I'm using the nyARToolkit's nyARBoard. When calling the beginTransform to set the correct transformation matrix to transform the overlayed graphics, all objects being rendered after a call to the endTransform() method are also transformed.
PGraphicsOpenGL pgl = (PGraphicsOpenGL) g;
nya.beginTransform(pgl);
.... stuff to transform
nya.endTransform();
..objects here are still being transformed until draw() is finished with it's cycle.