perf(terrain): cache the vanilla missing-model reference across block renders

MissingModelCompat.isMissingModel walked a four-deep getter chain
(Minecraft -> BlockRendererDispatcher -> BlockModelShapes -> ModelManager)
for every block render during chunk mesh building. The reference only
changes on resource reload, so cache it (volatile, worker-thread safe) and
clear the cache from a reload listener registered in Actinium.onInit.
The one-argument isMissingModel signature is kept so the compat-bridge
renderer bytecode contract is untouched.

Author: DHJComical

src/main/java/com/dhj/actinium/Actinium.java

@@ -3,6 +3,7 @@
 import com.dhj.actinium.compat.chunkanimator.ChunkAnimatorCompat;
 import com.dhj.actinium.compat.dh.ActiniumDHIrisCompat;
 import com.dhj.actinium.compat.dh.DistantHorizonsCompat;
+import com.dhj.actinium.compat.MissingModelCompat;
 import com.dhj.actinium.compat.kirino.KirinoCompat;
 import com.dhj.actinium.compat.neofontrender.NeoFontRenderCompat;
 import com.dhj.actinium.command.TogglePassCommand;
@@ -28,6 +29,7 @@
 import net.coderbot.iris.rendertarget.IRenderTargetExt;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.renderer.OpenGlHelper;
+import net.minecraft.client.resources.IReloadableResourceManager;
 import net.minecraft.launchwrapper.Launch;
 import net.minecraftforge.client.ClientCommandHandler;
 import net.minecraftforge.client.event.RenderGameOverlayEvent;
@@ -175,6 +177,9 @@ public void onInit(FMLInitializationEvent event) {
         ChunkAnimatorCompat.install();
         KirinoCompat.install();
 
+        ((IReloadableResourceManager) Minecraft.getMinecraft().getResourceManager())
+                .registerReloadListener(resourceManager -> MissingModelCompat.onResourceManagerReload());
+
         if ((Boolean) Launch.blackboard.get("fml.deobfuscatedEnvironment")) {
             ClientCommandHandler.instance.registerCommand(new TogglePassCommand());
         }

src/main/java/com/dhj/actinium/compat/MissingModelCompat.java

@@ -25,6 +25,19 @@ public final class MissingModelCompat {
     private MissingModelCompat() {
     }
 
+    /**
+     * Cached vanilla missing-model reference. Resolving it walks a four-deep getter chain through
+     * the block renderer dispatcher, which runs per block render during chunk mesh building; the
+     * reference itself only changes on resource reload, which clears the cache through
+     * {@link #onResourceManagerReload()}. Volatile because chunk meshes are built on worker threads.
+     */
+    private static volatile IBakedModel cachedMissingModel;
+
+    /** Drops the cached missing-model reference so the next check re-resolves it. */
+    public static void onResourceManagerReload() {
+        cachedMissingModel = null;
+    }
+
     /**
      * Binary name of Forge's {@code FancyMissingModel.BakedModel}. The class is package-private,
      * so its name is matched instead of using {@code instanceof}; it ships with Minecraft Forge.
@@ -55,8 +68,12 @@ private MissingModelCompat() {
      * fancy label variant) and must not be rendered from a chunk build worker thread.
      */
     public static boolean isMissingModel(IBakedModel model) {
-        IBakedModel missingModel = Minecraft.getMinecraft().getBlockRendererDispatcher()
-                .getBlockModelShapes().getModelManager().getMissingModel();
+        IBakedModel missingModel = cachedMissingModel;
+        if (missingModel == null) {
+            missingModel = Minecraft.getMinecraft().getBlockRendererDispatcher()
+                    .getBlockModelShapes().getModelManager().getMissingModel();
+            cachedMissingModel = missingModel;
+        }
         return isMissingModel(model, missingModel);
     }