Final answer:
At least two cameras are necessary for 3D motion analysis, as they allow for triangulation of positions for accurate reconstruction, but more cameras are typically used to capture multiple angles and improve accuracy.
Step-by-step explanation:
For 3D analysis in human motion, typically multiple cameras are utilized for accurate capture of movements. Although the exact number can vary by system, at least two cameras are generally required. This is because 3D motion capture systems need to triangulate the position of markers or points from different angles to reconstruct the three-dimensional coordinates. However, for more complex analyses or to improve accuracy, it's common to use more than two cameras, often arranged in a setup that encompasses multiple angles around the moving subject. Thus, while two is the minimal for strictly 3D reconstruction, using four or more cameras is very common in the industry.