Mouse interaction with meshes in matlab

Alec Jacobson

December 30, 2010

weblog/

Here's a small piece of code illustrating how to receive mouse clicks on a mesh plotted with trisurf in matlab. Assuming your mesh is stored with vertices in V and face indices in F, then have onmeshdown be the function you want to be called when the mesh is clicked and onvoiddown be the function you want to be called when the void in the plot outside the mesh is clicked (the white and the grey parts).

tsh = trisurf(F,V(:,1),V(:,2),V(:,3),'tag','trisurf','ButtonDownFcn',@onmeshdown);
p = get(tsh,'Parent');
set(p,'ButtonDownFcn',@onvoiddown);

Here's a little demo showing you what you can do with that:

function dragdemo(V,F)
  figure 
  tsh = trisurf(F,V(:,1),V(:,2),V(:,3),'ButtonDownFcn',@onmeshdown);
  p = get(tsh,'Parent');
  set(p,'ButtonDownFcn',@onvoiddown);
  view(2);
  axis equal
  axis manual
  down_pos = [];
  drag_pos = [];
  down_V = [];

    function onvoiddown(src,ev)
      % do nothing
    end

    function onmeshdown(src,ev)
      down_pos=get(gca,'currentpoint'); 
      title(sprintf('(%1.0f,%1.0f)',down_pos(1,1,1),down_pos(1,2,1)));
      set(gcf,'windowbuttonmotionfcn',@drag) 
      set(gcf,'windowbuttonupfcn',@up)
      down_V = get(tsh,'Vertices');
    end

    function drag(src,ev)
      drag_pos=get(gca,'currentpoint'); 
      title( ...
        sprintf( ...
          '(%1.0f,%1.0f) -> (%1.0f,%1.0f)', ...
          down_pos(1,1,1),down_pos(1,2,1), ...
          drag_pos(1,1,1),drag_pos(1,2,1)));
      set( ...
        tsh, ...
        'Vertices', ...
        [ ...
          (drag_pos(1,1,1) - down_pos(1,1,1)) + down_V(:,1), ...
          (drag_pos(1,2,1) - down_pos(1,2,1)) + down_V(:,2), ...
          down_V(:,3) ...
        ]);
    end

    function up(src,ev) 
        set(gcf,'windowbuttonmotionfcn',''); 
        set(gcf,'windowbuttonupfcn',''); 
    end

end