Microsoft KB Archive/167242

= Microsoft Knowledge Base =

INFO: Converting The SOFTIMAGE 3D Camera Angle
Last reviewed: April 22, 1997

Article ID: Q167242

The information in this article applies to:


 * Softimage 3D for IRIX, versions 3.0, 3.5, 3.51, 3.7
 * Softimage 3D for Windows NT, versions 3.0, 3.01, 3.51, 3.7

SUMMARY
By design, the SOFTIMAGE 3D camera custom angle is the vertical angle and not the standard lens angle (which is the horizontal angle). When you use the SOFTIMAGE 3D camera data (usually for tracking purposes), you must first convert the vertical angle to the horizontal angle and then use the resulting data. If you use the camera data before converting it, with the assumption that the angle is on the horizontal, the resulting scene images will appear distorted. To avoid this problem, use the following conversion formula:

  If you have the vertical angle and the aspect ratio, to find the horizontal angle, apply the two known values to the following formula: Horizontal = 2 * arctan (aspect * tan(Vertical / 2) 

-or-

  If you require the vertical angle, and know the horizontal value and the aspect ratio, apply the two known values to the following formula: Vertical = 2 * arctan (tan(Horizontal / 2) / aspect) 