prevent point lights from overflowing shader

EffectInterfaces/PointLightEffect.cs

@@ -2,6 +2,7 @@ namespace Kav
 {
     public interface PointLightEffect
     {
-        PointLightCollection PointLights { get; } // TODO: should be a collection class?
+        int MaxPointLights { get; }
+        PointLightCollection PointLights { get; }
     }
 }

Effects/PBREffect.cs

@@ -117,6 +117,8 @@ namespace Kav
             }
         }
 
+        public int MaxPointLights { get; } = 4;
+
         public PointLightCollection PointLights
         {
             get { return pointLightCollection; }

Renderer.cs

@@ -30,6 +30,7 @@ namespace Kav
                             int i = 0;
                             foreach (var pointLight in pointLights)
                             {
+                                if (i > pointLightEffect.MaxPointLights) { break; }
                                 pointLightEffect.PointLights[i] = pointLight;
                                 i++;
                             }