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Animating a mechanic billboard in Softimage XSI

Start by opening the Billboard.scn scene from this issues CD. The scene contains a bunch of trilons or triangular prisms, 300 to be precise. Using a couple of thousands would obviously be more striking but for the sake of demonstration the number is keep low. While any of the prisms could be used to animate their rotation, it’s a good idea to separate the animation parameters from the actual billboard. Start by selecting the null object named Prisms_Rotation. Press [C] to activate the rotation tool and press [K] to set a keyframe at frame 1. Go to frame 16, rotate the Prisms_Rotation 120 degrees on the Y-axis and set a new keyframe. With the rotation still at 120, set another keyframe at frame 80. Press [0] (zero) to open the Animation Editor and select the function curve for the Y rotation (roty). From the Curves menu choose relative Cycle. To change the pace of your mechanic billboard, just move one of the 3 keyframes.

Press [2] to switch to the Animate toolbar. From the Create > Parameter menu choose New Custom Parameter Set. Enter Billboard as the name and click OK. Press [8] to open an Explorer, select the Billboard parameter set and press [Shift] + [P] to add a new custom parameter. Name the new Parameter Rotation_Delay. The parameter will be used to control the offset of the prisms. Changing the slider will automatically change the delay. The offset is evaluated in seconds; consequently you’re going to use very small values. Change the Maximum Value Range to 0.01 and click OK to close the PPG.

Open an Explorer and select the Prism_No1. Scroll down to Prism_No300 and shift select it to select all the objects in order from 1 to 300. Press [Alt] + [4] to open the Script Editor. Set your script language to Jscript (File > Preferences) and enter the text beneath.

Press the Run button in Script Editor to execute the script. Open the Bilboard PPG and playback the animation while changing the Time_Delay slider.


While the mechanical billboard is outdated at best, your virtual version is just about to start its glory days. Using a simple loop in Jscript adds the expression with the delayed rotation in seconds rather than the frustrating hour required if done manually.

The project files used in this tutorial can be found at:

Quick tip
The order in which the objects are selected also controls the extent of the offset, which in turn is set by Rotation_Delay slider. So, select the object in the order you want them to turn.


  1. May 14, 2009

    Hej Ola!

    Great stuff as always! I think the scene file is from a previous tutorial (frost).

    Keep up the good work!

  2. May 15, 2009

    No idea why Google screwed with my download links in the first place, but I’ve updated the post with their correct links.


  3. May 22, 2009

    Thanks for putting this one up, I like this effect a lot.
    Now for the finisher;
    Is there a way to assign a single bitmap to all of the faces when they line up flat – so each rotation would spin in a new image?

    wayne k
    guam usa

  4. May 26, 2009

    Hi Wayne

    Simply put your objects in a group and apply the texture projecting to the group, then Freeze the objects to “lock the projection”.

    Makes any sense?


  5. August 8, 2009

    – There’s no “large” version of the image where the code is written.
    -The scene file link leads to the frost project.

    I really hope you can fix it, nonetheless, gr8 stuff , thanks a tons !!

  6. August 11, 2009

    I just copied the link and it works now. Thanks a tons !

  7. August 17, 2009

    Hi Sherif,

    I’ve updated the link for the fifth time and it should be working now. I’m experiencing quite a lot of bugs with blogspot, which you’ve noticed, such as incorrect links, post gets completely screwed, images not showing their large version when clicking, etc. A complete redesign is in the works, but it may take quite a while till I get time to finish it…


  8. December 15, 2011

    The link or large picture don’t show up when I click on it….I can’t see the command or script line…please help

  9. December 15, 2011

    Hi Eyad,

    Don’t know why you cant see the images, I have no problem viewing them on my iPhone. Either way , please send me an email and I’ll forward them in an email…