I have a rough terrain (plane, displacement mod) that serves as a LAKE. I have an INNER-TUBE (a torus) that I want to tow around on top of the LAKE.

My initial method (that doesn't work, or is incomplete):

  1. Rig: Create a curve. Parent an empty ("BOAT") to the curve in a 'Follow path' relationship. Add a couple of Limit Distance constraints to the INNER-TUBE to create a range of distances the INNER-TIRE can move around the BOAT.

  2. Physics: Create a Rigid Body World. Set LAKE as passive, INNER-TUBE as active. Add some dampening and friction to the LAKE and INNER-TUBE .

  3. Animation: Set frames and negative-start evaluation time for BOAT path (negative start time allows INNER-TUBE to settle on the LAKE before movement). Mark start/finish keyframes for BOAT.

The result is: Not Much. Once BOAT starts moving INNER-TIRE moves with it... but INNER-TUBE is completely unreactive with the TERRAIN, and doesn't swing wide after BOAT turns corners. INNER-TUBE may as well be directly parented to BOAT : INNER-TUBE just stays in the same angle to TRUCK as at the initial orientation.

In short: physics ain't happening.

The scene's enormous so I won't provide a blend file. But if someone could provide a simple .blend that illustrates how to do this boat-tows-inner-tube effect at its simplest level, I'd be grateful :)

  • $\begingroup$ I've never heard it called an "inner-tire" but "inner tube." $\endgroup$ – Geremia Jan 10 '17 at 22:04
  • $\begingroup$ OK... I'll edit :) $\endgroup$ – OroNZ Jan 10 '17 at 22:04

I'm not an expert on rigid body physics in blender, so I can provide a full example, but it sounds like you have used an object constraint to attach the tube to the boat. If you want physics you should use a rigid body constraint instead. See: https://www.blender.org/manual/physics/rigid_body/constraints/types/index.html

  • $\begingroup$ Thanks Sazerac. I was trying rigid body constraints but it turns out I was doing it wrong. After half a day watching YouTube tutorials I saw the error of my ways :) $\endgroup$ – OroNZ Jan 11 '17 at 8:44

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