There are 4 render modes in Processing 2.0:
default ("slow" but very accurate 2D render mode)
P2D (OPENGL, faster but less accurate 2D render mode)
P3D (OPENGL and well, 3D)
PDF (for PDF output)
default | P2D | P3D
Code I used to create these images:
void setup() {
//size(200, 200);
//size(200, 200, P2D);
size(200, 200, P3D);
}
void draw() {
background(153);
strokeWeight(10);
ellipse(100, 100, 100, 100);
}
You can find a more detailed explanation including a guide on choosing the right mode at What is P3D?