Develop Reference

libGDX Draw viewport only partly while cutting off the rest

This problem seemed very obvious for me to solve, but whatever I try, it doesn't work. What I'm trying to do is to incorporate a mini-version of my PlayScreen in a ScrollPane as a tutorial where you can read text and try it out immediately.
Because I didn't find any better solution to add this to the Table inside the ScrollPane, I edited the draw() method of the PlayScreen to take the ScrollPane.getScrollPercentY() and offset the camera of the PlayScreen accordingly.
What I want to do now is to only render only part of the viewport that would be normally visible in the real game. Subsequently, I want to be able to control the size and position of this "window".
I also want to be able to resize and move the content, while cutting off the edges that are not visible to the camera. This is what I tried inside the PlayScreenDraw:
public void draw(final float yOffset,
final int xTiles,
final int yTiles) {
view.getCamera().position.y = yTiles / 2f - yOffset * yTiles / HEIGHT; // HEIGHT = 800
view.getCamera().position.x = xTiles / 2f;
view.setWorldSize(xTiles, yTiles); //Do i even need to change the world size?
b.setProjectionMatrix(view.getCamera().combined);
b.begin();
...
b.end();
view.update(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
}
What this gives me, in terms of the picture above, is this
How do I need to change the viewport and/or the camera? Btw., this is how i set the two up:
cam = new OrthographicCamera();
cam.setToOrtho(false, WIDTH, HEIGHT); // WIDTH = 8, HEIGHT = 16
batch.setProjectionMatrix(cam.combined);
view = new FitViewport(WIDTH, HEIGHT, cam);

The Pixmap class can help you achieve what you want since you stated that you wanted to "cut off" the parts outside of the green selection box.
You need to render what the camera sees to an FBO and then get the pixmap from the FBO itself.
Framebuffer Objects are OpenGL Objects, which allow for the creation of user-defined Framebuffers. With them, one can render to non-Default Framebuffer locations, and thus render without disturbing the main screen.
-- OpenGL wiki
// Construct an FBO and keep a reference to it. Remember to dispose of it.
FrameBuffer fbo = new FrameBuffer(Format.RGBA8888, width, height, false);
public void render() {
//Start rendering to the fbo.
fbo.begin();
//From the camera's perspective.
batch.setProjectionMatrix(camera.combined);
batch.begin();
//Draw whatever you want to draw with the camera.
batch.end();
// Finished drawing, get pixmap.
Pixmap pixmap = ScreenUtils.getFrameBufferPixmap(0, 0, width, height);
//Stop drawing to your fbo.
fbo.end();
}
After getting the pixmap you can iterate through the pixels and set the alpha of the pixels outside your green selection window to 0 making them invisible or "cutting them off"

Attaching body to SpriteBatch

Im trying to get a SpriteBatch drawn to sync up to the position of a body.
Im not sure if this is the proper way to do this (in andengine you would just use physics connectors) But i tried drawing the sprite at the position the body was storing.
Gdx.gl.glClearColor(1, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
camera.update();
elapsedTime += Gdx.graphics.getDeltaTime();
batch.setProjectionMatrix(camera.combined);
batch.begin();
batch.draw(walkAnimation.getKeyFrame(elapsedTime, true),
mrsaiBody.getPosition().x, mrsaiBody.getPosition().y, width/2, height/2);
batch.end();
mWorld.step(1/30f, 6, 2);
mRenderer.render(mWorld, camera.combined);
The problem im having with this is, on the screen i see mrsaiBody's shape and i see the ground i made. When the shape makes contact with the ground the x and y values still continue to be affected by gravity even though the shape isnt. How can i get the current position of this shape to match up with position when i use batch.draw?

Using filledcircle and pixmap in libgdx

I am using Libgdx.
I want to simulate fog in my game using pixmap, but I have a problem during generating the "fogless" circle. First, I make a pixmap, filled with black (it is transparent a little bit). After filling I want to draw a filled circle onto it, but the result is not that I expected.
this.pixmap = new Pixmap(640, 640, Format.LuminanceAlpha);
Pixmap.setBlending(Blending.None); // disable Blending
this.pixmap.setColor(0, 0, 0, 0.9f);
this.pixmap.fill();
//this.pixmap.setColor(0, 0, 0, 0);
this.pixmap.fillCircle(200, 200, 100);
this.pixmapTexture = new Texture(pixmap, Format.LuminanceAlpha, false);
In the procedure render()
public void render() {
mapRenderer.render();
batch.begin();
batch.draw(pixmapTexture, 0, 0);
batch.end();
}
If I use Format. Alpha when creating the Pixmap and Texture, I neither see the more translucent circle.
Here is my problem:
Problem
Could somebody help me? What should I do, what should I init before to draw a full transparent circle? Thanks.
UPDATE
I have found the answer for my problem. I have to disable blending to avoid the problem.
Now my code:
FrameBuffer fbo = new FrameBuffer(Format.RGBA8888, 620, 620, false);
Texture tex = EnemyOnRadar.assetManager.get("data/sugar.png", Texture.class);
batch.begin();
// others
batch.end();
fbo.begin();
batch.setColor(1,1,1,0.7f);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
batch.begin();
batch.draw( tex, 100, 100);
batch.end();
fbo.end();
But I don't see the circle (it's a png image, represents transparent bg, white filled circle).

I am not sure if this works for you but i just share it:
You could use FrameBuffers and do the following:
Draw everything you want to draw on screen.
End your SpriteBatch and begin your FrameBuffer, begin the SpriteBatch again.
Draw the Fog, which fills the whole "screen" (FrameBuffer) with a black, non transparent color.
Draw the "Fogless" circle as a white circle, at the position you want to delete the fog.
Set the FrameBuffers alpha channel (transparancy) to 0.7 or something like that.
End the SpriteBatch and the FrameBuffer to draw it to screen.
What happens? You draw the normal scene, without fog. You create a "virtual screen", fill it with black and overdraw the black with a white circle. Now you set a transparacy to this "virtual screen" and overdraw your real screen with it. The part of the screen, which is under the white circle seems to be bright, while the black rest makes your scene darker.
Something to read: 2D Fire effect with libgdx, more or less the same as fog.
My question to this: Libgdx lighting without box2d
EDIT: another Tutorial.
Let me know if it helps!
EDIT: Some Pseudocode:
In create:
fbo = new FrameBuffer(Format.RGBA8888, width, height, false);
In render:
fbo.begin();
glClearColor(0f, 0f, 0f, 1f); // Set the clear color to black, non transparent
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); // Clear the "virtual screen" with the clear color
spriteBatch.begin(); // Start the SpriteBatch
// Draw the filled circles somehow // Draw your Circle Texture as a white, not transparent Texture
spriteBatch.end(); // End the spritebatch
fbo.end(); // End the FrameBuffer
spriteBatch.begin(); // start the spriteBatch, which now draws to the real screen
// draw your textures, sprites, whatever
spriteBatch.setColor(1f, 1f, 1f, 0.7f); // Sets a global alpha to the SpriteBatch, maybe it applies alo to the stuff you have allready drawn. If so just call spriteBatch.end() before and than spriteBatch.begin() again.
spriteBatch.draw(fbo, 0, 0); // draws the FBO to the screen.
spriteBatch.end();
tell me if it works

How to translate the camera in GLES2.0?

I want to create a camera moving above a tiled plane. The camera is supposed to move in the XY-plane only and to look straight down all the time. With an orthogonal projection I expect a pseudo-2D renderer.
My problem is, that I don't know how to translate the camera. After some research it seems to me, that there is nothing like a "camera" in OpenGL and I have to translate the whole world. Changing the eye-position and view center coordinates in the Matrix.setLookAtM-function just leads to distorted results.
Translating the whole MVP-Matrix does not work either.
I'm running out of ideas now; do I have to translate every single vertex every frame directly in the vertex buffer? That does not seem plausible to me.
I derived GLSurfaceView and implemented the following functions to setup and update the scene:
public void onSurfaceChanged(GL10 unused, int width, int height) {
GLES20.glViewport(0, 0, width, height);
float ratio = (float) width / height;
// Setup the projection Matrix for an orthogonal view
Matrix.orthoM(mProjMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
}
public void onDrawFrame(GL10 unused) {
// Draw background color
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
//Setup the camera
float[] camPos = { 0.0f, 0.0f, -3.0f }; //no matter what else I put in here the camera seems to point
float[] lookAt = { 0.0f, 0.0f, 0.0f }; // to the coordinate center and distorts the square
// Set the camera position (View matrix)
Matrix.setLookAtM( vMatrix, 0, camPos[0], camPos[1], camPos[2], lookAt[0], lookAt[1], lookAt[2], 0f, 1f, 0f);
// Calculate the projection and view transformation
Matrix.multiplyMM( mMVPMatrix, 0, projMatrix, 0, vMatrix, 0);
//rotate the viewport
Matrix.setRotateM(mRotationMatrix, 0, getRotationAngle(), 0, 0, -1.0f);
Matrix.multiplyMM(mMVPMatrix, 0, mRotationMatrix, 0, mMVPMatrix, 0);
//I also tried to translate the viewport here
// (and several other places), but I could not find any solution
//draw the plane (actually a simple square right now)
mPlane.draw(mMVPMatrix);
}

Changing the eye-position and view center coordinates in the "LookAt"-function just leads to distorted results.
If you got this from the android tutorial, I think they have a bug in their code. (made a comment about it here)
Try the following fixes:
Use setLookatM to point to where you want the camera to be.
In the shader, change the gl_Position line
from: " gl_Position = vPosition * uMVPMatrix;"
to: " gl_Position = uMVPMatrix * vPosition;"
I'd think the //rotate the viewport section should be removed as well, as this is not rotating the camera properly. You can change the camera's orientation in the setlookat function.

Rotate Image Clockwise using LibGDX

How can we rotate a Image Clockwise using LibGDX? what i am looking is when a image is loaded,suppose a star, i need to rotate it from beginning of screen to end of the screen horizontally, with star rotating,how can i do that in libgdx?

When you draw the Texture with your SpriteBatch, you can use one of the draw functions that includes rotation. This javadoc has all the draw functions: SpriteBatch
You can keep a variable for position and rotation, and increase the rotation and x component of the position each time you render to make it rotate while moving horizontally.

Libgdx gives you more then one way to do that:
You can use Scene2D and add an Image to your Stage. Image is a subclass of Actor, so you can add Actions to it:
Image myImage = new Image(myTexture);
myImage.addAction(Actions.parallel(Actions.moveTo(endX, endY, duration), Actions.rotateBy(degrees, duration)));
myImage.setPosition(startX, startY);
myImage.setOrigin(sizeX/2, sizeY/2);
stage.add(myImage);
In render you can then call stage.act(), which updates the position, rotation, scale... of all your Actors and then call stage.draw() which will call draw() for all your Actors.
Image allready handles the draw() so you don't need to care about that anymore.
You can also do it without scene2d, by updating everything yourself:
You can store a int rotationSpeed in degrees/sec
You can store a int moveSpeed in units/sec (maybe pixel but i would suggest to use camera or viewport and use your own unit, which is equal on all devices)
Store the float angle, which is the current rotation of your Texture
and store a Vector2 position, which contains the x and y position of your Texture.
If you want to move in x and y direction you can also store a Vector2 direction, which is a normalized Vector, giving the percent of movement in x and y direction, but thats a different story.
Then in your render(float delta) you update everything:
angle+=delta*rotationSpeed;
angl%=360; // Limits the angle to be <= 360
while (angle < 0) // Unfortunally the "modulo" in java gives negative result for negativ values.
angle+=360;
position.x+=direction.x*moveSpeed*delta;
position.y+=direction.y*movSpeed*delta;
spriteBatch.draw(yourTextureRegion, position.x, position.y, sizeX/2, sizeY/2, sizeX, sizeY, scaleX, scaleY, angle);
For clockwise rotation simply use a negative rotationSpeed or replace the angle+= with angle-=.
Hope it helps.

Following is the implementation to rotate any sprite
batch.draw(sprite,(Gdx.graphics.getWidth() - sprite.getRegionWidth()) / 2.0f,(Gdx.graphics.getHeight() - sprite.getRegionHeight()) / 2.0f,sprite.getRegionWidth()/2.0f,sprite.getRegionHeight()/2.0f, sprite.getRegionWidth(), sprite.getRegionHeight(), 1f, 1f,count, false);
if(count < 0.0f)
count = 360.0f;
else
count --;
Initially set counter to
private float count =360.0f;

You can also use the Scene2D actions. I have an example here with asteroid-type thing falling down the screen and rotating.
http://www.netthreads.co.uk/2012/02/09/libgdx-scene2d-demo-with-scene-transitions/

To rotate anticlockwise and horizontally..
create a textureRegion
then
Sprite sprite = new Sprite(textureRegion, 0, 0, 128, 128);
sprite.setPosition(++mX, 0);
angle++;
sprite.setRotation(angle);
sprite.draw(batcher);

You can do it too like this:
on your create method
sprite.setOrigin(sprite.getWitdh() /2f, sprite.getHeight() /2f);
sprite.setPosition( 0, 200 ); //200 it's a example
on your render(float delta)
sprite.setX( sprite.getX() + delta ).setRotation( sprite.getRotation() + delta );

Here is a simple to rotate an actor in libgdx. First you need to set the origin:
img.setOrigin(getWidth/2,getHeight/2);
And then you can rotate clockwise and anticlockwise according to your need:
img.rotate(2f); or img.rotate(-2f);

So the following sample worked for me (infinite rotation)
Method 1: (recommended)
loadingActor.addAction(Actions.repeat(RepeatAction.FOREVER, Actions.rotateBy(360, 1)));
Method 2:
Image loadingActor = new Image(AssetsController.getInstance().getLoading());
loadingActor.setOrigin(Align.center);
final SequenceAction infiniteRotate = Actions.sequence();
infiniteRotate.addAction(Actions.rotateTo(0 , 0f) );
infiniteRotate.addAction(Actions.rotateTo(360 , 1f) );
loadingActor.addAction(Actions.forever(infiniteRotate));