3D Studio Max 1.x Expression Problems

By Alex Kiriako, Associate Editor, 3D Artist

Expressions are a powerful part of Kinetix 3D Studio Max release 1.0. However, this feature has some limits and bugs. Here are some tips and tricks to get familiar with using them. Our thanks for help in clarifying these problems and workarounds goes to Randy Kreitzman, in quality control at [the former] Kinetix, and to author Michael Koch, who's article on slider expressions in 3D Artist #28 sparked this report. If you have suggestions or can give accurate descriptions of other types of expression problems, please contact 3DS Max tech support.

Known Bugs

All of the following problems are on the Kinetix fix list for 3D Studio Max release 2, which [at the time of this article had] not yet been formally announced.

If you have one or more selected keys in Track View for an expression, you won't be able to access that expression's properties by right-clicking on it. Under these circumstances, properties will not be highlighted in the popup.
___ The trick around this bug is to simply left-click in the right panel of Track View, which deselects all currently selected keys.

Creating links between objects using expression controller variables assigned to transform controllers (such as position, rotation, and scale) can cause problems when any of the linked objects are placed into groups.
___ This problem occurs because these types of assigned variables report their positions as offsets relative to their parent object, not as absolute values in world space (relative to [0,0,0]). So one object variable dependent on another object will change its position when that other object becomes part of a group. The net effect is that an object may jump to a new position upon the grouping and ungrouping of its parents.

In the Expressions dialog, reassigning a variable that is already assigned to a controller sometimes will not show the new update correctly in the label below the Scalars and Vectors windows. This label sometimes will report an incorrect node name if a variable is assigned to the controller of a child object. This problem becomes visible as soon as the scene is saved. (This doesn't affect anything, it's just a pain.) [screen shot]

That's it for the bugs and fixes. Below is a wish list for changes to 3DS Max's expressions feature that have been posted to Kinetix.

Wish List

  1. The ability to assign variables to the Tick Offset field which would allow access to the position coordinates of a given object at a variable time t. Right now you can only get the current or shifted time.
  2. Variable assignments should be able to be saved to .XPR files, not just the names. Right now only names are saved. So, when you want to assign the saved expressions to other objects, they must manually be reassigned. Usability would greatly be enhanced if this there was an option for optional automatic reassignment upon loading.
  3. The ability to define intermediate results as named variables. This type of macro capability could then be used in expressions thereby helping greatly with readability.

More About Expressions

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Revised: 13 Sep 00
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