I’ve got a bunch of cardboard cut-out trees & people. I want them to pivot to face the camera during my flythrough, but my camera goes up in the air sometimes & I don’t want them to pivot in the z-axis. Basically, I want them to function like the tree components in Sketchup. The 3ds Max look-at constraint won’t let me lock in the z-axis. Is there a way to get them to pivot the way I want them to?

You can link a dummy to the X&Y position of the camera, then have the trees look at that.
Here’s a video tutorial: Link

3ds Max 2009 SP1, 2010 SP1
Maya 2012
Windows 7 Professional 64-bit
Dual Intel Xeon E5520, 6 GB Ram
NVIDIA GeForce GTX 460 OC

That will work, and it is useful to know about wire parameters.
Here is another method.

1. Create and position your Camera.
2. Create a Dummy and Align the Dummy to the Camera using Pivot to Pivot and Align Orientation on X, Y, and Z.
3. Select all the objects you want to look at the Camera and assign a Look at Constraint; Pick the Dummy for the look at object.
4. Position the Dummy for the desired effect. In your case move the Dummy in World Z.
5. Link the Dummy to the Camera.
6. With the Dummy selected, go to the Hierarchy panel: Link Info, and turn off Inherit Move: Z.

Now you can move your Camera, the objects will always look at the Dummy, but never look up or down.

If I wanted the objects to look at the Camera, but at only 25% of its absolute Z Position value, then Wire Parameters would be the way to go. You wire the X and Y of the Dummy to the Camera, and wire the Z of the Dummy to the Camera with an Expression of Z_Position/4

Now the objects will look at the Camera, but only at 25% of the Camera’s Z value.

Tim Wilbers [FA]

College of Arts and Sciences
Department of Visual Arts
University of Dayton
http://www.udayton.edu/
3ds Max: 7.5, 8, 9, 2008, 2009, 2010

What if your trees are not on the same Z plane? On the side of a hill for example?

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1. Pick all the objects to look at the Dummy.
2. Go to the Hierarchy Panel: Pivot.
3. Click on Affect Pivot Only.
4. Choose Align from the Main Toolbar.
5. Pick the Dummy object, and align Position in the axis that moves the pivots of the objects to the same World Z value as the pivot of the Dummy.
6. Turn off Affect Pivot Only
7. With all the objects selected, assign the Look at Constraint and pick the Dummy for the LookAt Target.
8. Adjust the LookAt Axis and aligned to Upnode Axis as needed in the Motion Panel.

Tim Wilbers [FA]

College of Arts and Sciences
Department of Visual Arts
University of Dayton
http://www.udayton.edu/
3ds Max: 7.5, 8, 9, 2008, 2009, 2010

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Works a treat. Thanks.
What about the PFlow ShapeFacing operator? Is it going to be necessary to script the pivot?

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