There are a number of overloaded ofNoise() functions that depend on two, three, or four parameters: ofNoise( x, y ), ofNoise( x, y, z ), and ofNoise( x, y, z, t ). They have behavior like ofNoise( t ) but use several input parameters. Their coordinates may be scaled as 2D or 3D space coordinates of some point and may even include time. So such functions give a way for generating 2D, 3D, and 4D fields with coherently changing values that are static or evolving with time. For example, the ofNoise( x, y ) function can be used for drawing a smooth random texture in the following way:

float scaleX = 0.007;    //1.0 / scaleX is coherence in x
float scaleY = 0.008;    //1.0 / scaleY is coherence in y
float posX0 = 593.2;
float posY0 = 43.7;
for (int y=0; y<500; y++) {
  for (int x=0; x<500; x++) {
    float value = ofNoise( x*scaleX+posX0, y*scaleY+posY0 );
    ofSetColor( value*255, value*255, value*255 );
    ofRect( x, y, 1, 1 );
  }
}

On running the code, you will see the following texture:

Now add the third parameter in the calling function ofNoise(), which increases with time, and you will obtain a texture that slowly evolves with time.

float value = ofNoise( x*scaleX+posX0, y*scaleY+posY0,
                      time*0.1 + 445.6 );

This code is simple and great for demonstrating the idea. But it works extremely slowly because we render each texture's pixel as a separate rectangle with size 1 × 1. To obtain real-time performance, prepare the texture colors in the ofImage image object and draw it in one step using image.draw() (see the Creating images section in Chapter 4, Images and Textures).

A similar technique can be used for generating values for evolving height maps of 3D surfaces (see The oscillating plane example section in Chapter 7, Drawing in 3D).