Sunday, February 17, 2008

Truly DIY Bullet Time

The winner of Instructables' Laser Cutter Contest was "DIY Bullet Time". Unfortunately, in this case DIY means "only costs $5000-$8000 and takes just two days".

The difficulty of capturing bullet time images is that it requires a number of simultaneous perspectives, and each perspective implies a light capturing mechanism and storage device. In this case, each perspective is filled by a separate camera.

What if we combined the perspectives and captured them in parallel? For example: set up a network of mirrors and lenses to redirect the light from each perspective into a matrix/2D-grid that is projected onto the lens of a single camera. The main limitation of this approach would be that certain configurations are much easier to construct than others.

Another possibility: use a microcontroller to process the images from multiple cheap webcams and send them via USB to a computer for storage. USB runs at 480Mbits/s, or 16Mbits/frame at 30 fps (more likely 32Mbits/frame since cheap webcams are still in the 15 fps range). This allows for up to 16 uncompressed 1 megapixel (640x480 pixel) frames in parallel. The number of perspectives is probably more limited by the speed of the microcontroller than the USB speed. Total price would be two orders of magnitude lower than the Instructable, in the range of $120 if 16 cameras at $6 each and some electronics coming to less than $20 are used.

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