Project 3d: Dynamics

Goal Learn the basics of Rigid Body Dynamics.

Another form of procedural animation is Rigid Body Dynamics. As the name implies, this system deals with objects that do not change in shape, as opposed to a system like nCloth that deforms the input mesh. You can think of Rigid Body Dynamics as a physics simulation that calculates how objects should react when they collide. This can be useful when you have too many objects to animate by hand. We will be using the Dynamics menu set for this project.

  1. As with nCloth, we will briefly demonstrate the power of Dynamics. Create a plane and a wall of 25 cubes. Make sure that the objects do not intersect each other as this will cause problems with the simulation. Select the plane and go to Soft/Rigid Bodies → Create Passive Rigid Body. Select the cubes and go to Soft/Rigid Bodies → Create Active Rigid Body. With the cubes selected, create a new gravity field (Fields → Gravity). This will link the gravity to the cubes.

    If you play the simulation, the results will probably be unexciting. Add a sphere and make it an active rigid body. In the Attribute Editor of the rigidBody node of the sphere, under Initial Settings, adjust the Initial Velocity so that the sphere collides with the wall. You can cache the result by going to Solvers → Memory Caching → Enable.

  2. For the next part of this assignment, we will be using the following script to set up a domino course. First create a curve using the CV Curve Tool to lay out the path of your dominoes. Paste the script into your Script Editor (Window → General Editors → Script Editor) and with the curve selected do Command → Execute. This will create a set of dominoes with the first one already falling over.

    The dominoes are not dynamic yet, so select them all and make them active rigid bodies. Link your gravity field to the dominoes by selecting them both and going to Fields → Affect Selected Object(s). Hit play and watch them fall down.

    Eventually you are going to want more control over the motion of your dynamic objects. A rigid body simulation is a good starting point, but there will be a lot of motion you will need to clean up. To do this, you can convert your dynamics into a set of key frames by going to Edit → Keys → Bake Simulation (Options). You will want to specify how many frames you want to bake out. Once you are finished tweaking your dominoes, turn in a playblast of them falling down.

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