Microsoft KB Archive/171758

= Microsoft Knowledge Base =

HOWTO: Maintaining A Consistent Background Image
Last reviewed: July 30, 1997

Article ID: Q171758

The information in this article applies to:


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

SUMMARY
This article is provided to show you how to retain a constant view of the background image (relative to camera and scene) when moving or animating the camera by making use of a one joint chain method. To do this, complete the following steps:

 Show the camera. Build a one joint chain and make its length the same as the distance from the camera to the interest. Position constrain (Constrain -> Position) the camera to the root, and the interest to the effector. Get a primitive grid as the backdrop. Position constrain the grid to the effector and then relax the constraint. Constrain it in orientation to the joint and relax the constraint. Add 90 deg. of rotation in the z-axis to make the grid perpendicular to the joint. Make the grid a Child of the joint or local envelope of the chain root.</li> Get a null, constrain it in position and in orientation to the joint and relax both constraints by clicking on the null with the middle mouse button.</li> In Local mode, translate the null slightly above the camera.</li> Select the camera and constrain its up vector to the null.</li> Make the null a Child of the joint.</li>  Scale the grid so that it exceeds the dimensions of your field of view. To properly distance your background away from your elements, select the joint and scale it uniformly. This is an easy way to position your background behind your scene objects without changing its proportions. If you add elements to the scene and you also want them to retain their position relative to the background, make them children of the joint as well. </li></ol>

You can still zoom in and out, as well as dolly your camera back and forth. You should, however, rotate the joint to orbit your camera view as opposed to using the "o" supra key.