In this research, we propose an accurate calculation method of optical flows caused by movement of a viewpoint on a perspective projection. We developed a tool to calculate optical flows in a pixel unit at high-speed by using projective texture technique. We began by clarifying the optical flow of four types of walls by changing the arrangement angle against the moving direction of a viewpoint. In a simple case study of five types of corridors, we confirmed to measure some spatial indices (averaged optical flow, contact time to the object, appearing and disappearing rate of a visible wall at occluding edges) for analyzing the extent or closeness of a space from a viewpoint. As a characteristic of optical flow, a part of a positive change was seen next to that of a negative change in the opening.

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