Fix fall damage, ladders, hitbox calculations, clipping, camera offset, and unicorn's teleportation when in inverted gravity

src/main/java/com/minelittlepony/unicopia/ability/UnicornTeleportAbility.java

@@ -27,6 +27,7 @@ import net.minecraft.sound.SoundCategory;
 import net.minecraft.text.Text;
 import net.minecraft.util.Identifier;
 import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.math.Direction;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.util.shape.VoxelShape;
 import net.minecraft.world.World;
@@ -89,8 +90,10 @@ public class UnicornTeleportAbility implements Ability<Pos> {
         return trace.getBlockOrEntityPos().map(pos -> {
             final BlockPos originalPos = pos;
 
+            Direction globalUp = player.getPhysics().isGravityNegative() ? Direction.DOWN : Direction.UP;
+
             boolean originalPosHasSupport = exception(w, pos, player.asEntity());
-            boolean originalPosValid = enterable(w, pos.up()) && enterable(w, pos.up(2));
+            boolean originalPosValid = enterable(w, pos.offset(globalUp)) && enterable(w, pos.offset(globalUp, 2));
 
             if (w.getBlockState(pos).isOf(Blocks.POWDER_SNOW) && !PowderSnowBlock.canWalkOnPowderSnow(player.asEntity())) {
                 return null;
@@ -111,11 +114,11 @@ public class UnicornTeleportAbility implements Ability<Pos> {
             if (pos.getX() != originalPos.getX() || pos.getZ() != originalPos.getZ()) {
                 // check support
                 int steps = 0;
-                while (enterable(w, pos.down())) {
+                while (enterable(w, pos.offset(globalUp.getOpposite()))) {
-                    pos = pos.down();
+                    pos = pos.offset(globalUp.getOpposite());
                     if (++steps > 2) {
                         if (originalPosValid) {
-                            pos = originalPos.up();
+                            pos = originalPos.offset(globalUp);
                             break;
                         } else {
                             return null;
@@ -125,7 +128,7 @@ public class UnicornTeleportAbility implements Ability<Pos> {
             }
 
             if ((!enterable(w, pos) && exception(w, pos, player.asEntity()))
-             || (!enterable(w, pos.up()) && exception(w, pos.up(), player.asEntity()))) {
+             || (!enterable(w, pos.offset(globalUp)) && exception(w, pos.offset(globalUp), player.asEntity()))) {
                 return null;
             }
 

src/main/java/com/minelittlepony/unicopia/client/render/WorldRenderDelegate.java

@@ -175,44 +175,40 @@ public class WorldRenderDelegate {
 
         boolean negative = pony.getPhysics().isGravityNegative();
 
-        float roll = negative ? 180 : 0;
-
-        roll = pony instanceof Pony ? ((Pony)pony).getInterpolator().interpolate("g_roll", roll, 15) : roll;
-
         matrices.translate(x, y + owner.getHeight() / 2, z);
 
-        matrices.multiply(RotationAxis.POSITIVE_X.rotationDegrees(roll));
-        matrices.multiply(RotationAxis.POSITIVE_Y.rotationDegrees(roll));
-
         if (pony instanceof Pony p) {
-            roll = p.getCamera().calculateRoll();
+            float sidewaysRoll = p.getCamera().calculateRoll();
-            if (negative) {
-                roll -= 180;
-            }
 
             if (p.getAcrobatics().isFloppy()) {
                 matrices.translate(0, -0.5, 0);
                 p.asEntity().setBodyYaw(0);
                 p.asEntity().setYaw(0);
-                matrices.multiply(RotationAxis.NEGATIVE_X.rotationDegrees(90));
+                sidewaysRoll += 90;
             }
 
-            matrices.multiply(RotationAxis.NEGATIVE_Y.rotationDegrees(yaw));
+            matrices.multiply(RotationAxis.POSITIVE_Y.rotationDegrees(90));
-            matrices.multiply(RotationAxis.POSITIVE_Z.rotationDegrees(roll));
+            matrices.multiply(RotationAxis.POSITIVE_X.rotationDegrees(sidewaysRoll));
+            matrices.multiply(RotationAxis.POSITIVE_Y.rotationDegrees(-90));
 
-            float diveAngle = p.getInterpolator().interpolate("g_kdive", p.getMotion().isDiving() ? 80 : 0, 15);
+            float forwardPitch = p.getInterpolator().interpolate("g_kdive", p.getMotion().isDiving() ? 80 : 0, 15);
 
-            matrices.multiply(RotationAxis.POSITIVE_X.rotationDegrees(diveAngle));
+            matrices.multiply(RotationAxis.POSITIVE_X.rotationDegrees(forwardPitch));
-            matrices.multiply(RotationAxis.POSITIVE_Y.rotationDegrees(yaw));
 
             if (p.getCompositeRace().includes(Race.SEAPONY)
                     && pony.asEntity().isSubmergedInWater()
                     && MineLPDelegate.getInstance().getPlayerPonyRace(p.asEntity()) != Race.SEAPONY) {
                 ModelPartHooks.startCollecting();
             }
-        } else if (pony instanceof Creature creature && smittenEyesRenderer.isSmitten(creature)) {
+        } else {
+            float roll = negative ? 180 : 0;
+
+            matrices.multiply(RotationAxis.POSITIVE_Z.rotationDegrees(roll));
+
+            if (pony instanceof Creature creature && smittenEyesRenderer.isSmitten(creature)) {
                 ModelPartHooks.startCollecting();
             }
+        }
 
         matrices.translate(-x, -y - owner.getHeight() / 2, -z);
 
@@ -224,7 +220,7 @@ public class WorldRenderDelegate {
     }
 
     private void flipAngles(Entity entity) {
-        if (entity instanceof PlayerEntity) {
+        if (entity instanceof PlayerEntity player) {
             entity.prevYaw *= -1;
             entity.setYaw(entity.getYaw() * -1);
 

src/main/java/com/minelittlepony/unicopia/command/GravityCommand.java

@@ -1,15 +1,15 @@
 package com.minelittlepony.unicopia.command;
 
-import java.util.Arrays;
+import java.util.Collection;
-import java.util.stream.Stream;
+import java.util.List;
-
+import java.util.Objects;
-import com.google.common.collect.Streams;
+import com.minelittlepony.unicopia.entity.Living;
-import com.minelittlepony.unicopia.entity.player.Pony;
 import com.mojang.brigadier.arguments.FloatArgumentType;
 import com.mojang.brigadier.builder.LiteralArgumentBuilder;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 
 import net.minecraft.command.argument.EntityArgumentType;
+import net.minecraft.entity.Entity;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.server.command.CommandManager;
 import net.minecraft.server.command.ServerCommandSource;
@@ -22,45 +22,48 @@ class GravityCommand {
         return CommandManager.literal("gravity").requires(s -> s.hasPermissionLevel(2))
             .then(CommandManager.literal("get")
                             .executes(context -> get(context.getSource(), context.getSource().getPlayer(), true))
-                   .then(CommandManager.argument("target", EntityArgumentType.player())
+                   .then(CommandManager.argument("target", EntityArgumentType.entity())
-                            .executes(context -> get(context.getSource(), EntityArgumentType.getPlayer(context, "target"), false))
+                            .executes(context -> get(context.getSource(), EntityArgumentType.getEntity(context, "target"), false))
                     ))
             .then(CommandManager.literal("set")
                    .then(CommandManager.argument("gravity", FloatArgumentType.floatArg(-99, 99))
-                               .executes(context -> set(context.getSource(), context.getSource().getPlayer(), FloatArgumentType.getFloat(context, "gravity"), true))
+                               .executes(context -> set(context.getSource(), List.of(context.getSource().getPlayer()), FloatArgumentType.getFloat(context, "gravity"), true))
-                   .then(CommandManager.argument("target", EntityArgumentType.player())
+                   .then(CommandManager.argument("target", EntityArgumentType.entities())
-                               .executes(context -> set(context.getSource(), EntityArgumentType.getPlayer(context, "target"), FloatArgumentType.getFloat(context, "gravity"), false))
+                               .executes(context -> set(context.getSource(), EntityArgumentType.getEntities(context, "target"), FloatArgumentType.getFloat(context, "gravity"), false))
                    )));
     }
 
-    static int get(ServerCommandSource source, PlayerEntity player, boolean isSelf) throws CommandSyntaxException {
+    static int get(ServerCommandSource source, Entity target, boolean isSelf) throws CommandSyntaxException {
-        sendFeedback(source, player, "get", false, Pony.of(player).getPhysics().getGravityModifier());
+        Living<?> l = Living.living(target);
-        return 0;
-    }
 
-    static int set(ServerCommandSource source, PlayerEntity player, float gravity, boolean isSelf) {
+        float gravity = l == null ? 1 : l.getPhysics().getGravityModifier();
-
+        if (source.getEntity() == target) {
-        Pony iplayer = Pony.of(player);
+            source.sendFeedback(() -> Text.translatable("commands.gravity.get.self", gravity), true);
-
-        iplayer.getPhysics().setBaseGravityModifier(gravity);
-        iplayer.setDirty();
-
-        sendFeedback(source, player, "set", true, gravity);
-        return 0;
-    }
-
-
-    static void sendFeedback(ServerCommandSource source, PlayerEntity player, String key, boolean notifyTarget, Object...arguments) {
-        String translationKey = "commands.gravity." + key;
-
-        if (source.getEntity() == player) {
-            source.sendFeedback(() -> Text.translatable(translationKey + ".self", arguments), true);
         } else {
-            if (notifyTarget && source.getWorld().getGameRules().getBoolean(GameRules.SEND_COMMAND_FEEDBACK)) {
+            source.sendFeedback(() -> Text.translatable("commands.gravity.get.other", target.getDisplayName(), gravity), true);
-                player.sendMessage(Text.translatable(translationKey, arguments));
+        }
+        return 0;
     }
 
-            source.sendFeedback(() -> Text.translatable(translationKey + ".other", Streams.concat(Stream.of(player.getDisplayName()), Arrays.stream(arguments)).toArray()), true);
+    static int set(ServerCommandSource source, Collection<? extends Entity> targets, float gravity, boolean isSelf) {
+        List<Entity> affected = targets.stream().map(Living::living).filter(Objects::nonNull).map(l -> {
+            l.getPhysics().setBaseGravityModifier(gravity);
+            l.setDirty();
+            if (l.asEntity() instanceof PlayerEntity player) {
+                if (source.getEntity() == player) {
+                    player.sendMessage(Text.translatable("commands.gravity.set.self", gravity));
+                } else if (source.getWorld().getGameRules().getBoolean(GameRules.SEND_COMMAND_FEEDBACK)) {
+                    player.sendMessage(Text.translatable("commands.gravity.set.other", l.asEntity().getDisplayName(), gravity));
                 }
             }
+            return (Entity)l.asEntity();
+        }).toList();
+
+        if (affected.size() == 1) {
+            source.sendFeedback(() -> Text.translatable("commands.gravity.set.other", affected.get(0).getDisplayName()), true);
+        } else {
+            source.sendFeedback(() -> Text.translatable("commands.gravity.set.multiple", affected.size()), true);
+        }
+        return 0;
+    }
 }

src/main/java/com/minelittlepony/unicopia/entity/EntityPhysics.java

@@ -4,18 +4,13 @@ import com.minelittlepony.unicopia.entity.mob.UEntityAttributes;
 import com.minelittlepony.unicopia.util.Copyable;
 import com.minelittlepony.unicopia.util.Tickable;
 
-import net.minecraft.block.BlockRenderType;
 import net.minecraft.block.BlockState;
 import net.minecraft.block.FenceGateBlock;
 import net.minecraft.entity.Entity;
-import net.minecraft.entity.EntityPose;
 import net.minecraft.entity.LivingEntity;
-import net.minecraft.entity.MovementType;
 import net.minecraft.entity.data.TrackedData;
 import net.minecraft.entity.mob.MobEntity;
 import net.minecraft.nbt.NbtCompound;
-import net.minecraft.particle.BlockStateParticleEffect;
-import net.minecraft.particle.ParticleTypes;
 import net.minecraft.registry.tag.BlockTags;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.MathHelper;
@@ -37,22 +32,12 @@ public class EntityPhysics<T extends Entity> implements Physics, Copyable<Entity
     @Override
     public void tick() {
         if (isGravityNegative()) {
-            if (isGravityNegative() && !entity.isSneaking() && entity.isInSneakingPose()) {
-                float currentHeight = entity.getDimensions(entity.getPose()).height;
-                float sneakingHeight = entity.getDimensions(EntityPose.STANDING).height;
-
-                entity.move(MovementType.SELF, new Vec3d(0, -(currentHeight - sneakingHeight), 0));
-                entity.setPose(EntityPose.STANDING);
-            }
-
             if (entity.getY() > entity.getWorld().getHeight() + 64) {
                 entity.damage(entity.getDamageSources().outOfWorld(), 4.0F);
             }
-
-            entity.setOnGround(entity.verticalCollision && entity.getVelocity().getY() > 0);
         }
 
-        float gravity = this.getGravityModifier();
+        float gravity = getGravityModifier();
         if (gravity != lastGravity) {
             lastGravity = gravity;
 
@@ -87,8 +72,6 @@ public class EntityPhysics<T extends Entity> implements Physics, Copyable<Entity
     @Override
     public BlockPos getHeadPosition() {
 
-        entity.setOnGround(false);
-
         BlockPos pos = new BlockPos(
                 MathHelper.floor(entity.getX()),
                 MathHelper.floor(entity.getY() + entity.getHeight() + 0.20000000298023224D),
@@ -99,29 +82,13 @@ public class EntityPhysics<T extends Entity> implements Physics, Copyable<Entity
             BlockPos below = pos.down();
             BlockState block = entity.getWorld().getBlockState(below);
             if (block.isIn(BlockTags.FENCES) || block.isIn(BlockTags.WALLS) || block.getBlock() instanceof FenceGateBlock) {
-                entity.setOnGround(true);
                 return below;
             }
-        } else {
-            entity.setOnGround(true);
         }
 
         return pos;
     }
 
-    @Override
-    public void spawnSprintingParticles() {
-        BlockState state = entity.getWorld().getBlockState(getHeadPosition());
-        if (state.getRenderType() != BlockRenderType.INVISIBLE) {
-            Vec3d vel = entity.getVelocity();
-            entity.getWorld().addParticle(new BlockStateParticleEffect(ParticleTypes.BLOCK, state),
-                    entity.getX() + (entity.getWorld().random.nextFloat() - 0.5D) * entity.getWidth(),
-                    entity.getY() + entity.getHeight() - 0.1D,
-                    entity.getZ() + (entity.getWorld().random.nextFloat() - 0.5D) * entity.getWidth(),
-                    vel.x * -4, -1.5D, vel.z * -4);
-        }
-    }
-
     @Override
     public void setBaseGravityModifier(float constant) {
         entity.getDataTracker().set(gravity, constant);

src/main/java/com/minelittlepony/unicopia/entity/Living.java

@@ -476,12 +476,6 @@ public abstract class Living<T extends LivingEntity> implements Equine<T>, Caste
         return false;
     }
 
-    public void onJump() {
-        if (getPhysics().isGravityNegative()) {
-            entity.setVelocity(entity.getVelocity().multiply(1, -1, 1));
-        }
-    }
-
     @Nullable
     public final Caster<?> getAttacker() {
         return attacker;

src/main/java/com/minelittlepony/unicopia/entity/Physics.java

@@ -21,8 +21,6 @@ public interface Physics extends NbtSerialisable {
 
     BlockPos getHeadPosition();
 
-    void spawnSprintingParticles();
-
     default boolean isGravityNegative() {
         return getGravityModifier() < 0;
     }

src/main/java/com/minelittlepony/unicopia/entity/player/PlayerDimensions.java

@@ -25,11 +25,7 @@ public final class PlayerDimensions {
                 .or(() -> physics.isFlyingSurvival ? FLYING_EYE_HEIGHT : physics.isGravityNegative() ? Optional.of(dimensions.height) : Optional.empty())
                 .map(h -> {
                     if (physics.isGravityNegative()) {
-                        if (pony.asEntity().isSneaking()) {
+                        return dimensions.height - h + 0.1F;
-                            h += 0.2F;
-                        }
-
-                        return dimensions.height - h;
                     }
                     return h;
                 });

src/main/java/com/minelittlepony/unicopia/entity/player/PlayerPhysics.java

@@ -301,10 +301,6 @@ public class PlayerPhysics extends EntityPhysics<PlayerEntity> implements Tickab
             if (entity.isOnGround() || (!creative && entity.horizontalCollision)) {
                 cancelFlight(false);
             }
-
-            if (entity.isClimbing() && (entity.horizontalCollision || ((LivingEntityDuck)entity).isJumping())) {
-                velocity.y = -0.2F;
-            }
         }
 
         isFlyingSurvival = entity.getAbilities().flying && !creative;

src/main/java/com/minelittlepony/unicopia/entity/player/Pony.java

@@ -631,7 +631,7 @@ public class Pony extends Living<PlayerEntity> implements Copyable<Pony>, Update
             float max = 0.6F;
             return Optional.of(new Vec3d(
                     MathHelper.clamp(speed.x * factor, -max, max),
-                    speed.y * ((speed.y * getPhysics().getGravitySignum()) > 0 ? 1.2 : 1.101),
+                    speed.y * (speed.y > 0 ? 1.2 : 1.101),
                     MathHelper.clamp(speed.z * factor, -max, max)
             ));
         }
@@ -715,11 +715,8 @@ public class Pony extends Living<PlayerEntity> implements Copyable<Pony>, Update
     }
 
     public Optional<Float> onImpact(float distance, float damageMultiplier, DamageSource cause) {
-
         float originalDistance = distance;
 
-        distance *= gravity.getGravityModifier();
-
         boolean extraProtection = getSpellSlot().get(SpellType.SHIELD, false).isPresent();
 
         if (!entity.isCreative() && !entity.isSpectator()) {

src/main/java/com/minelittlepony/unicopia/mixin/MixinLivingEntity.java

@@ -128,11 +128,6 @@ abstract class MixinLivingEntity extends Entity implements LivingEntityDuck, Equ
         get().adjustMovementSpeedInWater(info.getReturnValue()).ifPresent(info::setReturnValue);
     }
 
-    @Inject(method = "jump()V", at = @At("RETURN"))
-    private void onJump(CallbackInfo info) {
-        get().onJump();
-    }
-
     @Inject(method = "tick()V", at = @At("HEAD"), cancellable = true)
     private void beforeTick(CallbackInfo info) {
         if (get().beforeUpdate()) {
@@ -186,21 +181,4 @@ abstract class MixinLivingEntity extends Entity implements LivingEntityDuck, Equ
             setLivingFlag(2, hand == Hand.OFF_HAND);
         }
     }
-
-    @Override
-    public BlockPos getBlockPos() {
-        if (get().getPhysics().isGravityNegative()) {
-            return get().getPhysics().getHeadPosition();
-        }
-        return super.getBlockPos();
-    }
-
-    @Override
-    protected void spawnSprintingParticles() {
-        if (get().getPhysics().isGravityNegative()) {
-            get().getPhysics().spawnSprintingParticles();
-        } else {
-            super.spawnSprintingParticles();
-        }
-    }
 }

src/main/java/com/minelittlepony/unicopia/mixin/client/MixinKeyboardInput.java

@@ -27,12 +27,6 @@ abstract class MixinKeyboardInput extends Input {
                 pressingRight = tmp;
 
                 movementSideways = -movementSideways;
-
-                /*if (player.asEntity().getAbilities().flying && !player.getPhysics().isFlying()) {
-                    tmp = jumping;
-                    jumping = sneaking;
-                    sneaking = tmp;
-                }*/
             }
 
             if (EffectUtils.getAmplifier(MinecraftClient.getInstance().player, UEffects.PARALYSIS) > 1) {

src/main/java/com/minelittlepony/unicopia/mixin/gravity/MixinEntity.java

@@ -5,6 +5,7 @@ import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.At.Shift;
 import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
 import org.spongepowered.asm.mixin.injection.ModifyVariable;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
@@ -12,7 +13,9 @@ import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 import com.minelittlepony.unicopia.entity.Equine;
 
 import net.minecraft.entity.Entity;
+import net.minecraft.entity.EntityPose;
 import net.minecraft.entity.MovementType;
+import net.minecraft.util.math.Box;
 import net.minecraft.util.math.Vec3d;
 
 @Mixin(value = Entity.class, priority = 29000)
@@ -21,7 +24,7 @@ abstract class MixinEntity {
     // we invert y when moving
     @ModifyVariable(method = "move", at = @At("HEAD"), argsOnly = true)
     private Vec3d modifyMovement(Vec3d movement) {
-        if (this instanceof Equine.Container eq && eq.get().getPhysics().isGravityNegative()) {
+        if (unicopiaIsGravityInverted()) {
             return movement.multiply(1, -1, 1);
         }
         return movement;
@@ -35,14 +38,6 @@ abstract class MixinEntity {
         }
     }
 
-    // invert jumping velocity so we can jump
-    @Inject(method = "getJumpVelocityMultiplier", at = @At("RETURN"), cancellable = true)
-    private void onGetJumpVelocityMultiplier(CallbackInfoReturnable<Float> info) {
-        if (this instanceof Equine.Container eq && eq.get().getPhysics().isGravityNegative()) {
-            info.setReturnValue(-info.getReturnValue());
-        }
-    }
-
     // invert offsets so it can properly find the block we're walking on
     @ModifyVariable(method = "getPosWithYOffset", at = @At("HEAD"), argsOnly = true)
     private float onGetPosWithYOffset(float offset) {
@@ -53,12 +48,27 @@ abstract class MixinEntity {
     }
 
     // fix sprinting particles
-    @Inject(method = "spawnSprintingParticles", at = @At("HEAD"), cancellable = true)
+    @ModifyArg(method = "spawnSprintingParticles",
-    protected void spawnSprintingParticles(CallbackInfo info) {
+            at = @At(value = "INVOKE",
+                target = "net/minecraft/world/World.addParticle(Lnet/minecraft/particle/ParticleEffect;DDDDDD)V"),
+            index = 2)
+    private double modifyParticleY(double y) {
         if (this instanceof Equine.Container eq && eq.get().getPhysics().isGravityNegative()) {
-            eq.get().getPhysics().spawnSprintingParticles();
+            Entity self = eq.get().asEntity();
-            info.cancel();
+            return self.getHeight() - y + (self.getY() * 2);
         }
+        return y;
+    }
+
+    // fix fall damage
+    @ModifyArg(
+            method = "move",
+            at = @At(value = "INVOKE", target = "net/minecraft/entity/Entity.fall(DZLnet/minecraft/block/BlockState;Lnet/minecraft/util/math/BlockPos;)V"))
+    private double modifyFallDistance(double heightDifference) {
+        if (unicopiaIsGravityInverted()) {
+            return -heightDifference;
+        }
+        return heightDifference;
     }
 
     // invert check for walking up a step
@@ -68,9 +78,43 @@ abstract class MixinEntity {
             argsOnly = true)
 
     private static Vec3d modifyMovementForStepheight(Vec3d movement, @Nullable Entity entity) {
-        if (entity != null && movement.getY() == entity.getStepHeight()) {
+        if (entity instanceof Equine.Container eq && eq.get().getPhysics().isGravityNegative() && movement.getY() == entity.getStepHeight()) {
             return movement.multiply(1, -1, 1);
         }
         return movement;
     }
+
+    @Inject(method = {"calculateBoundsForPose"}, at = @At("RETURN"), cancellable = true)
+    private void adjustPoseBoxForGravity(EntityPose pos, CallbackInfoReturnable<Box> info) {
+        unicopiaReAnchorBoundingBox(info);
+    }
+
+    @Inject(method = {"calculateBoundingBox"}, at = @At("RETURN"), cancellable = true)
+    private void adjustPoseBoxForGravity(CallbackInfoReturnable<Box> info) {
+        if (unicopiaReAnchorBoundingBox(info)) {
+            Entity self = (Entity)(Object)this;
+            self.setPos(self.getX(), info.getReturnValue().minY, self.getZ());
+        }
+    }
+
+    private boolean unicopiaReAnchorBoundingBox(CallbackInfoReturnable<Box> info) {
+        if (this instanceof Equine.Container eq && eq.get().getPhysics().isGravityNegative()) {
+            Entity self = eq.get().asEntity();
+            Box box = info.getReturnValue();
+            Box oldBox = self.getBoundingBox();
+            double newHeight = box.getYLength();
+            if (newHeight > oldBox.getYLength()) {
+                double targetMaxY = oldBox.maxY;
+                Vec3d min = new Vec3d(box.minX, targetMaxY - newHeight, box.minZ);
+                Vec3d max = new Vec3d(box.maxX, targetMaxY, box.maxZ);
+                info.setReturnValue(new Box(min, max));
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean unicopiaIsGravityInverted() {
+        return this instanceof Equine.Container eq && eq.get().getPhysics().isGravityNegative();
+    }
 }

src/main/java/com/minelittlepony/unicopia/mixin/gravity/MixinLivingEntity.java

@@ -1,11 +1,15 @@
 package com.minelittlepony.unicopia.mixin.gravity;
 
 import org.spongepowered.asm.mixin.*;
+import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Constant;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
 import org.spongepowered.asm.mixin.injection.ModifyConstant;
 import com.minelittlepony.unicopia.entity.*;
+
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.LivingEntity;
+import net.minecraft.util.math.BlockPos;
 
 @Mixin(LivingEntity.class)
 abstract class MixinLivingEntity extends Entity implements Equine.Container<Living<?>> {
@@ -19,4 +23,23 @@ abstract class MixinLivingEntity extends Entity implements Equine.Container<Livi
     private double modifyGravity(double initial) {
         return Math.abs(get().getPhysics().calcGravity(initial));
     }
+
+    @ModifyArg(method = "fall",
+            at = @At(value = "INVOKE",
+                target = "net/minecraft/server/world/ServerWorld.spawnParticles(Lnet/minecraft/particle/ParticleEffect;DDDIDDDD)I"),
+            index = 2)
+    private double modifyParticleY(double y) {
+        if (get().getPhysics().isGravityNegative()) {
+            return y + getHeight();
+        }
+        return y;
+    }
+
+    @Override
+    public BlockPos getBlockPos() {
+        if (get().getPhysics().isGravityNegative()) {
+            return get().getPhysics().getHeadPosition();
+        }
+        return super.getBlockPos();
+    }
 }

src/main/java/com/minelittlepony/unicopia/mixin/gravity/MixinServerPlayNetworkHandler.java

@@ -0,0 +1,29 @@
+package com.minelittlepony.unicopia.mixin.gravity;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyVariable;
+import com.minelittlepony.unicopia.entity.player.Pony;
+
+import net.minecraft.network.listener.ServerPlayPacketListener;
+import net.minecraft.network.listener.TickablePacketListener;
+import net.minecraft.server.network.ServerPlayNetworkHandler;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.server.world.EntityTrackingListener;
+
+@Mixin(ServerPlayNetworkHandler.class)
+abstract class MixinServerPlayNetworkHandler
+implements EntityTrackingListener,
+TickablePacketListener,
+ServerPlayPacketListener {
+    @Shadow public ServerPlayerEntity player;
+
+    @ModifyVariable(method = "onPlayerMove", at = @At("STORE"), ordinal = 0)
+    private boolean flipLandingFlag(boolean value) {
+        if (Pony.of(this.player).getPhysics().isGravityNegative()) {
+            return !value;
+        }
+        return value;
+    }
+}

src/main/java/com/minelittlepony/unicopia/mixin/gravity/MixinServerPlayerEntity.java

@@ -0,0 +1,24 @@
+package com.minelittlepony.unicopia.mixin.gravity;
+
+import org.spongepowered.asm.mixin.*;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyVariable;
+
+import com.minelittlepony.unicopia.entity.Equine;
+
+import net.minecraft.server.network.ServerPlayerEntity;
+
+@Mixin(ServerPlayerEntity.class)
+abstract class MixinServerPlayerEntity {
+    @ModifyVariable(
+            method = "handleFall(DDDZ)V",
+            at = @At("HEAD"),
+            ordinal = 1,
+            argsOnly = true)
+    private double modifyFallDistance(double value) {
+        if (this instanceof Equine.Container eq && eq.get().getPhysics().isGravityNegative()) {
+            return -value;
+        }
+        return value;
+    }
+}

src/main/resources/assets/unicopia/lang/en_us.json

@@ -1383,6 +1383,7 @@
   "commands.gravity.set": "Your gravity has been updated to %f",
   "commands.gravity.set.self": "Set own gravity to %f",
   "commands.gravity.set.other": "Set %s's gravity to %f",
+  "commands.gravity.set.multiple": "Updated %s entities",
 
   "unicopia.options.title": "Unicopia Options",
   "unicopia.options.ignore_mine_lp": "Ignore Mine Little Pony",

src/main/resources/unicopia.mixin.json

@@ -59,6 +59,8 @@
     "gravity.MixinMobEntity",
     "gravity.MixinWorld",
     "gravity.MixinServerWorld",
+    "gravity.MixinServerPlayerEntity",
+    "gravity.MixinServerPlayNetworkHandler",
     "gravity.MixinWorldChunk",
     "trinkets.MixinTrinketSurvivalSlot",
     "trinkets.MixinTrinketItem",