Processing is double-buffered by default. If you're seeing tearing, then something weird is going on.

Thanks for the responses.

@JohnG: I looked at the code for PApplet, and it is indeed double-buffered. That answers a lot of my questions.

@fjen: Unfortunately, this didn't work. The animation can run at 60fps, but even at 1fps I get tearing.

I should clarify and say that on most of the frames I do not get tearing (but I get it on some).
I think my problem is that the canvas is so large, at 1280 x 720 (the resolution of the projector I will be using). I would think that the problem is that blitting the image takes too long, and occasionally gets interrupted to read the image. Except that paint() is synchronized. I did try making my draw routine synchronized, no help.

I am going to do some additional research, and since the code is so simple, I will probably implement in Java without Processing. I think that I want to try using BufferStrategy, which apparently blits or flips the buffer right after vsync. There are some articles out there on the web. When I get something that solves my issue I will post in this thread.

Also, I should say that I have very sudden color transitions (from bright red to white, say) and I get choppiness. I am going to try motion blur.

I got it working. Right now it is a class that extends PApplet. I'd like to package it as another renderer, which should be possible. If I do that I'll post it to the libraries category. Here's a description

Q: What does it do?
A: Solves issue of tearing in certain animations.

Q: How does it do it?
A: Uses BufferStrategy, which aligns buffer flips to vsync. This is an active rendering strategy (where the program pushes data to the graphics system) rather than a passive rendering system (where the graphics system issues requests and pulls data from the program -- done in java with paint()/update()).

For more info on active and passive rendering and the "fullscreen exclusive mode API": http://java.sun.com/docs/books/tutorial/extra/fullscreen/index.html

I had a problem with this too... here's a sound-reactive program I wrote... it was having problems with tearing. I found something in a forum thread, somewhere.... that allowed me to turn on vsync which fixed the problem. I've posted the whole program but you can see the vsync bit at the start and in setup. I hope this helps.

[EDIT-If you want to see this program working you need a working microphone which is successfully detected by Minim. Try turning off the openGL stuff to see the horrible tearing]

Code:

import ddf.minim.analysis.*;
import ddf.minim.*;
import processing.opengl.*;
import javax.media.opengl.GL;
Minim minim;
AudioInput in;
FFT fft;
//PrintWriter output;
float[] bands;
float amplitude=0;
float h, s, b; //hue saturation, brightness
PGraphicsOpenGL pgl; //need to use this to stop screen tearing
GL gl;


void setup()
{
  size(640, 480, OPENGL);
  pgl = (PGraphicsOpenGL) g; //processing graphics object
  gl = pgl.beginGL(); //begin opengl
  gl.setSwapInterval(1); //set vertical sync on
  pgl.endGL(); //end opengl
  background(0);
  frameRate(30);
  //output= createWriter("sounddata.txt");
  bands = new float[10];
  minim = new Minim(this); 
  in = minim.getLineIn(Minim.STEREO, 512);
  fft= new FFT(in.bufferSize(), in.sampleRate());
  fft.logAverages(22, 1);
  colorMode(HSB, 255, 255, 255);
}


void draw()
{
  amplitude=0; 
  fft.forward(in.mix); 
   for(int i=0; i<fft.avgSize(); i++)
   {
	bands[i]=fft.getAvg(i);
   }
   
   s = (bands[0] + bands[1] + bands[2] + bands[3])/4;
   b =  (bands[4] + bands[5] + bands[6])/3;
   h=  (bands[7] + bands[8] + bands[9])/3;
   
   for(int i=0; i<10; i++)
   {
     amplitude+= bands[i];
   }
   
   s= map(s, 0.88, 1, 0, 255);
   b = map(b, 0.026, 1, 0, 255);
   h= map(h, 0.011, 0.5, 0, 255);
   
   color c = color(h, s, b);
   loadPixels();
   for (int i=0; i< pixels.length; i++)
   {
     pixels[i]=c;
   }
   updatePixels();
}