I'm trying to change the contents of an image in the draw loop, but I guess my understanding of the PImage format is lacking.

For example, I want to do a variation of the noise3D example. Rather than alter the display pixels directly as in the example, I want to store the noise values in an image var and then display that image. Here's my version of that example:

-------------

PImage img;

float increment = 0.01;
float zoff = 0;
float zinc = 0.2;
   
void setup()
{
 img = loadImage("blah.jpg");
 int xsize = img.width;
 int ysize = img.height;
 size(xsize, ysize);
 background(0);

 // black out img
 loadPixels();
 for (int i=0; i<(width*height); i++) {
   img.pixels[i] = color(0,0,0);
 }
 updatePixels();
}

void draw()
{
 // load up img with new values
 loadPixels();
 float xoff = 0.0f;
 for (int x = 0; x < width; x++) {
   xoff += increment;
   float yoff = 0.0f;
   for (int y = 0; y < height; y++) {
     yoff += increment;
     float bright = noise(xoff,yoff,zoff)*255;
     img.pixels[x+y*width] = color(bright,bright,bright);
   }
 }
 updatePixels();
 // display img
 image(img,0,0);
 
 zoff += zinc;
}


--------------

My question is, why doesn't this update? I'm under the impression that I should be able to use the "img.pixels[index] = whatever" command to change the contents of img in the draw loop.

Just to clarify, what I'd like to do is:

a) initialize an image variable
b) change the contents of that image (such as with noise)
c) display that image
d) loop back to b.

Any help is appreciated!
Mark

Bingo!

I didn't understand that loadPixels() and updatePixels() could be used that way.

thanks,
Mark