getSpotAttenuation( builder, angleCosine ) {

		const iesMap = this.light.iesMap;

		let spotAttenuation = null;

		if ( iesMap && iesMap.isTexture === true ) {

			const angle = angleCosine.acos().mul( 1.0 / Math.PI );

			spotAttenuation = texture( iesMap, vec2( angle, 0 ), 0 ).r;

		} else {

			spotAttenuation = super.getSpotAttenuation( angleCosine );

		}

		return spotAttenuation;

	}
Overwrites the default implementation to compute an IES conform spot attenuation.

@param {NodeBuilder} builder - The node builder.
@param {Node<float>} angleCosine - The angle to compute the spot attenuation for.
@return {Node<float>} The spot attenuation.