Hi all, I have created a mod with a 3D model that I created in Techne. Then I added this 3D model to my mod, with this code:

MinecraftForgeClient.registerItemRenderer(Gun.itemID, new ItemRenderP90());

This code works when I launch the client, but when I launch the server, I get this error:

cpw.mods.fml.common.LoaderException: java.lang.NoClassDefFoundError: net/minecraft/client/multiplayer/WorldClient
    at cpw.mods.fml.common.LoadController.transition(LoadController.java:147)
    at cpw.mods.fml.common.Loader.loadMods(Loader.java:515)
    at cpw.mods.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:85)
    at cpw.mods.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:347)
    at net.minecraft.server.dedicated.DedicatedServer.startServer(DedicatedServer.java:69)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:431)
    at net.minecraft.server.ThreadMinecraftServer.run(ThreadMinecraftServer.java:16)
Caused by: java.lang.NoClassDefFoundError: net/minecraft/client/multiplayer/WorldClient
    at net.minecraftforge.client.MinecraftForgeClient.getStencilBits(MinecraftForgeClient.java:64)
    at net.minecraftforge.client.MinecraftForgeClient.<clinit>(MinecraftForgeClient.java:68)
    at mods.Gunscraft.mod_Gunscraft.preinit(mod_Gunscraft.java:181)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at cpw.mods.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:494)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)
    at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)
    at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314)
    at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)
    at com.google.common.eventbus.EventBus.post(EventBus.java:267)
    at cpw.mods.fml.common.LoadController.sendEventToModContainer(LoadController.java:192)
    at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:172)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)
    at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)
    at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314)
    at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)
    at com.google.common.eventbus.EventBus.post(EventBus.java:267)
    at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:103)
    at cpw.mods.fml.common.Loader.loadMods(Loader.java:514)
    ... 5 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.multiplayer.WorldClient
    at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:238)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 35 more
Caused by: java.lang.RuntimeException: Attempted to load class net/minecraft/client/multiplayer/WorldClient for invalid side SERVER
    at cpw.mods.fml.common.asm.transformers.SideTransformer.transform(SideTransformer.java:50)
    at cpw.mods.fml.relauncher.RelaunchClassLoader.runTransformers(RelaunchClassLoader.java:352)
    at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:225)
    ... 37 more

If I delete "MinecraftForgeClient.registerItemRender" code, the server works.

Thanks!

That is a client only method, you have to call it through a proxy.