Legacy lighting model is now deprecated (#26683)

src/lights/AmbientLightProbe.js

@@ -11,8 +11,7 @@ class AmbientLightProbe extends LightProbe {
 
 		const color1 = new Color().set( color );
 
-		// without extra factor of PI in the shader, would be 2 / Math.sqrt( Math.PI );
-		this.sh.coefficients[ 0 ].set( color1.r, color1.g, color1.b ).multiplyScalar( 2 * Math.sqrt( Math.PI ) );
+		this.sh.coefficients[ 0 ].set( color1.r, color1.g, color1.b ).multiplyScalar( 2 / Math.sqrt( Math.PI ) );
 
 	}
 

src/lights/HemisphereLightProbe.js

@@ -16,8 +16,7 @@ class HemisphereLightProbe extends LightProbe {
 		const sky = new Vector3( color1.r, color1.g, color1.b );
 		const ground = new Vector3( color2.r, color2.g, color2.b );
 
-		// without extra factor of PI in the shader, should = 1 / Math.sqrt( Math.PI );
-		const c0 = Math.sqrt( Math.PI );
+		const c0 = 1 / Math.sqrt( Math.PI );
 		const c1 = c0 * Math.sqrt( 0.75 );
 
 		this.sh.coefficients[ 0 ].copy( sky ).add( ground ).multiplyScalar( c0 );