Develop Reference

libgdx - find the coordinates different from the point of origin?

I 'd like someone to advise me a way to find the coordinates of a point on a sprite in libgdx .
As you can see from the image I have set the sprite with the point of origin on the red dot , and I can not change it.
I would leave the red dot as the source and find the coordinates of the green on the same sprite .
Thanks for your help.
EDIT
#Override
public void create () {
img = new Texture("rocket.png");
font = new BitmapFont();
font.setColor(Color.BLUE);
MyInputProcessor inputProcessor = new MyInputProcessor();
Gdx.input.setInputProcessor(inputProcessor);
float w = Gdx.graphics.getWidth();
float h = Gdx.graphics.getHeight();
sprite = new Sprite(img);
spacesprite = new Sprite(new Texture(Gdx.files.internal("space.jpg")));
spacesprite.setPosition(0,0);
spacesprite.setSize(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
point = new Sprite(new Texture(Gdx.files.internal("point.png")));
batch = new SpriteBatch();
}
#Override
public void render () {
sprite.setPosition(Gdx.graphics.getWidth() / 2 - sprite.getWidth()/2, Gdx.graphics.getHeight() / 2 - sprite.getHeight()/2);
sprite.setOrigin(sprite.getWidth()/2, sprite.getHeight()/2);
point.setPosition(sprite.getX() + sprite.getWidth()/2 - point.getWidth()/2, sprite.getY() + sprite.getHeight()/2);
point.setOrigin(point.getWidth()/2, 0);
if(Gdx.input.isButtonPressed(Input.Buttons.LEFT)){
//sprite.setPosition(Gdx.input.getX() - sprite.getWidth()/2, Gdx.graphics.getHeight() - Gdx.input.getY() - sprite.getHeight()/2);
if(Gdx.input.getX() < Gdx.graphics.getWidth() / 2)
{
//System.out.println("x: " + Gdx.input.getX() + " - y: " + Gdx.input.getY());
sprite.setRotation(rotation++);
point.setRotation(rotation++);
System.out.println("Sprite: X" + sprite.getX() + " - Y:" + sprite.getY());
}
else
{
//System.out.println("x: " + Gdx.input.getX() + " - y: " + Gdx.input.getY());
sprite.setRotation(rotation--);
point.setRotation(rotation--);
System.out.println("Sprite: X" + sprite.getX() + " - Y:" + sprite.getY());
}
}
batch.begin();
spacesprite.draw(batch);
sprite.draw(batch);
point.draw(batch);
batch.end();
}
someone can adapt the code , when I rotate I'd get the position , but they are insecure about my implementation .

if you're looking for a middle point on the rectangular sprite, try something like this:
float x = obj.getOriginX() + obj.getHeight();
float y = obj.getOriginY() + obj.getWidth() / 2;

Either use Gonio, matrix or quaternions to calculate the rotated coordinates.
For a few simple calculations I'd use gonio, something like:
float angle_rad = sprite.getRotation() / 180.0f * PI;
float rotated_x = Math.sin(angle_rad) * y + Math.cos(angle_rad) * x;
float rotated_y = Math.sin(angle_rad) * x + Math.cos(angle_rad) * y;
If you have to do this more often look into matrices or quaternions, matrices are a little easier though: http://en.wikipedia.org/wiki/Rotation_matrix

Getting the overlapping area of two circles

I'm in a tremendous bind with a last minute request on a consulting project I'm working on.
Essentially here is what I am trying to accomplish:
I have a surfaceview that draws a series of randomly sized circles. Each circle can have a radius from 50-100.
The x,y values are randomly generated along with a random radius
Each circle is created as an object representing that circle (x, y coord's and radius) and it is added to a list.
Once they are all created they are drawn.
The problem is I want to make sure none of these circles overlap.
I'm struggling a bit. This seems like it's shouldn't be all that difficult but it is for me unfortunately.
Here's my code so far (I know it's not close...be kind):
x = 100 + (int) (Math.random() * (mCanvasWidth - 200));
y = 100 + (int) (Math.random() * (mCanvasHeight - 200));
radius = 50 + (int) (Math.random() * 99);
color[0] = (float) (Math.random() * 360);
color[1] = 1;
color[2] = 1;
String radVal = String.valueOf(radius);
circle circ = new circle(x, y, radius, Color.HSVToColor(128, color), radVal);
boolean addit = true;
for (dot d : Dots) {
int leftSide = d.get_x() - radius;
int rightSide = d.get_x() + radius;
int xBoundary = x + radius;
int yBoundary = y + radius;
int exist_xLeft = d.get_x() - d.get_radius();
int exist_xRight = d.get_x() + d.get_radius();
int exist_yTop = d.get_y() - d.get_radius();
int exist_yBottom = d.get_y() + d.get_radius();
if ((xBoundary > exist_xLeft) && (xBoundary < exist_xRight))
{
if (yBoundary > (exist_yTop) && (yBoundary < exist_yBottom)) {
addit = false;
break;
}
}
}
if (addit)
circles.add(mdot);
if (circles.size() >= 5)
running = false;
Then it iterates the circles list and draws them to the canvas.
Any suggestions on where I'm failing in the collision detection?

You can detect if 2 circles are colliding like this:
Given:
centerpoints cx1,cy1 & cx2,cy2
and given radii r1 & r2,
Then you can determine if the 2 circles are colliding:
areColliding=((cx2-cx1)*(cx2-cx1)+(cy2-cy1)*(cy2-cy1))<((r1+r2)*(r1+r2));

Android Canvas: Get Y position of drawn line in canvas [duplicate]

I'd like to calculate a point on a quadratic curve. To use it with the canvas element of HTML5.
When I use the quadraticCurveTo() function in JavaScript, I have a source point, a target point and a control point.
How can I calculate a point on the created quadratic curve at let's say t=0.5 with "only" knowing this three points?

Use the quadratic Bézier formula, found, for instance, on the Wikipedia page for Bézier Curves:
In pseudo-code, that's
t = 0.5; // given example value
x = (1 - t) * (1 - t) * p[0].x + 2 * (1 - t) * t * p[1].x + t * t * p[2].x;
y = (1 - t) * (1 - t) * p[0].y + 2 * (1 - t) * t * p[1].y + t * t * p[2].y;
p[0] is the start point, p[1] is the control point, and p[2] is the end point. t is the parameter, which goes from 0 to 1.

In case somebody needs the cubic form:
//B(t) = (1-t)**3 p0 + 3(1 - t)**2 t P1 + 3(1-t)t**2 P2 + t**3 P3
x = (1-t)*(1-t)*(1-t)*p0x + 3*(1-t)*(1-t)*t*p1x + 3*(1-t)*t*t*p2x + t*t*t*p3x;
y = (1-t)*(1-t)*(1-t)*p0y + 3*(1-t)*(1-t)*t*p1y + 3*(1-t)*t*t*p2y + t*t*t*p3y;

I created this demo :
// x = a * (1-t)³ + b * 3 * (1-t)²t + c * 3 * (1-t)t² + d * t³
//------------------------------------------------------------
// x = a - 3at + 3at² - at³
// + 3bt - 6bt² + 3bt³
// + 3ct² - 3ct³
// + dt³
//--------------------------------
// x = - at³ + 3bt³ - 3ct³ + dt³
// + 3at² - 6bt² + 3ct²
// - 3at + 3bt
// + a
//--------------------------------
// 0 = t³ (-a+3b-3c+d) + => A
// t² (3a-6b+3c) + => B
// t (-3a+3b) + => c
// a - x => D
//--------------------------------
var A = d - 3*c + 3*b - a,
B = 3*c - 6*b + 3*a,
C = 3*b - 3*a,
D = a-x;
// So we need to solve At³ + Bt² + Ct + D = 0
Full example here
may help someone.

I edited talkhabis answer (cubic curve) so the curve is displayed with the right coordinates. (Couldn't comment)
The Y-coordinates needed to be changed (-p[].y+150). (A new variable for that might be a nicer and more efficient solution, but you get the idea)
// Apply points to SVG and create the curve and controllers :
var path = document.getElementById('path'),
ctrl1 = document.getElementById('ctrl1'),
ctrl2 = document.getElementById('ctrl2'),
D = 'M ' + p0.x + ' ' + (-p0.y+150) +
'C ' + c0.x + ' ' + (-c0.y+150) +', ' + c1.x + ' ' + (-c1.y+150) + ', ' + p1.x + ' ' + (-p1.y+150);
path.setAttribute('d',D);
ctrl1.setAttribute('d','M'+p0.x+','+(-p0.y+150)+'L'+c0.x+','+(-c0.y+150));
ctrl2.setAttribute('d','M'+p1.x+','+(-p1.y+150)+'L'+c1.x+','+(-c1.y+150));
// Lets test the "Bezier Function"
var t = 0, point = document.getElementById('point');
setInterval(function(){
var p = Bezier(p0,c0,c1,p1,t);
point.setAttribute('cx',p.x);
point.setAttribute('cy',-p.y+150);
t += 0.01;
if(t>=1) t=0;
},50);
// OK ... Now tring to get "y" on cruve based on mouse "x" :
var svg = document.getElementById('svg'),
point2 = document.getElementById('point2');
svg.onmousemove = function(e){
var x = (e.pageX - 50)/2,
y = (e.pageY - 50)/2;
// "-50" because of "50px margin" on the left side
// and "/2" because the svg width is 300 units and 600 px => 300 = 600/2
// Get the x,y by mouse x
var p = YBX(p0,c0,c1,p1,x);
point2.setAttribute('cx',p.x);
point2.setAttribute('cy',-p.y+150);
}
http://jsfiddle.net/u214gco8/1/
I also created some C-Code to test the results for the cubic curve. Just enter the X and Y coordinates in the main function.
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
void bezierCurve(int x[] , int y[])
{
double xu = 0.0 , yu = 0.0 , u = 0.0 ;
int i = 0 ;
for(u = 0.0 ; u <= 1.0 ; u += 0.05)
{
xu = pow(1-u,3)*x[0]+3*u*pow(1-u,2)*x[1]+3*pow(u,2)*(1-u)*x[2]
+pow(u,3)*x[3];
yu = pow(1-u,3)*y[0]+3*u*pow(1-u,2)*y[1]+3*pow(u,2)*(1-u)*y[2]
+pow(u,3)*y[3];
printf("X: %i Y: %i \n" , (int)xu , (int)yu) ;
}
}
int main(void) {
int x[] = {0,75,50,300};
int y[] = {0,2,140,100};
bezierCurve(x,y);
return 0;
}
https://ideone.com/glLXcB

Just a note: If you are using the usual formulas presented here then don't expect t = 0.5 to return the point at half of the curve's length.. In most cases it won't.
More on this here under "§23 — Tracing a curve at fixed distance intervals" and here.

Is there a method that checks if an libgdx Scene2d Image or Actor is touched?

here's my sample from the libgdx android game that I want to create. Nothing special yet, cause I'm just starting my adventure with Android games.
Here is a couple of questions I would like to get answered
So far I am using the Gdx.input.isTouched function and check if that matches the bunny coordinates, I do that for each bunny and at the end I would like to have 11 of them and that's just too much to write. Is there a way to check if the Image class from import com.badlogic.gdx.scenes.scene2d.ui.Image; was touched? Or else does the Actor class has that feature?
Another thing is that when I instantiate the bunny class and I click the bunny, all of them are changing to "scared". It's because the Scene2d.Image texture has to be static. Is there a way to change that?
if(Gdx.input.isTouched()){
x = Gdx.input.getX();
y = Gdx.graphics.getHeight() - Gdx.input.getY();
// **** Show Coordinates **** \\
if (x < 420)
font.draw(batch, "x:" + x +
"\n y: " + y, x, y);
else
font.draw(batch, "x:" + x +
" y: " + y, x-65, y);
// **** End Show Coordinates **** \\
//if krolik (bunny) is touched add highscore and change texture to scared
if (x >= krolik.pos.x && y >= krolik.pos.y
&& x <= krolik.pos.x + 64 && y <= krolik.pos.y + 64)
{
krolik.scared();
highscore+=100;
}
else if (x >= krolik2.pos.x && y >= krolik2.pos.y
&& x <= krolik2.pos.x + 64 && y <= krolik2.pos.y + 64)
{
krolik2.scared();
highscore+=100;
}
}
else{
krolik.normal();
}
// **** Show Highscore **** \\
font.draw(batch, "Highscore: " + highscore, 350, 300);
batch.draw(krolik.getTexture(), krolik.pos.x, krolik.pos.y);
batch.draw(krolik2.getTexture(), krolik2.pos.x, krolik2.pos.y);
batch.end();

Why is it that you are using Image but not drawing with Stage? Image and other Actors are for using Stage which can take care of your touch events and drawing very easily.
Create them like this:
for (int i = 0; i < KROLIKS_COUNT; i++) {
final Image krolik = new Image(nonScaredTextureRegion);
krolik.setClickListener(new ClickListener() {
#Override
public void click(Actor actor, float x, float y) {
krolik.setRegion(scaredTextureRegion);
highscore+=100;
}
});
krolik.x = startPosX;
krolik.y = startPosY;
stage.addActor(krolik);
}
set the stage as the input processor:
Gdx.input.setInputProcessor(stage);
then in render, simply:
stage.act(Gdx.graphics.getDeltaTime());
stage.draw();

Retrieve the X & Y coordinates of a button in android?

I've been working on Android for a while and would like to know if it is possible to retrieve the position of a button in android.
My target is to get the X & Y coordinates and print them on the LOGCAT.
Some example to show me how would be appreciated.
Thanks

Sure, you can get these, make sure the views are drawn atleast once before you try to get the positions. You could try to get the positions in onResume() and try these functions
view.getLocationInWindow()
or
view.getLocationOnScreen()
or if you need something relative to the parent, use
view.getLeft(), view.getTop()
Links to API definitions:
getLocationInWindow
getLocationOnScreen
getLeft
getTop

Like Azlam said you can use View.getLocationInWindow() to get the coordinates x,y.
Here is an example:
Button button = (Button) findViewById(R.id.yourButtonId);
Point point = getPointOfView(button);
Log.d(TAG, "view point x,y (" + point.x + ", " + point.y + ")");
private Point getPointOfView(View view) {
int[] location = new int[2];
view.getLocationInWindow(location);
return new Point(location[0], location[1]);
}
Bonus - To get the center point of the given view:
Point centerPoint = getCenterPointOfView(button);
Log.d(TAG, "view center point x,y (" + centerPoint.x + ", " + centerPoint.y + ")");
private Point getCenterPointOfView(View view) {
int[] location = new int[2];
view.getLocationInWindow(location);
int x = location[0] + view.getWidth() / 2;
int y = location[1] + view.getHeight() / 2;
return new Point(x, y);
}
I hope the example can still be useful to someone.

buttonObj.getX();
buttonObj.getY();