const myVarying = varyingProperty( 'vec3', 'myVarying' );

const positionTransformFn = wgslFn( `
	fn positionTransformFn( position: vec3<f32> ) -> vec3<f32> {

		// varyings.* is the structure that will store all the varyings
		// you can use it to access/store your varying value

		varyings.myVarying = position;

		return position;

	}
`, [ myVarying ] );

material = new MeshBasicNodeMaterial();
material.colorNode = myVarying;
material.positionNode = positionTransformFn( { position: positionLocal } );