Automating with Expression controllers

- [Narrator] In computer graphics an expression…is some sort of mathematical equation that drives…some value and in 3DS Max the program module…that creates movement or animation is a controller.…In 3DS Max one way to apply an automated movement…or rotation or parameter change is through…an expression controller, and in this case,…we'll use an expression controller to drive…the rotation of a ball based upon its position,…so that the ball will roll across a floor.…

And thinking ahead, I want to link the ball…to a control object, so that then I can position…and rotate that control object in order…to direct the trajectory of the ball.…I've got my ball all ready here at the origin.…Let's create a helper object and link the ball to that.…I'll turn on 3D snaps, and I'm snapping to the grid points.…We can just check that by right clicking on the magnet…and snaps are set to grid points only.…

Go over to the create panel in the helpers section…and click on point and then just click at the origin…to create that point helper.…