Interaction between "blobs" with Box2D

helloauan

Interaction between "blobs" with Box2D

in Contributed Library Questions • 2 years ago

Hey all,

I am happily playing around and trying to further the " blob" example from Daniel Shiffman's Box2d library for Processing.

What I am trying to do is create two blobs that can interact(collide) with each other. I am able to easily create two different blob objects yet they seem to render on different layers and are not influenced by each other.

My two objects:

import pbox2d.*;
import org.jbox2d.collision.shapes.*;
import org.jbox2d.common.*;
import org.jbox2d.dynamics.*;
import org.jbox2d.dynamics.joints.*;
// A reference to our box2d world
PBox2D box2d;
// A list we'll use to track fixed objects
ArrayList<Boundary> boundaries;
// Our "blob" objects
Blob blob;
Blob blob2;
void setup() {
size(400,300);
smooth();
// Initialize box2d physics and create the world
box2d = new PBox2D(this);
box2d.createWorld();
// Add some boundaries
boundaries = new ArrayList<Boundary>();
boundaries.add(new Boundary(width/2,height-5,width,10));
boundaries.add(new Boundary(width/2,5,width,10));
boundaries.add(new Boundary(width-5,height/2,10,height));
boundaries.add(new Boundary(5,height/2,10,height));
// Make new blobs
blob = new Blob();
blob2 = new Blob();
}
void draw() {
background(255);
// We must always step through time!
box2d.step();
// Show the blobs!
blob.display();
blob2.display();
// Show the boundaries!
for (Boundary wall: boundaries) {
wall.display();
}
// Here we create a dynamic gravity vector based on the location of our mouse
PVector g = new PVector(mouseX-width/2,mouseY-height/2);
g.normalize();
g.mult(10);
}

Blob class:

// The Nature of Code
// <http://www.shiffman.net/teaching/nature>
// Spring 2010
// PBox2D example
// A blob skeleton
// Could be used to create blobbly characters a la Nokia Friends
// http://postspectacular.com/work/nokia/friends/start
class Blob {
// A list to keep track of all the points in our blob
ArrayList<Body> skeleton;
float bodyRadius; // The radius of each body that makes up the skeleton
float radius; // The radius of the entire blob
float totalPoints; // How many points make up the blob
// We should modify this constructor to receive arguments
// So that we can make many different types of blobs
Blob() {
// Create the empty
skeleton = new ArrayList<Body>();
// Let's make a volume of joints!
ConstantVolumeJointDef cvjd = new ConstantVolumeJointDef();
// Where and how big is the blob
Vec2 center = new Vec2(random(100,width-100),random(100,height/2));
radius = random(30,60);
totalPoints = 40;
bodyRadius = 1;
// Initialize all the points
for (int i = 0; i < totalPoints; i++) {
// Look polar to cartesian coordinate transformation!
float theta = PApplet.map(i, 0, totalPoints, 0, TWO_PI);
float x = center.x + radius * sin(theta);
float y = center.y + radius * cos(theta);
// Make each individual body
BodyDef bd = new BodyDef();
bd.fixedRotation = true; // no rotation!
bd.position.set(box2d.coordPixelsToWorld(x,y));
Body body = box2d.createBody(bd);
// The body is a circle
CircleDef cd = new CircleDef();
cd.radius = box2d.scalarPixelsToWorld(bodyRadius);
cd.density = 1.0f;
// For filtering out collisions
cd.filter.groupIndex = -2;
// Finalize the body
body.createShape(cd);
// Add it to the volume
cvjd.addBody(body);
// We always do this at the end
body.setMassFromShapes();
// Store our own copy for later rendering
skeleton.add(body);
}
// These parameters control how stiff vs. jiggly the blob is
cvjd.frequencyHz = 12.0f;
cvjd.dampingRatio = 2.0f;
// Put the joint thing in our world!
box2d.world.createJoint(cvjd);
}
// Time to draw the blob!
// Can you make it a cute character, a la http://postspectacular.com/work/nokia/friends/start
void display() {
// Draw the outline
beginShape();
fill(150);
noStroke();
strokeWeight(1);
for (Body b: skeleton) {
Vec2 pos = box2d.getBodyPixelCoord(b);
vertex(pos.x,pos.y);
}
endShape(CLOSE);
// Draw the individual circles
/*for (Body b: skeleton) {
// We look at each body and get its screen position
Vec2 pos = box2d.getBodyPixelCoord(b);
// Get its angle of rotation
float a = b.getAngle();
pushMatrix();
translate(pos.x,pos.y);
rotate(a);
fill(175);
stroke(0);
strokeWeight(1);
ellipse(0,0,bodyRadius*2,bodyRadius*2);
popMatrix();
}*/
}

Boundary class:

http://www.shiffman.net/itp/classes/nature/box2d_2010/blob/Boundary.pde

I know it's probably right under my nose, yet if I could get some advice I'd really appreciate it!

Thanks

Interaction between "blobs" with Box2D

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