..::escalator steps::..

Creating the steps is not really a problem, it's just a simple case of basic modelling. The step it'self is just a simple segment spline that has been extruded. Add any additional detail you may wish to now, or later if you instance-copy the step, therefore allowing you to modify the original step and every other copied step.

The animation of the step can be derived from using a Path motion controller. Create a spline exactly how you would imagine your Escalator's shape would be; namely flat at the bottom and top so people can get on and off, with a slight dip before and after the flat parts on the bottom and top accordingly so the step moves up and dips down at the beginning and end of it's motion. Assign a path motion controller to the step object and rotate it if required to align it with the path. Ensure Constant Velocity is checked on, else the step will speed up and slow down.

By scrubbing the timebar, the step will be seen to be moving up the spline path over the 100 frames, although we need this to repeat, else we will have to copy more steps (this is not necessary, and will give you more control over step placement, although geometry count and setup time will be greater).

In Track View, expand the step object's Transform controller until you get to the Percent controller. View the properties of the end percentage key and change the Value form 100 to 200 (or 300 if you wish them to loop more), so the step's motion loops over the 100 frames. We now need to instance-clone the step object another 10 or so times. Scrubbing the timebar again should show all the steps moving together, therefore we need to amend the start and end times of each step's motion.

Back in Track View, select the second step and move the start and end percent keys back about two or three frames. If you do this while viewing a viewport window, you will notice that the second step object moves back along the spline path and slightly intersects the step in front of it; this is the type of effect we are after, so repeat the process for the other steps, moving the keys back a few frames with respect to the previous step's keys. Once all the step object's keys have been offset against each other, create the bottom and top platforms to hide the loop.

Scrubbing and / or playing back the animation will reveal that the steps are moving way to fast for anyone to stand on them safely! Therefore, increase the number of frames in the animation (or scale it). You may also want to and add more steps. Due to this method, you may find that the 1st and last step are closer together or further apart than the others, in which case, remove the looping and add more step objects to fill in the gaps the removal of the loop has left behind.

If none of this is for you, then for a small fee, StairMax from Cebas Computer (www.cebas.com) will happily do the job for you!

	Offset each step by a few frames, with respect to the previous one, to get the staggered path animation effect.
	Each step's motion path is a spline that has the two flat landings with a slight dip. Occlude the loop with platform geometry.

Initially published: 3D World magazine, Issue 9, February 2001.

Copyright © Pete Draper, February 2001. Reproduction without permission prohibited.

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