fix my code so that points will not be replaced.

Answer 1

Instead of set(h,'XData',x,'YData',y) ; , hold on with new plot could enable you append something onto the plane, so the code following might work:

x = rand(10,1) ; y = rand(10,1) ;
h = scatter(x,y,'Or') ;
hold on      % allow appending
for i = 1:100
    x = rand(10,1) 
    y = rand(10,1) ;
    h = scatter(x,y,'Or') ;   %draw new points
%     set(h,'XData',x,'YData',y) ;
    drawnow
    pause(0.1)
end

But keeping all datas, such as saving new statistics into a new column which is just behind the old ones, is highly recommended:

[x,y] = deal(zeros(10,100));           %pre-allocate
figure(1); hold on
for ii = 1:100
    x(:,ii)=rand(10,1);                %save new x
    y(:,ii)=rand(10,1);                %save new y
    scatter(x(:,ii),y(:,ii),'Or') ;    %plot them
    drawnow
    pause(0.1)
end

Moreover, hold on has downside sometimes when we need further editing the figure by dealing with the handle, as every ten points would have unique handle. To keep them all in one, I think a minor change to your code might be a better solution if we don't have too much data to plot(It demands re-allowcate vectors in RAM, 'clean' the figure, and replot all the points, including those old one, again and again).

x = rand(10,1) ; y = rand(10,1) ;
h = scatter(x,y,'Or') ;
for i = 1:100
    x(end+1:end+10) = rand(10,1) ;     % append x
    y(end+1:end+10) = rand(10,1) ;     % append y
    set(h,'XData',x,'YData',y) ;       % draw new figure
    drawnow
    pause(0.1)
end