[libgdx] Physics WIP.

spine-libgdx/spine-libgdx/src/com/esotericsoftware/spine/PhysicsConstraint.java

@@ -29,6 +29,7 @@
 
 package com.esotericsoftware.spine;
 
+import com.badlogic.gdx.math.Vector2;
 import com.badlogic.gdx.utils.Array;
 
 import com.esotericsoftware.spine.PhysicsConstraintData.Node;
@@ -47,10 +48,15 @@ public class PhysicsConstraint implements Updatable {
 
 	boolean active;
 
+	private final Skeleton skeleton;
+	float remaining, lastTime;
+	final Vector2 temp = new Vector2();
+
 	public PhysicsConstraint (PhysicsConstraintData data, Skeleton skeleton) {
 		if (data == null) throw new IllegalArgumentException("data cannot be null.");
 		if (skeleton == null) throw new IllegalArgumentException("skeleton cannot be null.");
 		this.data = data;
+		this.skeleton = skeleton;
 
 		nodes = new Array(data.nodes.size);
 		for (NodeData nodeData : data.nodes)
@@ -69,10 +75,10 @@ public class PhysicsConstraint implements Updatable {
 	}
 
 	/** Copy constructor. */
-	public PhysicsConstraint (PhysicsConstraint constraint, Skeleton skeleton) {
+	public PhysicsConstraint (PhysicsConstraint constraint) {
 		if (constraint == null) throw new IllegalArgumentException("constraint cannot be null.");
-		if (skeleton == null) throw new IllegalArgumentException("skeleton cannot be null.");
 		data = constraint.data;
+		skeleton = constraint.skeleton;
 
 		nodes = new Array(constraint.nodes.size);
 		for (Node node : constraint.nodes)
@@ -91,6 +97,9 @@ public class PhysicsConstraint implements Updatable {
 	}
 
 	public void setToSetupPose () {
+		remaining = 0;
+		lastTime = skeleton.time;
+
 		Object[] nodes = this.nodes.items;
 		for (int i = 0, n = this.nodes.size; i < n; i++)
 			((Node)nodes[i]).setToSetupPose();
@@ -110,7 +119,29 @@ public class PhysicsConstraint implements Updatable {
 
 	/** Applies the constraint to the constrained bones. */
 	public void update () {
-		// BOZO! - Physics.
+		Object[] nodes = this.nodes.items;
+		int nodeCount = this.nodes.size;
+		Vector2 temp = this.temp;
+		for (int i = 0; i < nodeCount; i++) {
+			Node node = (Node)nodes[i];
+			if (node.parentBone == null) continue;
+			node.parentBone.localToWorld(temp.set(node.data.x, node.data.y));
+			node.x = temp.x;
+			node.y = temp.y;
+		}
+
+		Object[] springs = this.springs.items;
+		int springCount = this.springs.size;
+
+		remaining += lastTime - skeleton.time;
+		lastTime = skeleton.time;
+		while (remaining > 0.016f) {
+			remaining -= 0.016f;
+			for (int i = 0; i < springCount; i++)
+				((Spring)springs[i]).update();
+			for (int i = 0; i < nodeCount; i++)
+				((Node)nodes[i]).update(this);
+		}
 	}
 
 	public Array<Node> getNodes () {

spine-libgdx/spine-libgdx/src/com/esotericsoftware/spine/PhysicsConstraintData.java

@@ -31,6 +31,7 @@ package com.esotericsoftware.spine;
 
 import static com.esotericsoftware.spine.utils.SpineUtils.*;
 
+import com.badlogic.gdx.math.Vector2;
 import com.badlogic.gdx.utils.Array;
 import com.badlogic.gdx.utils.Null;
 
@@ -111,9 +112,13 @@ public class PhysicsConstraintData extends ConstraintData {
 
 	static public class Node {
 		public final NodeData data;
-		public final @Null Bone parentBone;
-		public final Bone[] bones;
-		public float x, y, px, py, ax, ay;
+		public @Null Bone parentBone;
+		public Bone[] bones;
+		public float x, y, vx, vy, ax, ay;
+
+		Node (NodeData data) { // Editor.
+			this.data = data;
+		}
 
 		public Node (NodeData data, Skeleton skeleton) {
 			this.data = data;
@@ -134,8 +139,8 @@ public class PhysicsConstraintData extends ConstraintData {
 			arraycopy(node.bones, 0, bones, 0, bones.length);
 			x = node.x;
 			y = node.y;
-			px = node.px;
-			py = node.py;
+			vx = node.vx;
+			vy = node.vy;
 			ax = node.ax;
 			ay = node.ay;
 		}
@@ -143,11 +148,30 @@ public class PhysicsConstraintData extends ConstraintData {
 		public void setToSetupPose () {
 			x = data.x;
 			y = data.y;
-			px = x;
-			py = y;
+			vx = 0;
+			vy = 0;
 			ax = 0;
 			ay = 0;
 		}
+
+		public void update (PhysicsConstraint constraint) {
+			if (parentBone != null) {
+				vx = 0;
+				vy = 0;
+				ax = 0;
+				ay = 0;
+				return;
+			}
+			float friction = 0.98f;
+			vx += ax - constraint.wind / friction;
+			vy += ay - constraint.gravity / friction;
+			ax = 0;
+			ay = 0;
+			x += vx;
+			y += vy;
+			vx *= friction;
+			vy *= friction;
+		}
 	}
 
 	static public class SpringData {
@@ -159,10 +183,14 @@ public class PhysicsConstraintData extends ConstraintData {
 
 	static public class Spring {
 		public final SpringData data;
-		public final Node node1, node2;
-		public final Bone[] bones;
+		public Node node1, node2;
+		public Bone[] bones;
 		public float length, strength, damping;
 
+		Spring (SpringData data) { // Editor.
+			this.data = data;
+		}
+
 		public Spring (SpringData data, PhysicsConstraint constraint, Skeleton skeleton) {
 			this.data = data;
 
@@ -192,5 +220,34 @@ public class PhysicsConstraintData extends ConstraintData {
 			strength = data.strength;
 			damping = data.damping;
 		}
+
+		public void update () {
+			float strength = 1f;
+
+			float x = node2.x - node1.x, y = node2.y - node1.y;
+			float d = (float)Math.sqrt(Math.max(x * x + y * y, 0.00001f));
+			if (data.rope && d <= length) return;
+
+			Vector2 unit_vector = new Vector2(x / d, y / d);
+			float distance_error = unit_vector.dot(x, y) - length;
+			float distance_impulse = 0.33f * strength * distance_error;
+
+			float vx = node2.vx - node1.vx, vy = node2.vy - node1.vy;
+			float velocity_error = unit_vector.dot(vx, vy);
+			float velocity_impulse = 0.2f * velocity_error;
+
+			float impulse = -(distance_impulse + velocity_impulse);
+			Vector2 f = unit_vector.scl(impulse);
+
+			node1.ax -= f.x - vx * damping;
+			node1.ay -= f.y - vy * damping;
+			node2.ax += f.x - vx * damping;
+			node2.ay += f.y - vy * damping;
+
+			if (!data.stretch && node2.parentBone == null) {
+				node2.x = node1.x + length * x / d;
+				node2.y = node1.y + length * y / d;
+			}
+		}
 	}
 }

spine-libgdx/spine-libgdx/src/com/esotericsoftware/spine/Skeleton.java

@@ -60,8 +60,9 @@ public class Skeleton {
 	final Array<Updatable> updateCache = new Array();
 	@Null Skin skin;
 	final Color color;
-	float scaleX = 1, scaleY = 1;
 	float x, y;
+	float scaleX = 1, scaleY = 1;
+	float time;
 
 	public Skeleton (SkeletonData data) {
 		if (data == null) throw new IllegalArgumentException("data cannot be null.");
@@ -153,12 +154,15 @@ public class Skeleton {
 
 		physicsConstraints = new Array(skeleton.physicsConstraints.size);
 		for (PhysicsConstraint physicsConstraint : skeleton.physicsConstraints)
-			physicsConstraints.add(new PhysicsConstraint(physicsConstraint, this));
+			physicsConstraints.add(new PhysicsConstraint(physicsConstraint));
 
 		skin = skeleton.skin;
 		color = new Color(skeleton.color);
+		x = skeleton.x;
+		y = skeleton.y;
 		scaleX = skeleton.scaleX;
 		scaleY = skeleton.scaleY;
+		time = skeleton.time;
 
 		updateCache();
 	}
@@ -791,6 +795,22 @@ public class Skeleton {
 		this.y = y;
 	}
 
+	/** Returns the skeleton's time. This is used for time-based manipulations, such as {@link PhysicsConstraint}.
+	 * <p>
+	 * See {@link #update(float)}. */
+	public float getTime () {
+		return time;
+	}
+
+	public void setTime (float time) {
+		this.time = time;
+	}
+
+	/** Increments the skeleton's {@link #time}. */
+	public void update (float delta) {
+		time += delta;
+	}
+
 	public String toString () {
 		return data.name != null ? data.name : super.toString();
 	}