Tests were performed to relate the distance from the patient to the camera with the size of virtual arm to be drawn.
After gathering a few values,
it was observed that the square root of the area of the face decreases linearly with the increasing distance between the subject and the camera. We used a spreadsheet to calculate the formula with the lowest error rate detected between distance and actual distance. Figure 8 shows the measured values and the trend line generated. This curve is dependent on the camera used because changing the viewing angle of the lenses result in a differential area size of the face in the image, while maintaining a fixed distance. Therefore, the values are defined in an external camera setup.