问题
I want to draw a texture on a body, which is a box. How do I convert the coordinates of the body to screen coordinates? I know that the other way around is with camera.unproject(pos), is it similar to this?
I see a lot of people using constants such as WORLD_TO_SCREEN = 32, but I currently don't have that in my game. Is that a problem, and how can I implement it now? Because it seems like people that are using these factors can convert world to screen positions easily. I currently have a camera and an ExtendViewport
camera = new OrthographicCamera(VIEWPORT_WIDTH, VIEWPORT_HEIGHT);
viewport = new ExtendViewport(VIEWPORT_WIDTH, VIEWPORT_HEIGHT, camera);
camera.position.set(VIEWPORT_WIDTH/2, VIEWPORT_HEIGHT/2, 0f);
Viewport width and height are set to this
public static final int VIEWPORT_WIDTH = 20;
public static final int VIEWPORT_HEIGHT = 22;
I don't really know what I'm doing, I read documentation and read some tutorials, but if someone could give some explanation about these variables and the world_to_screen factor that would really help me out.
I also set APP_WIDTH=1280, APP_HEIGHT = 720
Do viewport width and height mean that for box2d my screen is 20 meters wide and 22 meters high?
(asking it again because I added a lot the question and I would really like to know these things)
[EDIT]
So I'm trying to draw a ground picture on the ground body
float x = stage.getGround().getX();
float y = stage.getGround().getY();
float w = stage.getGround().getWidth();
float h = stage.getGround().getHeight();
stage.act(delta);
stage.draw();
stage.updateCamera();
Texture texture = new Texture(Gdx.files.internal("ground.png"));
Sprite sprite = new Sprite(texture);
sprite.setSize(w, h);
sprite.setPosition(x-sprite.getWidth()/2, y-sprite.getHeight()/2);
But I don't see it anywhere
[EDIT 2] Stage Class
public class Mission1Stage extends Stage{
public static final int VIEWPORT_WIDTH = 20;
public static final int VIEWPORT_HEIGHT = 22;
private World world;
private Ground ground;
private LeftWall leftWall;
private Rocket rocket;
private static final float TIME_STEP = 1 / 300f;
private float accumulator = 0f;
private OrthographicCamera camera;
private Box2DDebugRenderer renderer;
private Viewport viewport;
private SpriteBatch spriteBatch = new SpriteBatch();
private Vector3 touchPoint;
private ShapeRenderer shapeRenderer;
private Button boostButton;
private Skin boostSkin;
private Button boostLeftButton;
private Skin boostLeftSkin;
private Button boostRightButton;
private Skin boostRightSkin;
private Button resetButton;
private Skin resetSkin;
private Game game;
private boolean isTouched = false;
public Mission1Stage(Game game) {
setUpWorld();
renderer = new Box2DDebugRenderer();
shapeRenderer = new ShapeRenderer();
setupCamera();
setUpButtons();
addActor(new Background(ground));
}
private void setUpWorld() {
world = WorldUtils.createWorld();
setUpGround();
setUpRocket();
}
private void setUpGround() {
ground = new Ground(WorldUtils.createGround(world));
addActor(ground);
}
private void setUpLeftWall() {
leftWall = new LeftWall(WorldUtils.createLeftWall(world));
}
private void setUpRocket() {
rocket = new Rocket(WorldUtils.createRocket(world));
addActor(rocket);
}
private void setupCamera() {
camera = new OrthographicCamera(VIEWPORT_WIDTH, VIEWPORT_HEIGHT);
viewport = new ExtendViewport(VIEWPORT_WIDTH, VIEWPORT_HEIGHT, camera);
camera.position.set(VIEWPORT_WIDTH/2, VIEWPORT_HEIGHT/2, 0f);
camera.update();
}
private void setUpButtons() {
boostSkin = new Skin(Gdx.files.internal("skin/flat-earth-ui.json"));
boostButton = new Button(boostSkin);
boostButton.setSize(80,80);
boostButton.setPosition(Gdx.graphics.getWidth()-boostButton.getWidth()*2,0);
boostButton.setTransform(true);
boostButton.scaleBy(0.5f);
Gdx.input.setInputProcessor(this);
addActor(boostButton);
boostLeftSkin = new Skin(Gdx.files.internal("skin/flat-earth-ui.json"));
boostLeftButton = new Button(boostLeftSkin);
boostLeftButton.setSize(100, 100);
boostLeftButton.setPosition(0, 0);
addActor(boostLeftButton);
boostRightSkin = new Skin(Gdx.files.internal("skin/flat-earth-ui.json"));
boostRightButton = new Button(boostRightSkin);
boostRightButton.setSize(100, 100);
boostRightButton.setPosition(boostLeftButton.getWidth(), 0);
addActor(boostRightButton);
resetSkin = new Skin(Gdx.files.internal("skin/flat-earth-ui.json"));
resetButton = new Button(resetSkin);
resetButton.setSize(100, 100);
resetButton.setPosition(Gdx.graphics.getWidth()-100, Gdx.graphics.getHeight()-100);
addActor(resetButton);
}
@Override
public void act(float delta) {
super.act(delta);
handleInput();
accumulator += delta;
while(accumulator >= delta) {
world.step(TIME_STEP, 6, 2);
accumulator -= TIME_STEP;
}
}
@Override
public void draw() {
super.draw();
renderer.render(world, camera.combined);
float x = getGround().getBody().getPosition().x;
float y = getGround().getBody().getPosition().y;
float w = getGround().getWidth() * 2;
float h = getGround().getHeight() * 2;
spriteBatch.setProjectionMatrix(getCamera().combined);
Texture texture = new Texture(Gdx.files.internal("ground.png"));
Sprite sprite = new Sprite(texture);
sprite.setSize(w, h);
sprite.setPosition(x-sprite.getWidth()/2, y-sprite.getHeight()/2);
spriteBatch.begin();
sprite.draw(spriteBatch);
spriteBatch.end();
}
public void handleInput() {
if(boostButton.isPressed()) {
rocket.boost();
}
if(boostLeftButton.isPressed()) {
rocket.turnLeft();
}
if(boostRightButton.isPressed()) {
rocket.turnRight();
}
if(resetButton.isPressed()) {
}
}
public boolean resetScreen() {
if(resetButton.isPressed()) return true;
return false;
}
public void updateCamera() {
}
public Ground getGround() {
return ground;
}
public void resize(int width, int height) {
viewport.update(width, height);
camera.position.x = VIEWPORT_WIDTH / 2;
camera.position.y = VIEWPORT_HEIGHT /2;
}
private void translateScreenToWorldCoordinates(int x, int y) {
getCamera().unproject(touchPoint.set(x, y, 0));getCamera();
}
}
Screen class
public class Mission1Screen implements Screen{
private Game game;
private Mission1Stage stage;
private SpriteBatch spriteBatch = new SpriteBatch();
private Skin boostSkin;
private Button boostButton;
public Mission1Screen(Game game) {
this.game = game;
stage = new Mission1Stage(game);
}
@Override
public void show() {
}
@Override
public void render(float delta) {
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
if(stage.resetScreen()) {
game.setScreen(new Mission1Screen(game));
}
stage.act(delta);
stage.draw();
stage.updateCamera();
}
@Override
public void resize(int width, int height) {
stage.resize(width, height);
}
@Override
public void pause() {
}
@Override
public void resume() {
}
@Override
public void hide() {
}
@Override
public void dispose() {
}
}
[EDIT 3]
public class Main extends Game {
@Override
public void create () {
this.setScreen(new Mission1Screen(this));
}
@Override
public void render () {
super.render();
}
@Override
public void dispose () {
}
}
回答1:
We mostly use Pixel to meter conversion because box2d best works in meters (0-10) but you can avoid this conversion by using small worldwidth and height of your viewport. I mostly prefer 48 and 80 as viewport width and height.
You can use unproject(vector3) method of camera that translate a point given in screen coordinates to world space. I am using this method in touchdown because I get screen coordinate as parameter then I need to convert it into camera world space so that I can generate object at a particular position in world.
public class MyGdxTest extends Game implements InputProcessor {
private SpriteBatch batch;
private ExtendViewport extendViewport;
private OrthographicCamera cam;
private float w=20;
private float h=22;
private World world;
private Box2DDebugRenderer debugRenderer;
private Array<Body> array;
private Vector3 vector3;
@Override
public void create() {
cam=new OrthographicCamera();
extendViewport=new ExtendViewport(w,h,cam);
batch =new SpriteBatch();
Gdx.input.setInputProcessor(this);
world=new World(new Vector2(0,-9.8f),true);
array=new Array<Body>();
debugRenderer=new Box2DDebugRenderer();
vector3=new Vector3();
BodyDef bodyDef=new BodyDef();
bodyDef.type= BodyDef.BodyType.StaticBody;
bodyDef.position.set(0,0);
Body body=world.createBody(bodyDef);
ChainShape chainShape=new ChainShape();
chainShape.createChain(new float[]{1,1,55,1});
FixtureDef fixtureDef=new FixtureDef();
fixtureDef.shape=chainShape;
fixtureDef.restitution=.5f;
body.createFixture(fixtureDef);
chainShape.dispose();
}
@Override
public void render() {
super.render();
Gdx.gl.glClearColor(0,1,1,1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
world.step(1/60f,6,2);
batch.setProjectionMatrix(cam.combined);
batch.begin();
world.getBodies(array);
for (Body body:array){
if(body.getUserData()!=null) {
Sprite sprite = (Sprite) body.getUserData();
sprite.setPosition(body.getPosition().x-sprite.getWidth()/2, body.getPosition().y-sprite.getHeight()/2);
sprite.setRotation(body.getAngle()*MathUtils.radDeg);
sprite.draw(batch);
}
}
batch.end();
debugRenderer.render(world,cam.combined);
}
@Override
public void resize(int width, int height) {
super.resize(width,height);
extendViewport.update(width,height);
cam.position.x = w /2;
cam.position.y = h/2;
cam.update();
}
private void createPhysicsObject(float x,float y){
float sizeX=2,sizeY=2;
BodyDef bodyDef=new BodyDef();
bodyDef.position.set(x,y);
bodyDef.type= BodyDef.BodyType.DynamicBody;
Body body=world.createBody(bodyDef);
PolygonShape polygonShape=new PolygonShape();
polygonShape.setAsBox(sizeX,sizeY);
FixtureDef fixtureDef=new FixtureDef();
fixtureDef.shape=polygonShape;
fixtureDef.restitution=.2f;
fixtureDef.density=2;
body.createFixture(fixtureDef);
body.setFixedRotation(false);
polygonShape.dispose();
Sprite sprite=new Sprite(new Texture("badlogic.jpg"));
sprite.setSize(2*sizeX,2*sizeY);
sprite.setPosition(x-sprite.getWidth()/2,y-sprite.getHeight()/2);
sprite.setOrigin(sizeX,sizeY);
body.setUserData(sprite);
}
@Override
public void dispose() {
batch.dispose();
debugRenderer.dispose();
world.dispose();
}
@Override
public boolean keyDown(int keycode) {
return false;
}
@Override
public boolean keyUp(int keycode) {
return false;
}
@Override
public boolean keyTyped(char character) {
return false;
}
@Override
public boolean touchDown(int screenX, int screenY, int pointer, int button) {
vector3.set(screenX,screenY,0);
Vector3 position=cam.unproject(vector3);
createPhysicsObject(vector3.x,vector3.y);
return false;
}
@Override
public boolean touchUp(int screenX, int screenY, int pointer, int button) {
return false;
}
@Override
public boolean touchDragged(int screenX, int screenY, int pointer) {
return false;
}
@Override
public boolean mouseMoved(int screenX, int screenY) {
return false;
}
@Override
public boolean scrolled(int amount) {
return false;
}
}
来源：https://stackoverflow.com/questions/43408764/libgdx-world-to-screen-pos-and-factors