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That is a version of loader for physic-body-editor that works with new JSON API from libgdx nightlies.
package aurelienribon.bodyeditor;
import com.badlogic.gdx.files.FileHandle;
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.CircleShape;
import com.badlogic.gdx.physics.box2d.FixtureDef;
import com.badlogic.gdx.physics.box2d.PolygonShape;
import com.badlogic.gdx.utils.Array;
import com.badlogic.gdx.utils.JsonReader;
import com.badlogic.gdx.utils.JsonValue;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
* Loads the collision fixtures defined with the Physics Body Editor
* application. You only need to give it a body and the corresponding fixture
* name, and it will attach these fixtures to your body.
* @author Aurelien Ribon |
public class BodyEditorLoader {
// Model
private final Model model;
// Reusable stuff
private final List<Vector2> vectorPool = new ArrayList<Vector2>();
private final PolygonShape polygonShape = new PolygonShape();
private final CircleShape circleShape = new CircleShape();
private final Vector2 vec = new Vector2();
// -------------------------------------------------------------------------
// Ctors
// -------------------------------------------------------------------------
public BodyEditorLoader(FileHandle file) {
if (file == null) throw new NullPointerException("file is null");
model = readJson(file.readString());
public BodyEditorLoader(String str) {
if (str == null) throw new NullPointerException("str is null");
model = readJson(str);
// -------------------------------------------------------------------------
// Public API
// -------------------------------------------------------------------------
* Creates and applies the fixtures defined in the editor. The name
* parameter is used to retrieve the right fixture from the loaded file.
* <br/><br/>
* The body reference point (the red cross in the tool) is by default
* located at the bottom left corner of the image. This reference point
* will be put right over the BodyDef position point. Therefore, you should
* place this reference point carefully to let you place your body in your
* world easily with its BodyDef.position point. Note that to draw an image
* at the position of your body, you will need to know this reference point
* (see {@link #getOrigin(java.lang.String, float)}.
* <br/><br/>
* Also, saved shapes are normalized. As shown in the tool, the width of
* the image is considered to be always 1 meter. Thus, you need to provide
* a scale factor so the polygons get resized according to your needs (not
* every body is 1 meter large in your game, I guess).
* @param body The Box2d body you want to attach the fixture to.
* @param name The name of the fixture you want to load.
* @param fd The fixture parameters to apply to the created body fixture.
* @param scale The desired scale of the body. The default width is 1.
public void attachFixture(Body body, String name, FixtureDef fd, float scale) {
RigidBodyModel rbModel = model.rigidBodies.get(name);
if (rbModel == null) throw new RuntimeException("Name '" + name + "' was not found.");
Vector2 origin = vec.set(rbModel.origin).mul(scale);
for (int i=0, n=rbModel.polygons.size(); i<n; i++) {
PolygonModel polygon = rbModel.polygons.get(i);
Vector2[] vertices = polygon.buffer;
for (int ii=0, nn=vertices.length; ii<nn; ii++) {
vertices[ii] = newVec().set(polygon.vertices.get(ii)).mul(scale);
fd.shape = polygonShape;
for (int ii=0, nn=vertices.length; ii<nn; ii++) {
for (int i=0, n=rbModel.circles.size(); i<n; i++) {
CircleModel circle = rbModel.circles.get(i);
Vector2 center = newVec().set(;
float radius = circle.radius * scale;
fd.shape = circleShape;
* Gets the image path attached to the given name.
public String getImagePath(String name) {
RigidBodyModel rbModel = model.rigidBodies.get(name);
if (rbModel == null) throw new RuntimeException("Name '" + name + "' was not found.");
return rbModel.imagePath;
* Gets the origin point attached to the given name. Since the point is
* normalized in [0,1] coordinates, it needs to be scaled to your body
* size. Warning: this method returns the same Vector2 object each time, so
* copy it if you need it for later use.
public Vector2 getOrigin(String name, float scale) {
RigidBodyModel rbModel = model.rigidBodies.get(name);
if (rbModel == null) throw new RuntimeException("Name '" + name + "' was not found.");
return vec.set(rbModel.origin).mul(scale);
* <b>For advanced users only.</b> Lets you access the internal model of
* this loader and modify it. Be aware that any modification is permanent
* and that you should really know what you are doing.
public Model getInternalModel() {
return model;
// -------------------------------------------------------------------------
// Json Models
// -------------------------------------------------------------------------
public static class Model {
public final Map<String, RigidBodyModel> rigidBodies = new HashMap<String, RigidBodyModel>();
public static class RigidBodyModel {
public String name;
public String imagePath;
public final Vector2 origin = new Vector2();
public final List<PolygonModel> polygons = new ArrayList<PolygonModel>();
public final List<CircleModel> circles = new ArrayList<CircleModel>();
public static class PolygonModel {
public final List<Vector2> vertices = new ArrayList<Vector2>();
private Vector2[] buffer; // used to avoid allocation in attachFixture()
public static class CircleModel {
public final Vector2 center = new Vector2();
public float radius;
// -------------------------------------------------------------------------
// Json reading process
// -------------------------------------------------------------------------
private Model readJson(String str) {
Model m = new Model();
JsonValue map = new JsonReader().parse(str);
JsonValue bodyElem = map.getChild("rigidBodies");
for (; bodyElem != null; bodyElem = {
RigidBodyModel rbModel = readRigidBody(bodyElem);
m.rigidBodies.put(, rbModel);
return m;
private RigidBodyModel readRigidBody(JsonValue bodyElem) {
RigidBodyModel rbModel = new RigidBodyModel(); = bodyElem.getString("name");
rbModel.imagePath = bodyElem.getString("imagePath");
JsonValue originElem = bodyElem.get("origin");
rbModel.origin.x = originElem.getFloat("x");
rbModel.origin.y = originElem.getFloat("y");
// polygons
JsonValue polygonsElem = bodyElem.getChild("polygons");
for (; polygonsElem != null ;polygonsElem ={
PolygonModel polygon = new PolygonModel();
JsonValue vertexElem = polygonsElem.child();
for (; vertexElem != null; vertexElem = {
float x = vertexElem.getFloat("x");
float y = vertexElem.getFloat("y");
polygon.vertices.add(new Vector2(x, y));
polygon.buffer = new Vector2[polygon.vertices.size()];
// circles
JsonValue circleElem = bodyElem.getChild("circles");
for (; circleElem != null; circleElem = {
CircleModel circle = new CircleModel();
rbModel.circles.add(circle); = circleElem.getFloat("cx"); = circleElem.getFloat("cy");
circle.radius = circleElem.getFloat("r");
return rbModel;
// -------------------------------------------------------------------------
// Helpers
// -------------------------------------------------------------------------
private Vector2 newVec() {
return vectorPool.isEmpty() ? new Vector2() : vectorPool.remove(0);
private void free(Vector2 v) {

Have you sent a patch to the original author with this? A lot of people could benefit from it :-D. Some are asking about the incompatibilities between the new JSON API and the BodyEditorLoader in the libgdx forums. I myself encountered the same problem during the last Ludum Dare.


zudov commented May 19, 2013

Yes. I attached it to issue on google-code.
Here it is

Thank you very much for this patch ! Keep on the good work.


ghost commented May 5, 2014

there is a problem with this one,

float radius = circle.radius * scale;

it says, it is undefined for the argument types, float matrix3


mul function is matrix3 function, and it is not applicaple in float format, It does not work on new libgdx releases, can you fix this issue ?

grulg commented May 28, 2014

As of this change to libGDX's Vector2 API, the Vector2#mul(float) has been changed to Vector2#scl(float) instead.

It's an easy fix. I forked this Gist and fixed it, you can find it here.

Do you have a newer physic-body-editor for libgdx 1.2.0 ?

Grulg'x is working for me!


zudov commented Feb 23, 2016

I haven't been using libgdx or physics-body-editor for last three years, so I have no idea what's going on there or here.

If someone still experiences problems with that, they can give a try to @grulg's fork. According to comments it seem to work on newer version.
Or just find some alternative solution, where you won't have to fix the problems which are persisted over a few years.
Or help maintaining physics-body-editor properly, since apparently the breaking version of libgdx isn't nightly anymore.

If anyone do need an adapted version for org.jbox2d check my fork.

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