The eye transformation allows to use the coordinates relative to the viewer:
void setup() {
fullScreen(P3D);
}
void draw() {
// draw scene...
pushMatrix();
eye();
translate(0, 0, 100);
ellipse(0, 0, 50, 50);
popMatrix();
}
One can retrieve the matrix holding this transformation:
PMatrix3D eyeMat = new PMatrix3D();
void setup() {
fullScreen(P3D);
}
void draw() {
// ...
getEyeMatrix(eyeMat);
// ...
}