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Blendshapes Sample

What does it show?

This sample showscases three objects being deformed using skinning only (left), skinning + blendshapes (middle) and blendshapes only (right) using animation clips.

Note

DOTS blendshape depend on compute shaders to perform mesh deformations. Make sure to add the following scripting define to your project player settings : ENABLE_COMPUTE_DEFORMATIONS. Also, for blendshapes to work, you'll need to create a shader graph that contains a Compute Deformation node (see Assets/Shaders/Basic_Compute_Deformation.shadergraph as an example) which needs to be applied to a material used by the SkinnedMeshRenderer component.

Overview

The entry point to this sample are the root GameObjects defined in the subscene. They hold two important Unity components:

  1. The RigComponent component (from the Unity.Animation package) which defines the rig for the object. During entity conversion, it is converted to a Rig ECS component.
  2. The Blendshapes_ClipPlayer component. This allows you to choose an animation clip to play on the rig. It is converted to a BlendShapes_PlayClipComponent ECS component.

Once converted, several systems run on the cube entity.

  • The BlendShape_PlayClipSystem:
  • For every entity that has a Blendshapes_PlayClipComponent but no Blendshapes_PlayClipStateComponent, it creates an animation graph, and registers it to the PreAnimationGraphSystem from the Unity.Animation package (by adding a tag component to the entity). It then adds a BlendShapes_PlayClipStateComponent to the entity to signal that the graph has been created, and to keep track of this graph (to be able to update and delete it later);
  • For every entity that has both components BlendShapes_PlayClipComponent and BlendShapes_PlayClipStateComponent, meaning the graph was created, if the clip in the BlendShapes_PlayClipComponent has changed the BlendShapes_PlayClipSystem will update the clip used in the graph referenced in the BlendShapes_PlayClipStateComponent;
  • Finally, if the entity has a BlendShapes_PlayClipStateComponent but no BlendShapes_PlayClipComponent, it means the entity was deleted and so the graph is destroyed and the nodes created for this instance are destroyed to avoid a leak. Note that this system is not doing any of the actual computation involved in performing the animation.
  • The PreAnimationGraphSystem executes the graph, and the AnimatedData buffers are updated on the entity by the ComponentNode.

The Animation Graph

The animation graph is using the Data Flow Graph (DFG) to compute an animation. The animation graph is the central concept that drives the animation.

When an animated entity is added, the BlendShapes_PlayClipSystem creates a ClipPlayerNode and a ComponentNode (associated with this entity). It sets up parameters (like the clip to be played) on the ClipPlayerNode by sending it messages. It also connects the output of the ClipPlayerNode to the input of the ComponentNode. This will set the data of the AnimatedData buffer on the entity.

The AnimationGraphSystem from the Unity.Animation package automatically updates the graphs and applies the output to the entity.

Time Management

Each rig entity has a component DeltaTime. This component is updated by the UpdateAnimationDeltaTime system. Using a ComponentNode, the graph connects the value of the DeltaTime component to the converter node ConvertDeltaTimeToFloatNode, and the output of the node is used as an input to evaluate the clip.