From f2aae3ef0fe952ee60a89e9bea44444c9be9a473 Mon Sep 17 00:00:00 2001
From: Sebastian Hartte <sebastian@hartte.de>
Date: Tue, 8 Sep 2020 17:56:02 +0200
Subject: [PATCH] Added a global Voxelshape cache for cable bus voxel shapes,
 since combining voxel shapes turns out to be an extremely expensive process
 (i.e. 1.7s for 10000x5 shapes).

---
 .../java/appeng/parts/CableBusContainer.java  |  8 +-
 .../java/appeng/parts/VoxelShapeCache.java    | 81 +++++++++++++++++++
 2 files changed, 82 insertions(+), 7 deletions(-)
 create mode 100644 src/main/java/appeng/parts/VoxelShapeCache.java

diff --git a/src/main/java/appeng/parts/CableBusContainer.java b/src/main/java/appeng/parts/CableBusContainer.java
index b2ddc03fb..a48f602c9 100644
--- a/src/main/java/appeng/parts/CableBusContainer.java
+++ b/src/main/java/appeng/parts/CableBusContainer.java
@@ -41,7 +41,6 @@ import net.minecraft.util.Hand;
 import net.minecraft.util.math.AxisAlignedBB;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.shapes.VoxelShape;
-import net.minecraft.util.math.shapes.VoxelShapes;
 import net.minecraft.util.math.vector.Vector3d;
 import net.minecraft.world.IBlockReader;
 import net.minecraft.world.World;
@@ -82,7 +81,6 @@ public class CableBusContainer extends CableBusStorage implements AEMultiTile, I
     private final EnumSet<LayerFlags> myLayerFlags = EnumSet.noneOf(LayerFlags.class);
     private YesNo hasRedstone = YesNo.UNDECIDED;
     private IPartHost tcb;
-    // TODO 1.10.2-R - does somebody seriously want to make parts TESR??? Hope not.
     private boolean requiresDynamicRender = false;
     private boolean inWorld = false;
     // Cached collision shape for living entities
@@ -1096,11 +1094,7 @@ public class CableBusContainer extends CableBusStorage implements AEMultiTile, I
             }
         }
 
-        VoxelShape shape = VoxelShapes.empty();
-        for (final AxisAlignedBB bx : boxes) {
-            shape = VoxelShapes.or(shape, VoxelShapes.create(bx));
-        }
-        return shape;
+        return VoxelShapeCache.get(boxes);
     }
 
     private void invalidateShapes() {
diff --git a/src/main/java/appeng/parts/VoxelShapeCache.java b/src/main/java/appeng/parts/VoxelShapeCache.java
new file mode 100644
index 000000000..52b28f3ac
--- /dev/null
+++ b/src/main/java/appeng/parts/VoxelShapeCache.java
@@ -0,0 +1,81 @@
+/*
+ * This file is part of Applied Energistics 2.
+ * Copyright (c) 2013 - 2015, AlgorithmX2, All rights reserved.
+ *
+ * Applied Energistics 2 is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Applied Energistics 2 is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Applied Energistics 2.  If not, see <http://www.gnu.org/licenses/lgpl>.
+ */
+
+package appeng.parts;
+
+import java.util.List;
+
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+
+import net.minecraft.util.math.AxisAlignedBB;
+import net.minecraft.util.math.shapes.IBooleanFunction;
+import net.minecraft.util.math.shapes.VoxelShape;
+import net.minecraft.util.math.shapes.VoxelShapes;
+
+/**
+ * While creation of a {@link VoxelShape} with
+ * {@link VoxelShapes#create(AxisAlignedBB)} is fast enough, combining voxel
+ * shapes with {@link VoxelShapes#or(VoxelShape, VoxelShape)} or any other
+ * combination method, as well as {@link VoxelShape#simplify()} are <b>extremely
+ * slow</b>. For example: Creating a VoxelShape for a list of 5 bounding boxes
+ * 10,000 times takes about 1.7 seconds.
+ *
+ * <p>
+ * To reduce the impact of this on cables, we introduce a global voxel shape
+ * cache so that cables can share their combined voxel shapes better.
+ */
+final class VoxelShapeCache {
+
+    // Why using a List here should not make much of a difference vs. using a Set:
+    // The part's bounding box depends on the side it is attached to, and the sides
+    // are iterated over in a fixed order, meaning the order of bounding boxes
+    // should
+    // be the same for a same set of parts.
+    private static final LoadingCache<List<AxisAlignedBB>, VoxelShape> CACHE = CacheBuilder.newBuilder()//
+            .maximumSize(10000L)//
+            .build(new CacheLoader<List<AxisAlignedBB>, VoxelShape>() {
+                @Override
+                public VoxelShape load(List<AxisAlignedBB> key) {
+                    return create(key);
+                }
+            });
+
+    private VoxelShapeCache() {
+    }
+
+    public static VoxelShape get(List<AxisAlignedBB> boxes) {
+        return CACHE.getUnchecked(boxes);
+    }
+
+    private static VoxelShape create(List<AxisAlignedBB> boxes) {
+        if (boxes.isEmpty()) {
+            return VoxelShapes.empty();
+        }
+
+        int i = 0;
+        VoxelShape shape = VoxelShapes.create(boxes.get(i));
+        for (; i < boxes.size(); i++) {
+            AxisAlignedBB box = boxes.get(i);
+            shape = VoxelShapes.combine(shape, VoxelShapes.create(box), IBooleanFunction.OR);
+        }
+        return shape.simplify();
+    }
+
+}