Here is a snippet of code that I have. I am trying to bound my object in a circle rather than a square, but there are things wrong with my code that I can't figure out. I have both the rectangle bounds which work and the circle bounds which don't work.
// get the pos
_touchingPoint.x = (int)event.getX();
_touchingPoint.y = (int)event.getY();
angle = Math.atan2(_touchingPoint.y , _touchingPoint.x);
// bound to a box
if( _touchingPoint.x < 75){
_touchingPoint.x = 75;
}
if ( _touchingPoint.x > 225){
_touchingPoint.x = 225;
}
if (_touchingPoint.y < 300){
_touchingPoint.y = 300;
}
if ( _touchingPoint.y > 450 ){
_touchingPoint.y = 450;
}
//bound to a circle
if( _touchingPoint.x < 75 * Math.cos(angle))
{
_touchingPoint.x = (int) (75 * Math.cos(angle));
}
if ( _touchingPoint.x > 225 * Math.cos(angle))
{
_touchingPoint.x = (int) (225 * Math.cos(angle));
}
if ( _touchingPoint.y < 300 * Math.sin(angle))
{
_touchingPoint.y = (int) (300 * Math.sin(angle));
}
if ( _touchingPoint.y > 450 * Math.sin(angle))
{
_touchingPoint.y = (int) (450 * Math.sin(angle));
}
_touchingPoint.x and _touchingPoint.y represent the object (Joystick) that I am trying to constrain. I figured I could try simple trig to constrain the Joystick to a circle, but I guess I was wrong.
What would be the best way to set up a circle constraint?
You seem to be trying to constrain the position to a circular disk, not a circle which is its boundary. I'd accomplish this by rescaling the offset vector from the center:
double dx = event.getX() - 150;
double dy = event.getY() - 375;
double len = Math.hypot(dx, dy);
if (len > 75) {
dx = dx*75/len;
dy = dy*75/len;
}
_touchingPoint.x = (int)dx + 150;
_touchingPoint.y = (int)dy + 375;
The code appears to have calculated the angle of your point from (0,0) then bounding it based on comparing its x with some function of that angle. For example, 75 * Math.cos(angle) varies between -75 and +75, whereas you want to be comparing the point with centre of a circle.
Set up variables for the centre of the circle (cx and cy) and the difference in the x and y ordinates (dx and dy).
You then want to test whether the distance from the centre exceeds your desired radius (usually this is done with the square of the distance as it avoids a sqrt operation - dx*dx+dy*dy>r*r).
If the distance is greater than the radius, project back to the circle, either using trig or by scaling the difference :
double dx = event.getX() - cx;
double dy = event.getY() - cy;
double d2 = dx*dx+dy*dy;
if(d2>r*r) {
double scale = r / Math.sqrt(d2);
dx*=scale;
dy*=scale;
}
then ( dx + cx, dy + cy ) will lie within the circle defined by cx,cy and r.
Unless I'm missing something, it would be along these lines:
===EDIT=== ONE THING I was missing, as pointed out by Pete, was how angle should be computed:
angle = atan2(y - 375, x - 150);
=== end of edit ===
a = _touchingPoint.x;
b = _touchingPoint.y;
if((a-150)*(a-150) + (b-375)*(b-375) > 75*75){
_touchingPoint.x = 150 + 75*cos(angle);
_touchingPoint.y = 375 + 75*sin(angle);
}
Related
I want my player rotate towards mouse. Here's the code calculating the angle:
float angle = (float) Math.atan2(MouseInput.getMousePos().y - transform.position.y + transform.size.y / 2,
MouseInput.getMousePos().x - transform.position.x + transform.size.x / 2);
angle = (float) (angle * (180 / Math.PI));
if (angle < 0) {
angle = 360 + angle;
}
transform.rotation = 180 + angle;
And getMousePos() method (it just returns mouse pos relative to window):
public static Vector2 getMousePos() {
Point p = MouseInfo.getPointerInfo().getLocation();
return new Vector2(p.x - Game.w.getAccessToWindow(Acces.WINDOW_JFRAME_ACCES).getLocation().x,
p.y - Game.w.getAccessToWindow(Acces.WINDOW_JFRAME_ACCES).getLocation().y);
}
Can you tell me what's wrong with this code? Player isn't rotating properly.
I tried following this article: https://gamefromscratch.com/gamedev-math-recipes-rotating-to-face-a-point/
Update:
I found this post: Java 2d rotation in direction mouse point
Now I've updated my code to this:
int centerX = (int) (transform.size.x / 2);
int centerY = (int) (transform.size.x / 2);
int mouseX = (int) MouseInput.getMousePos().x;
int mouseY = (int) MouseInput.getMousePos().y;
double angle = Math.atan2(centerY - mouseY, centerX - mouseX) - Math.PI / 2;
transform.rotation = angle;
But still something is off. Try this code for yourself. Maybe I did something wrong somewhere else.
I am trying to make a simple game where you basically have to hit the circles to get a point. But i faced a tiny problem which i couldn't really solve on my own so here is my question how do I repaint a round surface.I used the repaint(Rectangle r) method but it doesn't workout.
public void objectHit(MouseEvent e) {
int distance = 0, deltaX = 0, deltaY = 0, RadiusSqaured = 0;
for (int i = 0; i < obj.length; i++) {
deltaX = e.getX() - obj[i].getPoint().x;
deltaY = e.getY() - obj[i].getPoint().y;
distance = deltaX * deltaX + deltaY * deltaY;
RadiusSqaured = obj[i].getRadius() * obj[i].getRadius();
if (distance <= RadiusSqaured) {
repaint(obj[i].repaintRect());
x = ThreadLocalRandom.current().nextInt(50 + radius / 2, 850 - radius / 2);
y = ThreadLocalRandom.current().nextInt(60 + radius / 2, 750 - radius / 2);
repaint(obj[i].repaintRect());
}
}
}
In JComponent, there is a method for repainting based on a box area. Does this satisfy your requirements?
https://docs.oracle.com/javase/8/docs/api/javax/swing/JComponent.html#repaint-long-int-int-int-int-
I am going to try my best to give context for the below code. This is a method used to draw a circle and its center point in a 50x50 white square background. The following variables were used:
xc,yx - the center coordinates used to compute the circle
r - the radius of the circle
STEP - how often a new point is drawn on the circumference of the circle
x,y - the coordinates of each point that will make up the circle
Right now, my method uses a for loop to compute each points R,G, and B coordinates along the circumference of the circle based on the center point and the radius. What I am trying to do is anti-alias my output circle so that the round parts are not as jagged. However, I want to do this using only math and variables and I do not want to use any of Java's build in methods. Thank you to anyone who can help or point me in the right direction.
Below is my routine:
protected void proc_21() {
info = "Draw anti-aliased circle";
int xc = (int) rand(1, imgW - 2);
int yc = (int) rand(1, imgH - 2);
int r = (int) rand(4, 0.35f * (imgW + imgH));
int STEP = (2 * (int) Math.PI * r) * 57;
System.out.printf("circle centered at (%d,%d), radius = %d, draw in %d steps. \n", xc,yc,r,STEP);
for (int i = 0; i < STEP; i++) {
int x = (int) Math.round(xc + r * Math.cos(i));
int y = (int) Math.round(yc + r * Math.sin(i));
if (0 <= x && x < imgW) {
if ( 0 <= y && y < imgH) {
imgNew.setR(x, y, 0);
imgNew.setG(x, y, 0);
imgNew.setB(x, y, 1);
}
}
}
// set center to red
imgNew.setR(xc, yc, 1);
imgNew.setG(xc, yc, 0);
imgNew.setB(xc, yc, 0);
}
I have a large bulk of photographs taken with a fisheye lens. As I want to do some image-processing (e.g. edge detection) on the photos I want to remove the barrel distortion which effects my results heavily.
After some research and lots of read articles I found this page: They describe an algorithm (and some formulas) to solve this problem.
M = a *rcorr^3 + b * rcorr^2 + c * rcorr + d
rsrc = (a * rcorr^3 + b * rcorr^2 + c * rcorr + d) * rcorr
rsrc = distance of a pixel from the center of the source image
rcorr = distance of a pixel from the center in the corrected image
a,b,c = distortion of image
d = linear scaling of image
I used these formulas and tried to implement this in a Java application. Unfortunately it doesn't work and I failed to make it work. "Corrected" image look nothing like the original photograph and instead show some mysterious circles in the middle. Look here:
http://imageshack.us/f/844/barreldistortioncorrect.jpg/
(this used to be a photograph of a white cow in front a blue wall)
Here is my code:
protected int[] correction(int[] pixels) {
//
int[] pixelsCopy = pixels.clone();
// parameters for correction
double paramA = 0.0; // affects only the outermost pixels of the image
double paramB = -0.02; // most cases only require b optimization
double paramC = 0.0; // most uniform correction
double paramD = 1.0 - paramA - paramB - paramC; // describes the linear scaling of the image
//
for(int x = 0; x < dstView.getImgWidth(); x++) {
for(int y = 0; y < dstView.getImgHeight(); y++) {
int dstX = x;
int dstY = y;
// center of dst image
double centerX = (dstView.getImgWidth() - 1) / 2.0;
double centerY = (dstView.getImgHeight() - 1) / 2.0;
// difference between center and point
double diffX = centerX - dstX;
double diffY = centerY - dstY;
// distance or radius of dst image
double dstR = Math.sqrt(diffX * diffX + diffY * diffY);
// distance or radius of src image (with formula)
double srcR = (paramA * dstR * dstR * dstR + paramB * dstR * dstR + paramC * dstR + paramD) * dstR;
// comparing old and new distance to get factor
double factor = Math.abs(dstR / srcR);
// coordinates in source image
double srcXd = centerX + (diffX * factor);
double srcYd = centerY + (diffX * factor);
// no interpolation yet (just nearest point)
int srcX = (int)srcXd;
int srcY = (int)srcYd;
if(srcX >= 0 && srcY >= 0 && srcX < dstView.getImgWidth() && srcY < dstView.getImgHeight()) {
int dstPos = dstY * dstView.getImgWidth() + dstX;
pixels[dstPos] = pixelsCopy[srcY * dstView.getImgWidth() + srcX];
}
}
}
return pixels;
}
My questions are:
1) Is this formula correct?
2) Do I have made a mistake turning that formula into a piece of software?
3) There are other algorithms out there (e.g. How to simulate fisheye lens effect by openCV? or wiki/Distortion_(optics)), are they better?
Thanks for your help!
The main bug you have is that the algorithm specifies that r_corr and r_src are in units of min((xDim-1)/2, (yDim-1)/2). That needs to be done to normalise the calculation so that the parameter values are not dependent on the size of the source image. With the code as it is you'll need to use much smaller values for paramB, e.g. it worked ok for me with paramB = 0.00000002 (for an image with dimensions 2272 x 1704).
You also have a bug in calculating the difference from the center that causes the resulting image to be rotated 180 degree compared to the source image.
Fixing both these bugs should give you something like this:
protected static int[] correction2(int[] pixels, int width, int height) {
int[] pixelsCopy = pixels.clone();
// parameters for correction
double paramA = -0.007715; // affects only the outermost pixels of the image
double paramB = 0.026731; // most cases only require b optimization
double paramC = 0.0; // most uniform correction
double paramD = 1.0 - paramA - paramB - paramC; // describes the linear scaling of the image
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
int d = Math.min(width, height) / 2; // radius of the circle
// center of dst image
double centerX = (width - 1) / 2.0;
double centerY = (height - 1) / 2.0;
// cartesian coordinates of the destination point (relative to the centre of the image)
double deltaX = (x - centerX) / d;
double deltaY = (y - centerY) / d;
// distance or radius of dst image
double dstR = Math.sqrt(deltaX * deltaX + deltaY * deltaY);
// distance or radius of src image (with formula)
double srcR = (paramA * dstR * dstR * dstR + paramB * dstR * dstR + paramC * dstR + paramD) * dstR;
// comparing old and new distance to get factor
double factor = Math.abs(dstR / srcR);
// coordinates in source image
double srcXd = centerX + (deltaX * factor * d);
double srcYd = centerY + (deltaY * factor * d);
// no interpolation yet (just nearest point)
int srcX = (int) srcXd;
int srcY = (int) srcYd;
if (srcX >= 0 && srcY >= 0 && srcX < width && srcY < height) {
int dstPos = y * width + x;
pixels[dstPos] = pixelsCopy[srcY * width + srcX];
}
}
}
return pixels;
}
With this version you can use parameter values from existing lens databases like LensFun (though you'll need to flip the sign of each parameter). The page describing the algorithm can now be found at http://mipav.cit.nih.gov/pubwiki/index.php/Barrel_Distortion_Correction
I think your circles are caused by this line:
double srcYd = centerY + (diffX * factor);
which I'm guessing should be:
double srcYd = centerY + (diffY * factor);
Probably your radial distortion parameters are too large, and the image became packed on a sphere. Try to put smaller values in a,b,c and d.
Your values are very extreme, so you see extreme results.
Try a=0, b=0, c=1. That describes no correction at all, if your program is correct you should see the original image. Then gradually change c and b. Changing in increments of 0.1 is a good start.
I have a simple Java applet that has two user-controlled balls, drawn using java.awt. I need a way to detect a collision with between them. I have an algorithm for detecting collision with the walls:
if (xPosition > (300 - radius)){
xSpeed = -xSpeed;
}
else if (xPosition < radius){
xSpeed = -xSpeed;
}
else if (yPosition > (300 - radius)) {
ySpeed = -ySpeed;
}
else if (yPosition < radius){
ySpeed = -ySpeed;
}
xPosition += xSpeed;
yPosition += ySpeed;
and for the second ball:
if (xPosition2 > (300 - radius)){
xSpeed2 = -xSpeed2;
}
else if (xPosition2 < radius){
xSpeed2 = -xSpeed2;
}
else if (yPosition2 > (300 - radius)) {
ySpeed2 = -ySpeed2;
}
else if (yPosition2 < radius){
ySpeed2 = -ySpeed2;
}
xPosition2 += xSpeed2;
yPosition2 += ySpeed2;
The applet is 300 pixels by 300 pixels.
radius stores the radius of the circles.
xPosition and xPosition2 store the x coordinates for the two balls.
yPosition and yPosition store the y coordinates for the two balls,
xSpeed and xSpeed2 store the x velocities for the two balls.
ySpeed and ySpeed2 store the y velocities for the two balls.
Use http://java.sun.com/j2se/1.5.0/docs/api/java/awt/geom/Point2D.html, there's a distance method there, if it's less than the radius they're colliding.
EDIT:
Err, less than the radius * 2 , sorry
There's Point2D in Java or you can do it yourself, it is trivially easy for circle/circle collisions or sphere/sphere collisions.
int distXX = (xPosition1 - xPosition2) * (xPosition1 - xPosition2);
int distYY = (yPosition1 - yPosition2) * (yPosition1 - yPosition2);
if ( radius*radius > distXX * distYY ) {
... // There's a collision
}
public boolean colliding(Ball anotherBall) {
double xDelta = (this.x + this.ballSize/2 + this.dx) - (anotherBall.x + anotherBall.ballSize/2 + anotherBall.dx);
double YDelta = (this.y + this.ballSize/2 + this.dy) - (anotherBall.y + anotherBall.ballSize/2 + anotherBall.dy);
double distance = Math.sqrt(Math.pow(xDelta, 2) + Math.pow(YDelta, 2));
return (distance <= this.ballSize/2 + anotherBall.ballSize/2);
}
This Link is pretty useful!
Circle-Circle Collisions
It's very detailed and didatic
At the bottom of that page there are another links, to even more detailed stuff!
I used the Distance Between Centers method ---
Circles
By measuring the distance between each center you can say if they are colliding.
The distance should never be more then the sum of the 2 radius.
Here's what I did:
private boolean checkDrawContains(ShapeDrawable newHole)
{
long newCenterX = newHole.getBounds().left + (newHole.getBounds().width()/2); //Get the center of my shapes
long newCenterY = newHole.getBounds().top + (newHole.getBounds().height()/2);
for(ShapeDrawable hole: mHoles) // I was storing the circles in an ArrayList
{
long centerX = hole.getBounds().left + (hole.getBounds().width()/2); //Get the center of my shapes
long centerY = hole.getBounds().top + (hole.getBounds().height()/2);
long x = centerX - newCenterX;
long y = centerY - newCenterY;
long aux = (long) ((Math.pow(Math.abs(x),2)) + (Math.pow(Math.abs(y),2))); //Pythagoras the hard way :P
long distance = (long) Math.sqrt(aux);
long sRads = (newHole.getBounds().width()/2) + (hole.getBounds().width()/2);
if(distance <= sRads ) {
return true; //Is Colliding!
}
}
return false; // Is not Colliding!
}