Example of structuring your Processing sketch to avoid having to restart everything.

gistfile1.java

void setup ()
{
	size(width, height, P3D);
	thread("update");
}

void update ()
{
	while (true) {
		try {
			// do my sketching into a separate context, like an int[]
			Thread.sleep(30);
		} catch (Exception e) {
		}
	}
}

void draw ()
{
  // do my drawing
}