Wednesday, April 7, 2010

Structured light - First experiment

An approach to the problem of scanning objects to 3D geometry is using a technique known as structured light. Kyle McDonald's instructable  clearly explains the steps needed to create a scan using this technique. The program necessary is available on google code.

Since this is a potential technique for our project, a good start would be to reproduce the experiment in  ideal conditions.
These conditions are:
  • Good lighting on the scene (only illuminating the target object)
  • Perfect camera orientation
  • A simple object to be scanned
Although structured light is robust enough to make successful scans in less strict conditions, it seems useful to have an idea of what are the best results we can expect. This can only be done in ideal conditions.

The experiment consisted of simulating the camera, projector and target object in a 3D software to generate three images. Then, using these images and the ThreePhase applet found in the google code project mentioned above, retrieve the 3D geometry.
A simple cone was used as the target object. The projector was simulated using a spot light with a projection map looking at the object in the exact same direction as the camera.
The scene was rendered three times to a bitmap using three different patterns as projector map. Said patterns can be found in the project folder. as projector map. Finally, the applet was used with these three renderings and the 3D geometry is retrieved as a cloud of points.

Experiment deployment

The first results were not ideal due to the projector and camera having the same location. Hence, the pattern projected on the target object was undeformed and no depth information could be retrieved.
To correct this, the projector was pulled away from the camera and the experiment was repeated twice using different distances.
The best results were obtained using the experimental setup shown above.

The acquired results can be used in next stages of the project as a starting point to create 3D Meshes from clouds of points.

The collected renderings using the three patterns:

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