setup( builder ) {

		if ( this.lights.length === 0 ) {

			this.init( builder );

		}

		return Fn( ( builder ) => {

			this.setupShadowPosition( builder );
			return min( ...this._shadowNodes ).toVar( 'shadowValue' );

		} )();

	}
Sets up the shadow node for rendering.

@param {Builder} builder - The builder used to set up the shadow node.
@returns {Node} A node representing the shadow value.