Automatically disable and re-enable Optifine's Fast Render setting before rendering a video

src/main/java/com/replaymod/compat/optifine/OptifineReflection.java

@@ -0,0 +1,27 @@
+package com.replaymod.compat.optifine;
+
+import net.minecraft.client.settings.GameSettings;
+
+import java.lang.reflect.Field;
+
+public class OptifineReflection {
+
+    // GameSettings.ofFastRender
+    public static Field gameSettings_ofFastRender;
+
+    static {
+        try {
+            // this throws an ignored ClassNotFoundException if Optifine isn't installed
+            Class.forName("Config");
+
+            gameSettings_ofFastRender = GameSettings.class.getDeclaredField("ofFastRender");
+            gameSettings_ofFastRender.setAccessible(true);
+        } catch (ClassNotFoundException ignore) {
+            // no optifine installed
+        } catch (NoSuchFieldException e) {
+            // the field wasn't found. Has it been renamed?
+            e.printStackTrace();
+        }
+    }
+
+}