Added covers, cross-fade

resources/shaders/fog_shadow_web.fragment

@@ -3,6 +3,7 @@ precision mediump float;
 uniform sampler2D Texture;
 uniform sampler2D uShadowMap;
 uniform vec3 uLightDir;
+uniform float uAlpha;
 
 varying vec2 texCoord;
 varying vec4 fragPosLightSpace;
@@ -72,5 +73,5 @@ void main()
 	float fogFactor = clamp((fogDistance - 30.0) / 10.0, 0.0, 1.0);
 	color.rgb = mix(color.rgb, fogColor, fogFactor);
 
-	gl_FragColor = color;
+	gl_FragColor = vec4(color.rgb, color.a * uAlpha);
 }