Added hook to add entity spectator shader

src/main/java/net/minecraftforge/client/ForgeHooksClient.java

@@ -51,12 +51,7 @@ import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 import net.minecraft.tileentity.TileEntity;
-import net.minecraft.util.BlockPos;
-import net.minecraft.util.EnumChatFormatting;
-import net.minecraft.util.EnumFacing;
-import net.minecraft.util.EnumWorldBlockLayer;
-import net.minecraft.util.IRegistry;
-import net.minecraft.util.MovingObjectPosition;
+import net.minecraft.util.*;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 import net.minecraft.world.biome.BiomeGenBase;
@@ -80,6 +75,7 @@ import net.minecraftforge.common.ForgeVersion;
 import net.minecraftforge.common.ForgeVersion.Status;
 import net.minecraftforge.common.MinecraftForge;
 import net.minecraftforge.fml.client.FMLClientHandler;
+import net.minecraftforge.fml.client.registry.ClientRegistry;
 import net.minecraftforge.fml.common.FMLLog;
 
 import org.apache.commons.lang3.tuple.Pair;
@@ -578,4 +574,13 @@ public class ForgeHooksClient
         if(part.isPresent()) return Optional.absent();
         return Optional.of(new TRSRTransformation(matrix));
     }
+
+    public static void loadEntityShader(Class<? extends Entity> entityClass, EntityRenderer entityRenderer)
+    {
+        ResourceLocation shader = ClientRegistry.getEntityShader(entityClass);
+        if (shader != null)
+        {
+            entityRenderer.loadShader(shader);
+        }
+    }
 }

src/main/java/net/minecraftforge/fml/client/registry/ClientRegistry.java

@@ -12,6 +12,9 @@
 
 package net.minecraftforge.fml.client.registry;
 
+import com.google.common.collect.Maps;
+import net.minecraft.entity.Entity;
+import net.minecraft.util.ResourceLocation;
 import org.apache.commons.lang3.ArrayUtils;
 
 import net.minecraft.client.Minecraft;
@@ -21,8 +24,12 @@ import net.minecraft.client.settings.KeyBinding;
 import net.minecraft.tileentity.TileEntity;
 import net.minecraftforge.fml.common.registry.GameRegistry;
 
+import java.util.Map;
+
 public class ClientRegistry
 {
+    private static Map<Class<? extends Entity>, ResourceLocation> entityShaderMap = Maps.newHashMap();
+
     /**
      *
      * Utility method for registering a tile entity and it's renderer at once - generally you should register them separately
@@ -47,4 +54,21 @@ public class ClientRegistry
     {
         Minecraft.getMinecraft().gameSettings.keyBindings = ArrayUtils.add(Minecraft.getMinecraft().gameSettings.keyBindings, key);
     }
+
+    /**
+     * Register a shader for an entity. This shader gets activated when a spectator begins spectating an entity.
+     * Vanilla examples of this are the green effect for creepers and the invert effect for endermans.
+     *
+     * @param entityClass
+     * @param shader
+     */
+    public static void registerEntityShader(Class<? extends Entity> entityClass, ResourceLocation shader)
+    {
+        entityShaderMap.put(entityClass, shader);
+    }
+
+    public static ResourceLocation getEntityShader(Class<? extends Entity> entityClass)
+    {
+        return entityShaderMap.get(entityClass);
+    }
 }