feature: Interpolate target vehicle head movements (#8)

* Interpolate armour stand head movement when enabled * Remove unneeded field from mixin * Remove unneeded null checks Intellij was just running old code and gaslighting me about it * Update demo video in readme
lucyydotp · Jun 7, 2024 · eb1344f · eb1344f
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diff --git a/README.md b/README.md
@@ -3,7 +3,7 @@
 Passenger Perspective (or PaPers for short) is a Fabric mod that improves the camera for theme park servers.
 
 ### Demo video (click to watch)
-[![demo video](https://img.youtube.com/vi/4Bu7smcJ1GI/0.jpg)](https://youtu.be/4Bu7smcJ1GI)
+[![demo video](https://img.youtube.com/vi/TC_92oMWGjE/0.jpg)](https://youtu.be/https://youtu.be/TC_92oMWGjE)
 
 # How to use
 

diff --git a/src/main/java/me/lucyydotp/papers/ArmorStandExt.java b/src/main/java/me/lucyydotp/papers/ArmorStandExt.java
@@ -3,5 +3,18 @@
 import net.minecraft.core.Rotations;
 
 public interface ArmorStandExt {
-    Rotations paper$lastHeadRot();
+    /**
+     * Gets the armour stand's head rotation from the previous tick.
+     */
+    Rotations papers$lastHeadRot();
+
+    /**
+     * Gets whether this armour stand should interpolate movement for its head pose.
+     */
+    boolean papers$shouldInterpolateHead();
+
+    /**
+     * Sets whether this armour stand should interpolate movement for its head pose.
+     */
+    void papers$shouldInterpolateHead(boolean value);
 }
diff --git a/src/main/java/me/lucyydotp/papers/CameraPerspectiveMode.java b/src/main/java/me/lucyydotp/papers/CameraPerspectiveMode.java
@@ -37,6 +37,7 @@ final class ArmorStandHead implements CameraPerspectiveMode {
 
         public ArmorStandHead(ArmorStand armorStand) {
             this.armorStand = armorStand;
+            ((ArmorStandExt) armorStand).papers$shouldInterpolateHead(true);
             this.creationTime = armorStand.level.getGameTime();
             this.lastYRot = armorStand.yHeadRot;
         }
@@ -63,7 +64,7 @@ public void transform(PoseStack cameraPoseStack, float tickProgress, long time)
             lastYRot = lerpedYRot;
 
             final var pose = armorStand.getHeadPose();
-            final var lastPose = ((ArmorStandExt) armorStand).paper$lastHeadRot();
+            final var lastPose = ((ArmorStandExt) armorStand).papers$lastHeadRot();
             final var forward = Vec3.directionFromRotation(0, lerpedYRot).toVector3f();
 
             // fixme: properly slerp instead of doing whatever this is

diff --git a/src/main/java/me/lucyydotp/papers/mixin/ArmorStandArmorModelMixin.java b/src/main/java/me/lucyydotp/papers/mixin/ArmorStandArmorModelMixin.java
@@ -0,0 +1,53 @@
+package me.lucyydotp.papers.mixin;
+
+import me.lucyydotp.papers.ArmorStandExt;
+import net.minecraft.client.model.ArmorStandArmorModel;
+import net.minecraft.client.model.HumanoidModel;
+import net.minecraft.client.model.geom.ModelPart;
+import net.minecraft.util.Mth;
+import net.minecraft.world.entity.decoration.ArmorStand;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(ArmorStandArmorModel.class)
+public abstract class ArmorStandArmorModelMixin extends HumanoidModel<ArmorStand> {
+
+    public ArmorStandArmorModelMixin(ModelPart modelPart) {
+        super(modelPart);
+    }
+
+    @Inject(
+            method = "setupAnim(Lnet/minecraft/world/entity/decoration/ArmorStand;FFFFF)V",
+            at = @At(
+                    value = "INVOKE",
+                    target = "Lnet/minecraft/client/model/geom/ModelPart;copyFrom(Lnet/minecraft/client/model/geom/ModelPart;)V"
+            )
+    )
+    public void interpolateHeadIfNeeded(ArmorStand armorStand, float f, float g, float h, float i, float j, CallbackInfo ci) {
+        if (((ArmorStandExt) armorStand).papers$shouldInterpolateHead()) {
+            final var partialTickTime = h - (int) h;
+
+            final var lastPose = ((ArmorStandExt) armorStand).papers$lastHeadRot();
+
+            this.head.xRot = (float) Math.toRadians(Mth.rotLerp(
+                    partialTickTime,
+                    lastPose.getX(),
+                    armorStand.getHeadPose().getX()
+            ));
+
+            this.head.yRot = (float) Math.toRadians(Mth.rotLerp(
+                    partialTickTime,
+                    lastPose.getY(),
+                    armorStand.getHeadPose().getY()
+            ));
+
+            this.head.zRot = (float) Math.toRadians(Mth.rotLerp(
+                    partialTickTime,
+                    lastPose.getZ(),
+                    armorStand.getHeadPose().getZ()
+            ));
+        }
+    }
+}
diff --git a/src/main/java/me/lucyydotp/papers/mixin/ArmorStandMixin.java b/src/main/java/me/lucyydotp/papers/mixin/ArmorStandMixin.java
@@ -1,12 +1,12 @@
 package me.lucyydotp.papers.mixin;
 
-import com.llamalad7.mixinextras.sugar.Local;
 import me.lucyydotp.papers.ArmorStandExt;
 import me.lucyydotp.papers.CameraPerspectiveMode;
 import me.lucyydotp.papers.PassengerPerspectiveMod;
 import net.minecraft.core.Rotations;
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.entity.LivingEntity;
 import net.minecraft.world.entity.decoration.ArmorStand;
 import net.minecraft.world.level.Level;
 import org.spongepowered.asm.mixin.*;
@@ -15,7 +15,7 @@
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 
 @Mixin(ArmorStand.class)
-public abstract class ArmorStandMixin extends Entity implements ArmorStandExt {
+public abstract class ArmorStandMixin extends LivingEntity implements ArmorStandExt {
 
     @Shadow
     @Final
@@ -24,10 +24,14 @@ public abstract class ArmorStandMixin extends Entity implements ArmorStandExt {
     @Shadow
     private Rotations headPose;
 
+    @SuppressWarnings("UnusedAssignment")
     @Unique
     private Rotations papers$lastHeadRot = DEFAULT_HEAD_POSE;
 
-    public ArmorStandMixin(EntityType<?> entityType, Level level) {
+    @Unique
+    private boolean papers$shouldInterpolateHead;
+
+    public ArmorStandMixin(EntityType<? extends LivingEntity> entityType, Level level) {
         super(entityType, level);
         throw new AbstractMethodError("Mixin abstract class constructor");
     }
@@ -37,7 +41,9 @@ public ArmorStandMixin(EntityType<?> entityType, Level level) {
             at = @At("HEAD")
     )
     public void clearLastHeadPose(CallbackInfo ci) {
-        papers$lastHeadRot = headPose;
+        if (headPose != null) {
+            papers$lastHeadRot = headPose;
+        }
     }
 
     /**
@@ -55,7 +61,17 @@ public boolean isCurrentlyGlowing() {
     }
 
     @Override
-    public Rotations paper$lastHeadRot() {
+    public Rotations papers$lastHeadRot() {
         return papers$lastHeadRot;
     }
+
+    @Override
+    public boolean papers$shouldInterpolateHead() {
+        return papers$shouldInterpolateHead;
+    }
+
+    @Override
+    public void papers$shouldInterpolateHead(boolean value) {
+        papers$shouldInterpolateHead = value;
+    }
 }
diff --git a/src/main/resources/passenger-perspective.mixins.json b/src/main/resources/passenger-perspective.mixins.json
@@ -2,8 +2,8 @@
     "required": true,
     "package": "me.lucyydotp.papers.mixin",
     "client": [
-        "GameRendererMixin",
-        "ArmorStandMixin"
-
+        "ArmorStandArmorModelMixin",
+        "ArmorStandMixin",
+        "GameRendererMixin"
     ]
 }