Quick Tips in 3ds Max - Linking Constraint Behavior

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Industry
  • Design Visualization
Subject
  • 2011
  • Basics
Products
  • 3ds Max
Skill Level
  • Beginner
Duration
4 min

Quick Tips in 3ds Max - Linking Constraint Behavior

3ds Max Quick Tips to make you a pro in no time. In this tutorial, learn about the Link Constraint tool and workarounds for irregular behavior.

Notes

  • Recorded in: 3ds Max 2012
  • This tip is intended for use with 3ds Max version 2012 or higher.

Transcript

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If you've used Link Constraint before, you know it's a tool that you use when you want an object to follow multiple parents across time.

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Try a simple example. Create any three primitives in the scene, for example, a teapot in the center and a sphere on either side.

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Select the teapot.

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Say you want the teapot to be a child of the left sphere from frame 0 to frame 50 so that it moves when the sphere moves.

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Starting from frame 50 onward, you want to break that link so that the teapot by that time becomes a child of the sphere on the right.

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After frame 50, the teapot would move when the right sphere moves.

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The process for creating Link Constraint is easy.

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At frame 0, and with the teapot selected, go to Animation > Constraints > Link Constraint.

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A rubber band appears.

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Point it and click on the left teapot.

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The Command Panel switches to the Motion Panel and the teapot is shown as a child of Sphere001 starting at frame 0.

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Go to frame 50.

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You can repeat the menu procedure but it's just as easy to use the Add Link tool to add Sphere002 as a new parent starting at frame 50.

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Right-click or click the Add Link button again to exit that mode.

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Enable Auto Key mode.

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Logically, if you animate the first sphere within its range of control, between 0 and 50,

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and the second sphere between 50 and 100, the teapot should respond to that motion.

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Try it out. Go to frame 20.

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Select Sphere001 and right-click the slider bar to create a position key at frame 20.

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Animate the first sphere between frames 20 and 40, the teapot responds nicely to that motion.

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Similarly, go to frame 60 and select Sphere002.

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Right-click the slider bar to create a position key for that object.

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Animate the second sphere between frames 60 and 80.

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Again, the teapot responds nicely to the behavior of its new parent.

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The problem is that if you are between frames 50 and 100, as is the case right now (at frame 80),

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and you tried to move the first sphere,

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you'll notice that the first sphere is still affecting the teapot, albeit not in a one-to-one ratio.

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The problem is happening because Sphere001 is trying to interpolate between this current keyframe at frame 80,

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and the last one which in this case was at frame 40.

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This interpolation is such that the first sphere is now also moving a little bit between frames 40 and 50,

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before the switch between parents is taking place.

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Between frames 40 and 50, the teapot is still a child of the first sphere and therefore responds to that motion.

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To prevent this behavior from happening, you would need to have better control over the interpolation.

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Go back to frame 0, select the first sphere and delete the keyframe you added at frame 80.

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To control interpolation, you need to ensure that all parents controlling a given object have keyframes when the switch happens.

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In this case, both spheres should have position keyframes at frame 50 to "lock" them in their positions.

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Keep in mind we're only using position keyframes in this example.

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You may need rotation keyframes or other types in a different situation.

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In this case, go to frame 50 and force position keyframes for both spheres.

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From that point on, you won't have any more interpolation problems.
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Tags
  • 3ds Max
  • 2011
  • Basics
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