Couple things, Part II

- Fixed a few major issues with dual cart assembly
- Attempted to fight the heavy loss of momentum in coupling physics

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/BlockMovementTraits.java

@@ -13,6 +13,7 @@ import com.simibubi.create.content.contraptions.components.structureMovement.bea
 import com.simibubi.create.content.contraptions.components.structureMovement.bearing.MechanicalBearingBlock;
 import com.simibubi.create.content.contraptions.components.structureMovement.bearing.MechanicalBearingTileEntity;
 import com.simibubi.create.content.contraptions.components.structureMovement.chassis.AbstractChassisBlock;
+import com.simibubi.create.content.contraptions.components.structureMovement.mounted.CartAssemblerBlock;
 import com.simibubi.create.content.contraptions.components.structureMovement.piston.MechanicalPistonBlock;
 import com.simibubi.create.content.contraptions.components.structureMovement.piston.MechanicalPistonBlock.PistonState;
 import com.simibubi.create.content.contraptions.components.structureMovement.pulley.PulleyBlock;
@@ -116,6 +117,8 @@ public class BlockMovementTraits {
 			return true;
 		if (block instanceof HorizontalFaceBlock)
 			return true;
+		if (block instanceof CartAssemblerBlock)
+			return false;
 		if (block instanceof AbstractRailBlock)
 			return true;
 		if (block instanceof RedstoneDiodeBlock)
@@ -197,6 +200,8 @@ public class BlockMovementTraits {
 	public static boolean notSupportive(BlockState state, Direction facing) {
 		if (AllBlocks.MECHANICAL_DRILL.has(state))
 			return state.get(BlockStateProperties.FACING) == facing;
+		if (AllBlocks.CART_ASSEMBLER.has(state))
+			return Direction.DOWN == facing;
 		if (AllBlocks.MECHANICAL_SAW.has(state))
 			return state.get(BlockStateProperties.FACING) == facing;
 		if (AllBlocks.PORTABLE_STORAGE_INTERFACE.has(state))

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/ContraptionEntity.java

@@ -6,8 +6,11 @@ import static com.simibubi.create.foundation.utility.AngleHelper.getShortestAngl
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map.Entry;
+import java.util.Optional;
 import java.util.UUID;
 
+import javax.annotation.Nullable;
+
 import org.apache.commons.lang3.tuple.MutablePair;
 
 import com.simibubi.create.AllEntityTypes;
@@ -72,7 +75,6 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 	protected Vec3d motionBeforeStall;
 	protected boolean stationary;
 	protected boolean initialized;
-	protected boolean onCoupling;
 	final List<Entity> collidingEntities = new ArrayList<>();
 	private boolean isSerializingFurnaceCart;
 
@@ -80,6 +82,11 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 	private static final DataParameter<Boolean> STALLED =
 		EntityDataManager.createKey(ContraptionEntity.class, DataSerializers.BOOLEAN);
 
+	private static final DataParameter<Optional<UUID>> COUPLING =
+		EntityDataManager.createKey(ContraptionEntity.class, DataSerializers.OPTIONAL_UNIQUE_ID);
+	private static final DataParameter<Optional<UUID>> COUPLED_CART =
+		EntityDataManager.createKey(ContraptionEntity.class, DataSerializers.OPTIONAL_UNIQUE_ID);
+
 	public float prevYaw;
 	public float prevPitch;
 	public float prevRoll;
@@ -109,11 +116,10 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 	}
 
 	public static ContraptionEntity createMounted(World world, Contraption contraption, float initialAngle,
-		Direction facing, boolean onCoupling) {
+		Direction facing) {
 		ContraptionEntity entity = createMounted(world, contraption, initialAngle);
 		entity.forcedAngle = facing.getHorizontalAngle();
 		entity.forceYaw(entity.forcedAngle);
-		entity.onCoupling = onCoupling;
 		return entity;
 	}
 
@@ -312,27 +318,36 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 	public void tickAsPassenger(Entity e) {
 		boolean rotationLock = false;
 		boolean pauseWhileRotating = false;
+		boolean rotating = false;
 
 		Entity riding = e;
 		while (riding.getRidingEntity() != null)
 			riding = riding.getRidingEntity();
 
+		boolean isOnCoupling = false;
 		if (contraption instanceof MountedContraption) {
 			MountedContraption mountedContraption = (MountedContraption) contraption;
-			if (onCoupling && riding instanceof AbstractMinecartEntity) {
+			UUID couplingId = getCouplingId();
-				MinecartCoupling coupling = MinecartCouplingHandler.getCoupling(world, riding.getUniqueID());
+			isOnCoupling = couplingId != null && riding instanceof AbstractMinecartEntity;
+			if (isOnCoupling) {
+				MinecartCoupling coupling = MinecartCouplingHandler.getCoupling(world, couplingId);
 				if (coupling != null && coupling.areBothEndsPresent()) {
+					boolean notOnMainCart = !coupling.getId()
+						.equals(riding.getUniqueID());
 					Vec3d positionVec = coupling.asCouple()
-						.getSecond()
+						.get(notOnMainCart)
 						.getPositionVec();
 					prevYaw = yaw;
 					prevPitch = pitch;
-					double diffZ = positionVec.z - getZ();
+					double diffZ = positionVec.z - riding.getZ();
-					double diffX = positionVec.x - getX();
+					double diffX = positionVec.x - riding.getX();
-					yaw = 90 + (float) (MathHelper.atan2(diffZ, diffX) * 180 / Math.PI);
+					yaw = (float) (MathHelper.atan2(diffZ, diffX) * 180 / Math.PI);
 					pitch = (float) (Math.atan2(positionVec.y - getY(), Math.sqrt(diffX * diffX + diffZ * diffZ)) * 180
 						/ Math.PI);
-					return;
+
+					if (notOnMainCart) {
+						yaw += 180;
+					}
 				}
 			}
 
@@ -341,10 +356,10 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 		}
 
 		Vec3d movementVector = riding.getMotion();
+		if (!isOnCoupling) {
 			if (riding instanceof BoatEntity)
 				movementVector = getPositionVec().subtract(prevPosX, prevPosY, prevPosZ);
 			Vec3d motion = movementVector.normalize();
-		boolean rotating = false;
 
 			if (!rotationLock) {
 				if (motion.length() > 0) {
@@ -362,6 +377,7 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 				else
 					rotating = true;
 			}
+		}
 
 		boolean wasStalled = isStalled();
 		if (!rotating || !pauseWhileRotating)
@@ -579,12 +595,13 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 	@Override
 	protected void registerData() {
 		this.dataManager.register(STALLED, false);
+		this.dataManager.register(COUPLING, null);
+		this.dataManager.register(COUPLED_CART, null);
 	}
 
 	@Override
 	protected void readAdditional(CompoundNBT compound) {
 		initialized = compound.getBoolean("Initialized");
-		onCoupling = compound.getBoolean("OnCoupling");
 		contraption = Contraption.fromNBT(world, compound.getCompound("Contraption"));
 		initialAngle = compound.getFloat("InitialAngle");
 		forceYaw(compound.contains("ForcedYaw") ? compound.getFloat("ForcedYaw") : initialAngle);
@@ -598,6 +615,14 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 		}
 		if (compound.contains("Controller"))
 			controllerPos = NBTUtil.readBlockPos(compound.getCompound("Controller"));
+		
+		if (compound.contains("OnCoupling")) {
+			setCouplingId(NBTUtil.readUniqueId(compound.getCompound("OnCoupling")));
+			setCoupledCart(NBTUtil.readUniqueId(compound.getCompound("CoupledCart")));
+		} else {
+			setCouplingId(null);
+			setCoupledCart(null);
+		}
 	}
 
 	public void forceYaw(float forcedYaw) {
@@ -636,7 +661,11 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 		compound.putFloat("InitialAngle", initialAngle);
 		compound.putBoolean("Stalled", isStalled());
 		compound.putBoolean("Initialized", initialized);
-		compound.putBoolean("OnCoupling", onCoupling);
+		
+		if (getCouplingId() != null) {
+			compound.put("OnCoupling", NBTUtil.writeUniqueId(getCouplingId()));
+			compound.put("CoupledCart", NBTUtil.writeUniqueId(getCoupledCart()));
+		}
 	}
 
 	@Override
@@ -849,4 +878,24 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 		return e.getPushReaction() == PushReaction.NORMAL;
 	}
 
+	@Nullable
+	public UUID getCouplingId() {
+		Optional<UUID> uuid = dataManager.get(COUPLING);
+		return uuid == null ? null : uuid.isPresent() ? uuid.get() : null;
+	}
+
+	public void setCouplingId(UUID id) {
+		dataManager.set(COUPLING, Optional.ofNullable(id));
+	}
+
+	@Nullable
+	public UUID getCoupledCart() {
+		Optional<UUID> uuid = dataManager.get(COUPLED_CART);
+		return uuid.isPresent() ? uuid.get() : null;
+	}
+
+	public void setCoupledCart(UUID id) {
+		dataManager.set(COUPLED_CART, Optional.ofNullable(id));
+	}
+
 }

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/CartAssemblerBlock.java

@@ -46,6 +46,7 @@ import net.minecraft.util.SoundCategory;
 import net.minecraft.util.SoundEvents;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.BlockRayTraceResult;
+import net.minecraft.util.math.MathHelper;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.util.math.shapes.ISelectionContext;
 import net.minecraft.util.math.shapes.VoxelShape;
@@ -212,12 +213,24 @@ public class CartAssemblerBlock extends AbstractRailBlock
 		float initialAngle = facing.getHorizontalAngle();
 
 		withTileEntityDo(world, pos, te -> contraption.rotationMode = CartMovementMode.values()[te.movementMode.value]);
+
 		boolean couplingFound = contraption.connectedCart != null;
-		if (couplingFound)
+		if (couplingFound) {
 			MinecartCouplingHandler.connectCarts(null, world, cart.getEntityId(),
 				contraption.connectedCart.getEntityId());
-		ContraptionEntity entity =
+			Vec3d diff = contraption.connectedCart.getPositionVec()
-			ContraptionEntity.createMounted(world, contraption, initialAngle, facing, couplingFound);
+				.subtract(cart.getPositionVec());
+			initialAngle = Direction.fromAngle(MathHelper.atan2(diff.z, diff.x) * 180 / Math.PI)
+				.getHorizontalAngle();
+		}
+
+		ContraptionEntity entity = ContraptionEntity.createMounted(world, contraption, initialAngle, facing);
+
+		if (couplingFound) {
+			entity.setCouplingId(cart.getUniqueID());
+			entity.setCoupledCart(contraption.connectedCart.getUniqueID());
+		}
+
 		entity.setPosition(pos.getX(), pos.getY(), pos.getZ());
 		world.addEntity(entity);
 		entity.startRiding(cart);

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/MinecartContraptionItem.java

@@ -159,8 +159,7 @@ public class MinecartContraptionItem extends Item {
 			ContraptionEntity contraption;
 
 			if (newFacing != null)
-				contraption =
+				contraption = ContraptionEntity.createMounted(world, mountedContraption, initialAngle, newFacing);
-					ContraptionEntity.createMounted(world, mountedContraption, initialAngle, newFacing, false);
 			else
 				contraption = ContraptionEntity.createMounted(world, mountedContraption, initialAngle);
 

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/MountedContraption.java

@@ -123,7 +123,7 @@ public class MountedContraption extends Contraption {
 
 	@Override
 	protected boolean customBlockRemoval(IWorld world, BlockPos pos, BlockState state) {
-		return pos.equals(anchor);
+		return AllBlocks.MINECART_ANCHOR.has(state);
 	}
 
 }

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/train/MinecartCouplingHandler.java

@@ -12,9 +12,11 @@ import javax.annotation.Nullable;
 import org.apache.commons.lang3.tuple.Pair;
 
 import com.mojang.blaze3d.matrix.MatrixStack;
+import com.simibubi.create.content.contraptions.components.structureMovement.ContraptionEntity;
 import com.simibubi.create.content.contraptions.components.structureMovement.train.MinecartCouplingSerializer.CouplingData;
 import com.simibubi.create.foundation.config.AllConfigs;
 import com.simibubi.create.foundation.networking.AllPackets;
+import com.simibubi.create.foundation.utility.Couple;
 import com.simibubi.create.foundation.utility.WorldAttached;
 
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
@@ -376,6 +378,25 @@ public class MinecartCouplingHandler {
 	public static void flipCoupling(World world, MinecartCoupling coupling) {
 		Map<UUID, MinecartCoupling> map = loadedCouplings.get(world);
 		map.remove(coupling.getId());
+
+		if (coupling.areBothEndsPresent()) {
+			Couple<AbstractMinecartEntity> carts = coupling.asCouple();
+			Couple<UUID> ids = carts.map(Entity::getUniqueID);
+			carts.map(c -> c.isBeingRidden() ? c.getPassengers()
+				.get(0) : null)
+				.map(c -> c instanceof ContraptionEntity ? (ContraptionEntity) c : null)
+				.forEachWithContext((contraption, current) -> {
+					if (contraption == null || contraption.getCouplingId() == null)
+						return;
+					boolean switchTo = contraption.getCouplingId()
+						.equals(ids.get(current)) ? !current : current;
+					if (!carts.get(switchTo).getUniqueID().equals(contraption.getCoupledCart()))
+						return;
+					contraption.setCouplingId(ids.get(switchTo));
+					contraption.setCoupledCart(ids.get(!switchTo));
+				});
+		}
+
 		coupling.flip();
 		map.put(coupling.getId(), coupling);
 	}

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/train/MinecartSim2020.java

@@ -13,9 +13,7 @@ import net.minecraft.block.AbstractRailBlock;
 import net.minecraft.block.BlockState;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.item.minecart.AbstractMinecartEntity;
-import net.minecraft.entity.item.minecart.ContainerMinecartEntity;
 import net.minecraft.entity.item.minecart.FurnaceMinecartEntity;
-import net.minecraft.inventory.container.Container;
 import net.minecraft.state.properties.RailShape;
 import net.minecraft.util.Direction;
 import net.minecraft.util.Util;
@@ -49,24 +47,24 @@ public class MinecartSim2020 {
 		});
 
 	public static Vec3d predictMotionOf(AbstractMinecartEntity cart) {
-
 		if (cart instanceof FurnaceMinecartEntity) {
 			return cart.getPositionVec()
 				.subtract(cart.lastTickPosX, cart.lastTickPosY, cart.lastTickPosZ);
 		}
-		if (cart instanceof ContainerMinecartEntity) {
+		return cart.getMotion().scale(1.03f);
-			ContainerMinecartEntity containerCart = (ContainerMinecartEntity) cart;
+//		if (cart instanceof ContainerMinecartEntity) {
-			float f = 0.98F;
+//			ContainerMinecartEntity containerCart = (ContainerMinecartEntity) cart;
-			if (containerCart.isEmpty())
+//			float f = 0.98F;
-				return cart.getMotion()
+//			if (containerCart.isEmpty())
-					.mul(f, 0.0D, f);
+//				return cart.getMotion()
-			int i = 15 - Container.calcRedstoneFromInventory(containerCart);
+//					.mul(f, 0.0D, f);
-			f += (float) i * 0.001F;
+//			int i = 15 - Container.calcRedstoneFromInventory(containerCart);
-			return cart.getMotion()
+//			f += (float) i * 0.001F;
-				.mul(f, 0.0D, f);
+//			return cart.getMotion()
-		}
+//				.mul(f, 0.0D, f);
-		return cart.getMotion()
+//		}
-			.scale(cart.isBeingRidden() ? 0.997D : 0.96D);
+//		return cart.getMotion()
+//			.scale(cart.isBeingRidden() ? 0.997D : 0.96D);
 	}
 
 	public static boolean canAddMotion(AbstractMinecartEntity c) {