Hi,
it may seem strange, that a function as simple as get() causes discordance in my mind, but I think that maybe the problem lies somewhere else.
I'm using processing for two or three days now and in my little first draft of a first program, which I've uploaded here http://fnork.ath.cx/boincview.tar.gz I want the Donuts to know if the cursor is over them. The only idea I have had so far was to check whether the color under the cursor contains any red and if so to calculate which donut is the nearest. From this problem two alternating questions derive:
1. Why does red(get(mouseX,mouseY)) return these (for me) unexpected results (red on black areas, black on red areas or vice versa), or
2. How to solve this problem more elegantly?

Thanks a lot in advance!

boincview.pde:
Code:

import damkjer.ocd.*;
import processing.opengl.*;

Camera cam;
MouseWheelEventDemo wheel;
ArrayList donuts = new ArrayList();

public static void main( String args[] ) {
  PApplet.main( new String[] { "--present", "boincview" } );
} 

void setup()
{
  size(600,600,OPENGL);
  colorMode(RGB,255,255,255,255);
  frameRate(24);
  wheel = new MouseWheelEventDemo();
  cam = new Camera(this);
  this.donuts.add(new Donut(0.95,10000.0));
  this.donuts.add(new Donut(0.75,10000.0));
  noStroke();
  noSmooth();
}

void draw() { 
  background(0);
  cam.feed();
  lights();
  for(int i=0; i<this.donuts.size(); i++){
    Donut d = (Donut) this.donuts.get(i);
    d.draw();
  }
  println(red(get(mouseX,mouseY)));  // Testing
  if(mouseX < 32) cam.pan(-(32-mouseX)/1000.0);
  if(mouseX > width-32) cam.pan((32-(width-mouseX))/1000.0);
  if(mouseY < 32) cam.tilt(-(32-mouseY)/1000.0);
  if(mouseY > height-32) cam.tilt((32-(height-mouseY))/1000.0);
}

public class MouseWheelEventDemo implements MouseWheelListener {
  int notches = 0;
  public MouseWheelEventDemo() {
    addMouseWheelListener(this);
  }
  public void mouseWheelMoved(MouseWheelEvent e) {
    cam.zoom(-e.getWheelRotation()/20.0);
  }
} 
 

Donut.pde:
Code:

public class Donut {
  String computer = "";
  float fraction = 0.0;
  float remaining = 0.0;
  float radius = 0.0;
  float posX = 0;
  float posY = 0;
  float posZ = 0;
  boolean isHovering = false;

  public Donut(float frac, float remain){
    this.fraction = frac;
    this.remaining = remain;
    this.radius = remaining/(1-fraction)/3600;
    this.posX = random(-600,600);
    this.posY = random(-600,600);
    this.posZ = random(-100,100);
    //println(screenX(this.posX,this.posY,this.posZ) + " " + screenY(this.posX,this.posY,this.posZ));  // Testing
  }
  
  void draw(){
    pushMatrix();
    translate(this.posX,this.posY,this.posZ);
    float theta;
    int full = floor(this.fraction*16);
    int transp = 255;
    pushMatrix();
    for(int i=0;i<16;i++){
	if(i==full) transp = 64;
	theta = TWO_PI/16*i;
	translate(cos(theta)*this.radius,sin(theta)*this.radius,0);
	fill(200+round(sin(2*theta)*40),0,0,transp);
	sphere(TWO_PI*this.radius/8);
    }
    popMatrix();
    popMatrix();
  }
  
  public float getX(){
    return posX;
  }

  public float getY(){
    return posY;
  }

  public float getZ(){
    return posZ;
  }
  
  public float getRadius(){
    return radius;
  }

}
 

Done.
Thanks for your interest.

To speed up the color grabbing use pixels[] with bit shifting instead.

http://processing.org/reference/leftshift.html