In this YouTube video, Dominiek de Ridder quickly demonstrates animating a ball travelling through a pipe in a cartoon-like way, where the pipe bulges out much like a snake swallowing a mouse.

However cool and simple it looked, I just could not get it to work following his simplistic instructions. I even challenged a few other modonauts to watch his video and try to replicate it, but none of them were successful. So then I was determined to try and figure it out myself.

In the end I think it took me around 30 hours over a three week period, no exaggerating! Looking back it looks pretty straightforward - with the help of hindsight. So if you think you are clever, go watch his video first and when you confess you cannot do it in the first 30 minutes, then come back here and follow my instructions and I'll guarantee you'll get it done in under 20 minutes. So, are you up for the challenge? And no cheating either.

Create a pipe, a ball and a curve

• From the Left viewport, shift-click a Cylinder
• Scale the cylinder 200% on the Y, and move it up so that its base sits at 0
• Press N to create a new Item. Select Curve from the modo tools menu and click just below the center-base of the cylinder and continue to create a curve of 6-8 segments and ending just above the top of the cylinder.
• Rename that mesh item to Curve. Make sure the curve is centered on X/Z (eyeball it from the Top).
• Parent the Curve to the Cylinder by dragging the Curve onto the Cylinder item
• Shift-click a new Sphere shape and move it down just below the cylinder where the Curve starts

Deform Cylinder with Bend Deformer

• From the Animate tab (along the top), select the Cylinder and the Curve
• Under the Deformer tab on the left, click on Bend
• Reposition the Bend Deformer (using the W key) so that it starts at the base of the cylinder.
• From the Properties menu on the right, under the Bend Effector, using the <> arrow keys, increase the length of the deformer to cover the entire length of the cylinder.
• Increase the angle to 90 degrees and the cylinder will bend over.

Apply Magnet to the Cylinder

• Again selecting the Cylinder, from the Deformers tab, click on Magnet
• Check the Repulsive box. This will make the cylinder expand rather than contract when the sphere passes through it.
• Resize the diameter of the Magnet Effector under Range to suit the amount you want the cylinder to bulge
• Reposition the Magnet Effector so that it surrounds the sphere
 



Parent the Sphere to the Magnet Effector

• In the Item list, drag the Sphere over the Magnet Effector

 

Constrain the Magnet Effector to the Curve

• Select the Magnet Effector, and then Ctrl-click on the Curve so that both are selected
• Under the Commands menu on the left, select > Modifiers > Constraints > Path > Path Position

 



 

Note: Even though a Path Constraint can also be found under the Animate tab at the top - don't use it! It doesn't work.



Animate the Sphere

• From the Items List, under the Magnet Effector, select the Path Constraint: Curve
• At Keyframe 0, set the Path Percentage in the Properties tab to 0%, and right-click the Channel and Set Key (orange circle will appear)
• At Keyframe 30, set the Path Percentage at 100%, right-click the channel and Set Key