Adding physics to a obj in processing - processing

Question

So I’m trying to give an obj some physics, and have work with the example of the bouncing ball that processing comes with, and I have make it instead of a ball to be a cylinder, but I can’t find the way to make the obj to have the physics.
I’m importing the obj with the library saito.objloader. I have this code, which is the invocation of the obj
import processing.opengl.*;
import saito.objloader.*;
OBJModel modelCan;
PVector location; // Location of shape
PVector velocity; // Velocity of shape
PVector gravity; // Gravity acts at the shape's acceleration
float rotX, rotY;
void setup() {
size(1028, 768, OPENGL);
frameRate(30);
modelCan = new OBJModel(this, "can.obj", "absolute", TRIANGLES);
modelCan.scale(50);
modelCan.translateToCenter();
modelCan.enableTexture();
location = new PVector(100,100,100);
velocity = new PVector(1.5,2.1,3);
gravity = new PVector(0,0.2,0);
}
void draw() {
background(129);
lights();
// Add velocity to the location.
location.add(velocity);
// Add gravity to velocity
velocity.add(gravity);
// Bounce off edges
if ((location.x > width) || (location.x < 0)) {
velocity.x = velocity.x * -1;
}
if (location.y > height) {
// We're reducing velocity ever so slightly
// when it hits the bottom of the window
velocity.y = velocity.y * -0.95;
location.y = height;
}
if (location.z < -height || location.z > 0) { //note that Zaxis goes 'into' the screen
velocity.z = velocity.z * -0.95;
//location.z = height;
}
println("location x: "+location.x);
println("location y: "+location.y);
println("location z: "+location.z);
println("velocidad x: "+velocity.x);
println("velocidad y: "+velocity.y);
println("velocidad z: "+velocity.z);
pushMatrix();
translate(width/2, height/2, 0);
modelCan.draw();
popMatrix();
}
I hope you guys can help me! Thanks!

Answer 1

The bouncing ball example is a very simple example, and I guess you can't apply it to a cylinder in an easy way.
You might want to have a look at these sites :
http://www.wildbunny.co.uk/blog/2011/04/20/collision-detection-for-dummies/
http://shiffman.net/ (his book is essential )
https://github.com/shiffman/Box2D-for-Processing (again : Daniel Shiffman)
Collision detection is made in computer time : it means that it's correlated with the frequency of your program execution. For instance, the velocity of an object can be so big that between two render cycles your first object is passing through your second object: collision detection won't happen. They didn't collide during the previous cycle, and don't collide during the current cycle.
That's why some physics "engine" like Box2D try to anticipate the collision, computing the bounding box of each object.
If you want to make accurate collision detection in 3D, you can look at the Bullet library, used in many games and movies : http://bulletphysics.org/wordpress/ but the learning curve might be large.
In your program, you can try to give a threshold to your collision detection (and add the dimensions of your object to its position, if you want the whole body to collide, not only its center !): if your object's position is between your limit and (your limit +/- a threshold) consider it's colliding, but you won't totally avoid tunnelling.