Develop Reference

Attaching a sprite to a Box2d body for movement

Im new on Box2d got a problem and couldnt solve it.
I want to move my player left and right when the user touch my left and right buttons.
I created a fixture I can move body and fixture but not the player sprite
How can I attach my player sprite to my body ?
and How should I control body because I cant stop it.
I want to find a proper way of controlling player in box2d. I couldnt use setLinerVelocity etc.
this is my codes
public World world;
public Body bplayer;
public Box2DDebugRenderer b2dr;
public Matrix4 cameraBox2D;
PlayScreen
buttonimage.addListener(new ClickListener() {
public boolean touchDown(InputEvent event, float x, float y, int pointer, int button)
{
bplayer.setLinearVelocity(-5*PPM , 0);
return true;
}
});
world = new World(new Vector2(player.getPosition().x , player.getPosition().y) , false);
b2dr = new Box2DDebugRenderer();
bplayer = createPlayer(player.getPosition().x , player.getPosition().y);
show method
buttonimage.setPosition(160,0);
rightbuttonimage.setPosition(320,0);
pauseimage.setPosition(220,-20);
cameraBox2D = camera.combined.cpy();
Render method
Gdx.gl.glClearColor(0, 0, 2f, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
sb.setProjectionMatrix(camera.combined);
player.position.y += 500 * Gdx.graphics.getDeltaTime();
sb.begin();
sb.draw(bg, 0, camera.position.y - (camera.viewportHeight/2));
sb.draw(player.sprite, player.getPosition().x , player.getPosition().y);
for (Tube tube : tubes) {
sb.draw(tube.getlefttube(), tube.getposlefttube().x, tube.getposlefttube().y);
sb.draw(tube.getrighttube(), tube.getposrighttube().x, tube.getposrighttube().y);
sb.draw(tube.getLight() , tube.getPoslight().x , tube.getPoslight().y);
}
delta*=speed;
sb.end();
update(delta);
b2dr.render(world , cameraBox2D);
stage.draw();
app.batch.begin();
app.font23.draw(app.batch,"Lights collected :" + dropsGathered , 0, 720);
app.batch.end();
cameraUpdate method
Vector3 position = camera.position;
position.x = player.position.x;
position.y = player.position.y;
camera.position.set(position);
createPlayer method
Body pBody;
BodyDef def = new BodyDef();
def.type = BodyDef.BodyType.DynamicBody;
def.position.set(x * PPM, y * PPM );
def.fixedRotation = true;
pBody = world.createBody(def);
return pBody;
update method
world.step(1 / 60f , 6 , 2);
for(int i = 0; i < tubes.size; i++) {
Tube tube = tubes.get(i);
if (camera.position.y - (camera.viewportWidth/2) > tube.getposlefttube().y + tube.getlefttube().getWidth()) {
tube.reposition(tube.getposlefttube().y + ( TUBE_COUNT) );
}
if (tube.collides(player.getBounds())){
app.setScreen(new GameOver(app));
}
if (tube.gathered(player.getBounds())){
dropsGathered++;
}
if (dropsGathered >= 50){
//app.setScreen(new Stage2(app));
}
}
camera.update();
handleInput();
camera.position.y = player.getPosition().y + 300;
player.update(delta);
camera.update();
cameraUpdate(delta);
stage.act(delta);

Do not use the Sprite class. Use the TextureRegion class instead. Sprite is confusingly subclassed from TextureRegion, so when you call batch.draw(sprite, ...) its position and rotation parameters are ignored because it is being treated as a TextureRegion.
You could use a Sprite by calling sprite.draw(batch) but a Sprite is redundant because your Body already has position and rotation parameters.
Use a TextureRegion directly with the SpriteBatch. You can orient it with rotation parameters passed into the draw method.

Cocos2d-X: CCDrawNode draw circle/custom shape

I am using CCDrawNode to create mask type effect (not exactly mask). Everything works well but there is one problem that CCDrawNode only draws square and i want to draw it with custom texture/sprite. Is there any solution to it.
Below is my code of using CCDrawNode
// on "init" you need to initialize your instance
bool HelloWorld::init()
{
//////////////////////////////
// 1. super init first
if ( !CCLayer::init() )
{
return false;
}
CCSize visibleSize = CCDirector::sharedDirector()->getVisibleSize();
CCPoint origin = CCDirector::sharedDirector()->getVisibleOrigin();
CCLayer *layer = CCLayer::create();
CCSprite* pSprite = CCSprite::create("HelloWorld.png");
pSprite->setPosition(ccp(visibleSize.width/2 + origin.x, visibleSize.height/2 + origin.y));
layer->addChild(pSprite, 0);
addChild(layer);
//this is the layer that we want to "cut"
CCLayer* layer1 = CCLayerColor::create(ccc4(122, 144, 0, 255), visibleSize.width, visibleSize.height);
this->setTouchEnabled(true);
//we need to create a ccnode, which will be a stencil for ccclipingnode, draw node is a good choice for that
stencil = CCDrawNode::create();
//CCClipingNode show the intersection of stencil and theirs children
CCClippingNode *cliper = CCClippingNode::create(stencil);
cliper->setInverted(true);
cliper->addChild(layer1);
addChild(cliper);
return true;
}
void HelloWorld::ccTouchesMoved(CCSet* touches, CCEvent* event)
{
CCTouch* touch = (CCTouch*)touches->anyObject();
// get start & end location
CCPoint start = touch->getLocationInView();
CCPoint end = touch->getPreviousLocationInView();
// get corrected location
start = CCDirector::sharedDirector()->convertToGL(start);
end = CCDirector::sharedDirector()->convertToGL(end);
//stencil->drawDot(start, 25, ccc4f(0, 0, 0, 255));
stencil->drawSegment(start, end, 25, ccc4f(0, 0, 0, 255));
}

If you want to draw custom texture you should use CCRenderTexture. In order to draw something you should go smthin like this
myRenderTexture->begin();
mySpriteLoadedWithTexture->visit();
myRenderTexture->end();
Also if you want the drawn lines to be smooth you should draw it in loop so that they are placed in equal distance
float distance = ccpDistance(start, end);
for (int i = 0; i < distance; i++)
{
float difx = end.x - start.x;
float dify = end.y - start.y;
float delta = (float)i / distance;
m_brush->setPosition(CCPoint(start.x + (difx * delta), start.y + (dify * delta)));
m_brush->visit();
}
Hope it helps

ShowCaseView Incorrectly rendering

I am using showCaseView legacy(which has the animation of the hand) in my android app. But, the gesture doesnt seem to start 'relative' to the view. Instead, it seems to be absolute to the screen. This is the following which i am using:
final ShowcaseView sv;
ShowcaseView.ConfigOptions co = new ShowcaseView.ConfigOptions();
co.hideOnClickOutside = false;
co.block=true;
sv = ShowcaseView.insertShowcaseView(R.id.pen, this," R.string.showcase_title"," R.string.showcase_message", co);
View v=(View)findViewById(R.id.pen);
sv.animateGesture(0, 0, 0, -500, false);
This is the top of my emulator, the animation STARTS from here:
This shows a hand at the top left corner of the screen. (my guess is that the view's locations are being returned 0.
What is the problem ?

Your best bet is probably going to be to use DisplayMetrics to place the hand, that's what I've done and it seems to work well.
DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
int height = displaymetrics.heightPixels;
int width = displaymetrics.widthPixels;
float offsetEndY = height / 2 + 50;
float offsetEndX = -width;
float offsetStartY = height / 2 + 50;
float offsetStartX = -width / 2;
if (sv == null) {
sv = ShowcaseView.insertShowcaseView(width, 0, activity, "Menu", "Swipe to access more options", mOptions)
.setTextColors(Color.BLUE, Color.BLACK);
sv.animateGesture(offsetStartX, offsetStartY, offsetEndX, offsetEndY);

I had the same problem and I from logging showcase positions at different stages I found that proper position is strangely calculated some (very short) time after show() is called.
When I was calling
showcaseView.show();
showcaseView.animateGesture(0, 0, 0, -400);
this DIDN'T work.
Easy solution is show hand gesture with some delay (200 ms was enough in my case - tested on many devices):
showcaseView.show();
showcaseView.postDelayed(new Runnable() {
#Override
public void run() {
showcaseView.animateGesture(0, 0, 0, -400);
}
}, 200);

Infinite Scrolling Texture

I am using the libgdx framework and trying to repeat a background of spikes forever. The issue I am having is that the texture is moving extremely fast forever, but I want to slow it down. I was looking at a tutorial from Google Code and another user had this same issue. The "supposed" solution was this:
if(scrollTimer>1.0f)
scrollTimer = 0.0f;
scrollTimer = 3f;
This was to make it scroll 3 times faster, so I attempted this and substituted 0.3f instead of 3f, but this makes the background at a standstill.
Here is some relevant code that might help in solving this issue:
public class PlayScreen implements Screen{
final Rectangle upSpikeBounds = new Rectangle(0,0,Gdx.graphics.getWidth() * 2, 25);
final Rectangle downSpikeBounds = new Rectangle(0,Gdx.graphics.getHeight() - 25,Gdx.graphics.getWidth() * 2, 25);
Rectangle blockBounds;
float total_time = 0f;
Sprite spikeUpSprite, spikeDownSprite, spriteBlock;
public PlayScreen(Game game){
batch = new SpriteBatch();
player = new Player(new Vector2(Gdx.graphics.getWidth()/10, Gdx.graphics.getHeight()/2), batch);
stage = new Stage();
this.game = game;
Texture spikeUp = new Texture(Gdx.files.internal("spikes.png"));
Texture spikeDown = new Texture(Gdx.files.internal("spikes.png"));
spikeUp.setWrap(TextureWrap.Repeat, TextureWrap.Repeat);
spikeDown.setWrap(TextureWrap.Repeat, TextureWrap.Repeat);
spikeUpSprite = new Sprite(spikeUp, 0, 0, Gdx.graphics.getWidth(), 25);
spikeDownSprite = new Sprite(spikeDown, 0, 25, Gdx.graphics.getWidth(), -25);
spikeDownSprite.setPosition(0, Gdx.graphics.getHeight() - 20);
spikeUpSprite.setSize(1200, 25);
spikeDownSprite.setSize(1200, 25);
}
public void render(float deltaTime) {
Gdx.gl.glClearColor(1, 1, 1, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
label.setText("Score: " + player.score);
cam.position.set(player.getPosition().x + Gdx.graphics.getWidth()/2,Gdx.graphics.getHeight () / 2,0);
batch.setProjectionMatrix(cam.combined);
cam.update();
total_time += Gdx.graphics.getDeltaTime();
if (total_time > 1.0f){
total_time = 0.0f;
}
spikeUpSprite.setU(total_time);
spikeUpSprite.setU2((total_time+1));
spikeDownSprite.setU(total_time);
spikeDownSprite.setU2(total_time+1);
stage.act();
batch.begin();
spikeUpSprite.draw(batch);
spikeDownSprite.draw(batch);
batch.end();
stage.draw();
}
}
Can anyone help me?

You should look up the tween engine, it will enable you to use 'tween animation', which is an animation of values, who with a duration. For instance if you animate from zero to 700 with a 700ms duration, the value will start from zero and increase by 1 every ms

While micnubinub's answer is certainly interesting and worth checking out, I have figured out a quick fix for my issue. The problem lies in this line:
total_time += Gdx.graphics.getDeltaTime();
This is where the speed of the background lies. Because delta time is so fast (probably to the microsecond), the background scrolls by too fast. If I change it to a manual number, such as 0.0093f, I get a background that scrolls at the speed I desire.

LibGDX PhysicsBox2D, if i set linear velocity, physics does not work correctly

my world is world = new World(new Vector2(0, 0), true); //there is no gravity
and i have walls in the left, right, top bottom of the screen, so elements do not fly off the display.
I have the following code in my render class:
Gdx.gl.glClearColor(0, 0, 0.2f, 1);
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
camera.update();
Box2DDebugRenderer debugRenderer = new Box2DDebugRenderer();
batch.setProjectionMatrix(camera.combined);
batch.begin();
batch.draw(texture, 0, 0);
for (Element element : elements) {
element.body.setUserData(element);
element.rect.x = element.body.getPosition().x-16;//16 = half the width of element
element.rect.y = element.body.getPosition().y-16;
if (element.goodOrEvil == 0) {
batch.draw(happyImage, element.rect.x, element.rect.y);
} else if (element.goodOrEvil == 1) {
batch.draw(sadImage, element.rect.x, element.rect.y);
}
} //i draw the elements that i have to fix the bodies to
batch.end();
debugRenderer.render(world, camera.combined);
Iterator<Element> iter = elements.iterator();
//next i set the accelerometer to move the elements, so that i could control them, i need to move all the elements in the same direction, in the same time
while (iter.hasNext()) {
Element element = iter.next();
element.body.setLinearVelocity(Gdx.input.getAccelerometerY() * 50, -Gdx.input.getAccelerometerX() * 50);
}
if (TimeUtils.nanoTime() - lastDropTime > 1000000000)
spawnElement(); // this creates a new element
world.step(1 / 45f, 6, 2);
Here is my spawnElement() class:
private void spawnElement() {
Rectangle elementRect = new Rectangle();
elementRect.x = MathUtils.random(0, 800 - 32);
elementRect.y = 400;
elementRect.width = 32;
elementRect.height = 32;
Element element = new Element(elementRect, (int) elementRect.x % 2);
elements.add(element);
// First we create a body definition
BodyDef bodyDef = new BodyDef();
// We set our body to dynamic, for something like ground which doesnt
// move we would set it to StaticBody
bodyDef.type = BodyType.DynamicBody;
// Set our body's starting position in the world
bodyDef.position.set(elementRect.x, elementRect.y);
// Create our body in the world using our body definition
body = world.createBody(bodyDef);
// Create a circle shape and set its radius to 6
CircleShape circle = new CircleShape();
circle.setRadius(6f);
// Create a fixture definition to apply our shape to
FixtureDef fixtureDef = new FixtureDef();
fixtureDef.shape = circle;
fixtureDef.density = 0.5f;
fixtureDef.friction = 0.4f;
fixtureDef.restitution = 0.6f; // Make it bounce a little bit
// Create our fixture and attach it to the body
Fixture fixture = body.createFixture(fixtureDef);
element.body = body;
lastDropTime = TimeUtils.nanoTime();
}
Now if i set gravity to exist world = new World(new Vector2(-2, -20), true); and comment out this line: element.body.setLinearVelocity(Gdx.input.getAccelerometerY() * 50, -Gdx.input.getAccelerometerX() * 50); the physics works great, but i cannot control my objects. If i leave the code as it is (no gravity and that line in), i can control my objects, but when an element hits the wall, and another element comes, they overlap, and only then start to divide. I need them to hit one another, and remain close, but not overlap at all. Any ideea on how this could be made?

instead of using element.body.setLinearVelocity(Gdx.input.getAccelerometerY() * 50, -Gdx.input.getAccelerometerX() * 50);
i have used this:
Vector2 gravity = new Vector2(Gdx.input.getAccelerometerY() * 50, -Gdx.input.getAccelerometerX() * 50);
world.setGravity(gravity);
And then it answers just like when i set a static gravity, but i change the gravity at every render, with values from my accelerometer