Defining the View (Using MATLAB Graphics)

Using MATLAB Graphics

Example - Dollying the Camera

In the camera metaphor, a dolly is a stage that enables movement of the camera side to side with respect to the scene. The camdolly command implements similar behavior by moving both the position of the camera and the position of the camera target in unison (or just the camera position if you so desire).

This example illustrates how to use camdolly to explore different regions of an image.

Summary of Techniques

This example:

Uses ginput to obtain the coordinates of locations on the image
Uses the camdolly data coordinates option to move the camera and target to the new position based on coordinates obtained from ginput
Uses camva to zoom in and to fix the camera view angle, which is otherwise under automatic control

Implementation

First load the Cape Cod image and zoom in by setting the camera view angle (using camva).

load cape
image(X)
colormap(map)
axis image
camva(camva/2.5)

Then use ginput to select the x- and y-coordinates of the camera target and camera position.

while 1
  [x,y] = ginput(1);
  if ~strcmp(get(gcf,'SelectionType'),'normal')
    break
  end
  ct = camtarget;
  dx = x - ct(1);
  dy = y - ct(2);
  camdolly(dx,dy,ct(3),'movetarget','data')
  drawnow
end

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