eraHelper = new THREE.CameraHelper( shadowCamera );

				// like MeshDepthMaterial, but goes from black to transparent
				depthMaterial = new THREE.MeshDepthMaterial();
				depthMaterial.userData.darkness = { value: state.shadow.darkness };
				depthMaterial.onBeforeCompile = function ( shader ) {

					shader.uniforms.darkness = depthMaterial.userData.darkness;
					shader.fragmentShader = /* glsl */`
						uniform float darkness;
						${shader.fragmentShader.replace(
					'gl_FragColor = vec4( vec3( 1.0