is* adjustment

src/scenes/Fog.js

@@ -6,8 +6,6 @@ class Fog {
 
 		this.name = '';
 
-		this.isFog = true;
-
 		this.color = new Color( color );
 
 		this.near = ( near !== undefined ) ? near : 1;
@@ -34,5 +32,6 @@ class Fog {
 
 }
 
+Fog.prototype.isFog = true;
 
 export { Fog };

src/scenes/FogExp2.js

@@ -5,7 +5,7 @@ class FogExp2 {
 	constructor( color, density ) {
 
 		this.name = '';
-		this.isFogExp2 = true;
+
 		this.color = new Color( color );
 		this.density = ( density !== undefined ) ? density : 0.00025;
 
@@ -29,5 +29,6 @@ class FogExp2 {
 
 }
 
+FogExp2.prototype.isFogExp2 = true;
 
 export { FogExp2 };

src/scenes/Scene.js

@@ -7,7 +7,6 @@ class Scene extends Object3D {
 		super();
 		this.type = 'Scene';
 
-		this.isScene = true;
 		this.background = null;
 		this.environment = null;
 		this.fog = null;
@@ -55,5 +54,6 @@ class Scene extends Object3D {
 
 }
 
+Scene.prototype.isScene = true;
 
 export { Scene };