Issue while extending Fisica Fjoint class

aevol

Issue while extending Fisica Fjoint class

in Contributed Library Questions • 1 month ago

Hi there,

I would like to extend the Fjoint class of the Fisica library to make a new object I would call Flink.

Actually I just want it to draw a line when the distance between the two Fbody involved is less than the value of the m_vision field.

My problem is that nothing happens. It looks like the draw() method and the debugDraw method are not called.

I've done a lot of exploration of the code of the library and based my class extension to the FDistanceJoint class but I still cannot have any result.

The sketch work and there is no error or stack trace but I simply don't have my links !

Here is the class, ( nearly a copy of FDistanceJoint ) :

import processing.core.*;
import java.util.ArrayList;
import org.jbox2d.common.*;
import org.jbox2d.collision.*;
import org.jbox2d.collision.shapes.*;
import org.jbox2d.dynamics.*;
import org.jbox2d.dynamics.joints.*;
/////////////////////////////////////////////////////
public class aeFlink extends FJoint {
protected FBody m_body1;
protected FBody m_body2;
protected Vec2 m_anchor1;
protected Vec2 m_anchor2;
protected float m_vision;
/////////////////////////////////////////////////////
public aeFlink (FBody body1, FBody body2) {
super() ;
m_body1 = body1;
m_body2 = body2;
m_anchor1 = new Vec2(0.0f, 0.0f);
m_anchor2 = new Vec2(0.0f, 0.0f);
m_vision = 150;
}
////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////
public void draw(PGraphics applet) {
preDraw(applet);
println("test"); //->nothing print...
if (getDistance() < m_vision) {
applet.line(getAnchor1X(), getAnchor1Y(), getAnchor2X(), getAnchor2Y());
} //nothing draw...
postDraw(applet);
}
////////////////////////////////////////////////////////////////
public void drawDebug(PGraphics applet) {
preDrawDebug(applet);
applet.line(getAnchor1X(), getAnchor1Y(), getAnchor2X(), getAnchor2Y());
postDrawDebug(applet);
}
////////////////////////////////////////////////////////////////
public float getDistance() {
float lengthX = ((m_body1.getX() + getAnchor1X()) - (m_body2.getX() + getAnchor2X()));
float lengthY = ((m_body1.getY() + getAnchor1Y()) - (m_body2.getY() + getAnchor2Y()));
float distance = (float)Math.sqrt(lengthX*lengthX + lengthY*lengthY);
return distance;
}
////////////////////////////////////////////////////////////////
public float getAnchor1X() {
if (m_joint != null) {
return Fisica.worldToScreen(m_joint.getAnchor1()).x;
}
return Fisica.worldToScreen(m_anchor1.x);
}
////////////////////////////////////////////////////////////////
public float getAnchor1Y() {
if (m_joint != null) {
return Fisica.worldToScreen(m_joint.getAnchor1()).y;
}
return Fisica.worldToScreen(m_anchor1.y);
}
////////////////////////////////////////////////////////////////
public float getAnchor2X() {
if (m_joint != null) {
return Fisica.worldToScreen(m_joint.getAnchor2()).x;
}
return Fisica.worldToScreen(m_anchor2.x);
}
////////////////////////////////////////////////////////////////
public float getAnchor2Y() {
if (m_joint != null) {
return Fisica.worldToScreen(m_joint.getAnchor2()).y;
}
return Fisica.worldToScreen(m_anchor2.y);
}
////////////////////////////////////////////////////////////////
public void setAnchor2(float x, float y) {
if (m_joint != null) {
((DistanceJoint)m_joint).getAnchor2().set(Fisica.screenToWorld(x), Fisica.screenToWorld(y));
}
m_anchor2 = Fisica.screenToWorld(x, y);
}
////////////////////////////////////////////////////////////////
public void setAnchor1(float x, float y) {
if (m_joint != null) {
((DistanceJoint)m_joint).getAnchor1().set(Fisica.screenToWorld(x), Fisica.screenToWorld(y));
}
m_anchor1 = Fisica.screenToWorld(x, y);
}
////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////
//end class aeFlink
}

And this is the sketch to see how it is instantiated :

import fisica.*;
FWorld world;
FCircle[] balls;
aeFlink[] links;
int nombreDeBalles = 10;
float boundXL = 5;
float boundXR = 700-5;
float boundYT = 5;
float boundYB = 700-5;
color backColor = 40;
int radius = 22;
//////////////////////////////////////////////////////////
void setup() {
size(1000, 700);
smooth();
frameRate(60);
Fisica.init(this);
world = new FWorld();
world.setGravity(0, 0);
world.setEdges(boundXL, boundYT, boundXR, boundYB );
world.setEdgesRestitution(1);
world.setEdges(int(backColor));
balls = new FCircle[nombreDeBalles];
for (int i = 0; i<nombreDeBalles; i++) {
//int d = int(random (100, 200));
int d = 20;
balls[i] = new FCircle(radius);
balls[i].setPosition(random(100, 500), random(100, 500));
//balls[i].setVelocity(random(-200, 200), random(-200, 200));
balls[i].setDensity(1+d);
balls[i].setRestitution(1.0);
balls[i].setDamping(0.0001);
balls[i].setStroke(0);
balls[i].setStrokeWeight(1);
balls[i].setFill(235 - d);
//balls[i].setSensor(true);
balls[i].setFriction(0);
world.add(balls[i]);
}
links = new aeFlink[nombreDeBalles];
for (int i = 0; i<nombreDeBalles; i++) {
links[i] = new aeFlink(balls[i], balls[(i+1)%nombreDeBalles]);
links[i].setStroke(255);
links[i].setStrokeWeight(1);
links[i].setCollideConnected(true);
links[i].setDrawable(true);
world.add(links[i]);
}
//end setup
}
//////////////////////////////////////////////////////////
void draw() {
background(backColor);
world.draw();
world.step();
noFill();
stroke(255);
rect(boundXL+4, boundYT+4, boundXR-boundXL-8, boundXR-boundXL-8, 5);
//end draw
}

So.... any idea ?

Replies(3)

GoToLoop

Re: Issue while extending Fisica Fjoint class

1 month ago

I'm just risking a guess:

Fisica library is a package. And it seems like they all depend to each other.

Even though your class aeFlink extends FJoint, the rest of the package, like FWorld and FCircle for example,
will keep on using the original FJoint; not your "hacked" custom class!

Perhaps only those classes which have extends FJoint in their definition won't be using yours.

I guess you'd have to replace FJoint w/ your own modified class within that library itself!
Either that or overriding every1!

aevol

Re: Issue while extending Fisica Fjoint class

1 month ago

Hum, I was afraid it was something like this.

The FWorld instance probably doesn't see my links.

As the Fjoint class is abstract maybe I could just write my extending class in a ".java" file and put it in the /code folder of my sketch with the " package Fisica ; " statement?

It's not quite clear, I'm still juggling with all this "abstract static public private protected" stuff...

Thank you for this quick answer !

GoToLoop

Re: Issue while extending Fisica Fjoint class

1 month ago

As the Fjoint class is abstract maybe I could just write my extending class in a ".java" file and put it in the /code folder of my sketch with the " package Fisica ; " statement?

I don't think being abstract or an interface has anything to do with that.
Classes which extend or implement some class or interface "name", will always use that very same "name".
Creating another class extending that "name" won't force the other classes to use that modified version
with a different name!

Perhaps the idea of creating a .java file w/ the same name as the class you wanna hack is the right path.
Below I've hacked the PVector class to do nothing useful. It's completely overridden the original PVector!

"test.pde":

void setup() {
  PVector q = new PVector(10, 30);
  exit();
}

"PVector.java":

class PVector {
  PVector(int xx, int yy) {
    System.out.println(xx + yy*xx);
  }
}

Who knows you can do the same to the FJoint class.

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