How do I add animation to a usd model?

To add animation to a USD model, you can use blend shape animations in Reality Composer Pro. Here's a step-by-step guide based on the information from the WWDC sessions:

Blend Shape Animation:
- Blend shape animations allow you to smoothly transition from one pose to another, creating lifelike movements. These are commonly used for animating a character's face or body by blending between a series of different shapes.
- For example, you can animate a plant from a wilted to a healthy state and vice versa.
Setting Up Blend Shape Animation:
- The blend shape animation API consists of a blend shape weights mapping, blend shape weights component, and two ways to execute the animations: procedurally or via USD animation.
- The blend shape weights mapping allows you to set a weight associated with a blend target. You set up the blend targets on an entity, and each target can have weights associated with it. You can set a weight from zero to one.
Implementing in Code:
- Find the model entity that has the model component from the entity hierarchy.
- Get its mesh resource and create the blend shape weights mapping from the mesh resource.
- Create the blend shape weights component from the mapping.
- To update the blend weights at runtime, get the blend shape weights component from the entity.
- Get a copy of the blend shape weights set to assign weight values into the set.
- Update all the weight values by blend weight index in the blend shape weight set and set it to zero, which indicates a healthy plant.
- To transition from healthy to wilted, gradually increment or decrement the value with an easing function.
- Assign the new weight values to the blend shape weights component so they will take effect.

For a detailed walkthrough, you can refer to the session Compose interactive 3D content in Reality Composer Pro (27:11).

Relevant Sessions:

These sessions provide comprehensive insights into working with USD models and adding animations.