[libgdx] Added mouse following IK example. See #1532.

spine-libgdx/spine-libgdx-tests/src/com/esotericsoftware/spine/IKTest.java

@@ -0,0 +1,128 @@
+package com.esotericsoftware.spine;
+
+import com.badlogic.gdx.ApplicationAdapter;
+import com.badlogic.gdx.Gdx;
+import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
+import com.badlogic.gdx.graphics.GL20;
+import com.badlogic.gdx.graphics.OrthographicCamera;
+import com.badlogic.gdx.graphics.g2d.TextureAtlas;
+import com.badlogic.gdx.math.Vector2;
+import com.badlogic.gdx.math.Vector3;
+import com.esotericsoftware.spine.utils.TwoColorPolygonBatch;
+
+/** Demonstrates how to let the target bone of an IK constraint
+ * follow the mouse or touch position, which in turn repositions
+ * part of the skeleton, in this case Spineboy's back arm including
+ * his gun.
+ */
+public class IKTest extends ApplicationAdapter {
+	OrthographicCamera camera;
+	TwoColorPolygonBatch batch;
+	SkeletonRenderer renderer;
+
+	TextureAtlas atlas;
+	Skeleton skeleton;
+	AnimationState state;
+	
+	Vector3 cameraCoords = new Vector3();
+	Vector2 boneCoords = new Vector2();
+
+	public void create () {
+		// Create objects needed for rendering
+		camera = new OrthographicCamera();
+		batch = new TwoColorPolygonBatch();
+		renderer = new SkeletonRenderer();
+		renderer.setPremultipliedAlpha(true);
+
+		// Load the texture atlas and skeleton data
+		atlas = new TextureAtlas(Gdx.files.internal("spineboy/spineboy-pma.atlas"));
+		SkeletonBinary json = new SkeletonBinary(atlas);
+		json.setScale(0.6f);		
+		SkeletonData skeletonData = json.readSkeletonData(Gdx.files.internal("spineboy/spineboy-pro.skel"));
+
+		// Create a skeleton from the skeleton data
+		skeleton = new Skeleton(skeletonData);
+		skeleton.setPosition(250, 20);
+		
+		// Create an animation satte
+		AnimationStateData stateData = new AnimationStateData(skeletonData);
+		state = new AnimationState(stateData);
+		
+		// Queue the "walk" animation on the first track.
+		state.setAnimation(0, "walk", true);
+		
+		// Queue the "aim" animation on a higher track. 
+		// It consists of a single frame that positions
+		// the back arm and gun such that they point at
+		// the "crosshair" bone. By setting this
+		// animation on a higher track, it overrides
+		// any changes to the back arm and gun made
+		// by the walk animation, allowing us to
+		// mix the two. The mouse position following
+		// is performed in the render() method below.
+		state.setAnimation(1, "aim", true);
+		
+		// apply the state once, so we have world
+		// bone positions that we can use.
+		skeleton.setToSetupPose();
+	}
+
+	public void render () {
+		// Update and apply the animations to the skeleton,
+		// then calculate the world transforms of every bone.
+		// This is needed so we can call Bone#worldToLocal()
+		// later.
+		state.update(Gdx.graphics.getDeltaTime());		
+		state.apply(skeleton);
+		skeleton.updateWorldTransform();
+		
+		// Position the "crosshair" bone at the mouse
+		// location. We do this before calling
+		// skeleton.updateWorldTransform() below, so
+		// our change is incorporated before the IK
+		// constraint is applied.
+		//
+		// When setting the crosshair bone position
+		// to the mouse position, we need to translate
+		// from "mouse space" to "camera space"
+		// and then to "local bone space". Note that the local 
+		// bone space is calculated using the bone's parent
+		// worldToLocal() function!
+		cameraCoords.set(Gdx.input.getX(), Gdx.input.getY(), 0);
+		camera.unproject(cameraCoords); // mouse space to camera space		
+		
+		Bone crosshair = skeleton.findBone("crosshair"); // Should be cached.
+		boneCoords.set(cameraCoords.x, cameraCoords.y);
+		crosshair.getParent().worldToLocal(boneCoords); // camera space to local bone space
+		crosshair.setPosition(boneCoords.x, boneCoords.y); // override the crosshair position
+		crosshair.setAppliedValid(false);
+		
+		// Calculate final world transform with the
+		// crosshair bone set to the mouse cursor
+		// position.
+		skeleton.updateWorldTransform();
+
+		// Clear the screen, update the camera and
+		// render the skeleton.
+		Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
+		camera.update();
+		
+		batch.getProjectionMatrix().set(camera.combined);
+		batch.begin();
+		renderer.draw(batch, skeleton);
+		batch.end();
+
+	}
+
+	public void resize (int width, int height) {
+		camera.setToOrtho(false); // Update camera with new size.
+	}
+
+	public void dispose () {
+		atlas.dispose();
+	}
+
+	public static void main (String[] args) throws Exception {
+		new LwjglApplication(new IKTest());
+	}
+}