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

/******************************************************************************
 * Spine Runtimes License Agreement
 * Last updated April 5, 2025. Replaces all prior versions.
 *
 * Copyright (c) 2013-2025, Esoteric Software LLC
 *
 * Integration of the Spine Runtimes into software or otherwise creating
 * derivative works of the Spine Runtimes is permitted under the terms and
 * conditions of Section 2 of the Spine Editor License Agreement:
 * http://esotericsoftware.com/spine-editor-license
 *
 * Otherwise, it is permitted to integrate the Spine Runtimes into software
 * or otherwise create derivative works of the Spine Runtimes (collectively,
 * "Products"), provided that each user of the Products must obtain their own
 * Spine Editor license and redistribution of the Products in any form must
 * include this license and copyright notice.
 *
 * THE SPINE RUNTIMES ARE PROVIDED BY ESOTERIC SOFTWARE LLC "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL ESOTERIC SOFTWARE LLC BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES,
 * BUSINESS INTERRUPTION, OR LOSS OF USE, DATA, OR PROFITS) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THE SPINE RUNTIMES, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *****************************************************************************/

package com.esotericsoftware.spine;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.backends.lwjgl3.Lwjgl3Application;
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.badlogic.gdx.utils.ScreenUtils;

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);
	}

	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.
		float delta = Gdx.graphics.getDeltaTime();
		state.update(delta);
		state.apply(skeleton);
		skeleton.update(delta);
		// This example has no physics, but if it did we first pose the skeleton without physics.
		skeleton.updateWorldTransform(Physics.pose);

		// 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().getAppliedPose().worldToLocal(boneCoords); // camera space to local bone space
		crosshair.getPose().setPosition(boneCoords.x, boneCoords.y); // override the crosshair position

		// Calculate final world transform with the crosshair bone set to the mouse cursor position. Update physics this time.
		skeleton.updateWorldTransform(Physics.update);

		// Clear the screen, update the camera and render the skeleton.
		ScreenUtils.clear(0, 0, 0, 0);
		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();
	}

	static public void main (String[] args) throws Exception {
		new Lwjgl3Application(new IKTest());
	}
}