Add a option to disable occlusion check.

src/minecraft/net/minecraft/src/EntityPlayer.java

@@ -478,7 +478,7 @@ public abstract class EntityPlayer extends EntityLiving implements ICommandSende
      */
     public void onLivingUpdate()
     {
-    	System.out.println((worldObj.isRemote ? "Client" : "Server") + " position: " + posXBig.toPlainString());
+//    	System.out.println((worldObj.isRemote ? "Client" : "Server") + " position: " + posXBig.toPlainString());
         if (this.flyToggleTimer > 0)
         {
             --this.flyToggleTimer;

src/minecraft/net/minecraft/src/RenderGlobal.java

@@ -18,7 +18,8 @@ import org.lwjgl.opengl.GL11;
 
 public class RenderGlobal implements IWorldAccess
 {
-    public List tileEntities = new ArrayList();
+    private static final boolean DISABLE_OCCLUSION_CHECK = Boolean.getBoolean("net.minecraft.src.DISABLE_OCCLUSION_CHECK");
+	public List tileEntities = new ArrayList();
     private WorldClient theWorld;
 
     /** The RenderEngine instance used by RenderGlobal */
@@ -153,7 +154,7 @@ public class RenderGlobal implements IWorldAccess
         byte var3 = 34;
         byte var4 = 32;
         this.glRenderListBase = GLAllocation.generateDisplayLists(var3 * var3 * var4 * 3);
-        this.occlusionEnabled = OpenGlCapsChecker.checkARBOcclusion();
+        this.occlusionEnabled = !DISABLE_OCCLUSION_CHECK && OpenGlCapsChecker.checkARBOcclusion();
 
         if (this.occlusionEnabled)
         {