A real-time method for generating random-dot motion displays of specified coherence

Author: Intriligator, James

Source: Spatial Vision, Volume 11, Number 1, 1997 , pp. 33-41(9)

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Abstract:

A method that allows the creation of moving random-dot patterns with any desired level of motion coherence is presented. In the present context, a random-dot pattern with 100% coherence is a sliding sheet of dots (all dots move at the same speed and in the same direction). A random-dot pattern with 0% coherence is visual dynamic noise (similar to detuned TV snow). Coherences between 100% and 0% have a specific percentage of the dots moving coherently together, while the remaining 'twinkle' in a random fashion. The use of look-up table animation allows the dot patterns to move smoothly and rapidly even on computers that lack computational speed. Additionally, the coherence of the motion in a particular region of the screen is determined by the spatial arrangement of pixel indices in that local region. Therefore, this technique allows different regions of the screen to have different levels of coherence which makes the creation of motion-defined shapes straightforward. The basics of look-up table animation are discussed and a general algorithm for creating motion with any level of coherence is presented.

Document Type: Research article

DOI: http://dx.doi.org/10.1163/156856897X00041

Affiliations: 1: Department of Psychology, Harvard University, 33 Kirkland Street, Cambridge, MA 02138, USA

Publication date: 1997-01-01

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