writeShapeValues method
Gives values what shapeKey is made from, one by one, so a renderer
can tell each frame whether the mesh changed without making a key.
A shape of the engine's gives plain numbers; the default gives
shapeKey itself.
Implementation
@override
void writeShapeValues(ShapeValues values) => values
..add(radius)
..add(tubeRadius)
..addInt(segments)
..addInt(sides)
..addBool(smooth);