The active section box of SectionPlanes.startSectionBox, null without one; hidden lists the faces that
are not drawn (SectionPlane.setVisible), none when left out
The enabled planes, oldest first, each in its slot (0..5): a point on the plane and its normal, which points to the side that is cut away, the name it is listed by (SectionPlane.getName), the standard plane it is (SectionPlane.getStandard) and whether it is drawn (SectionPlane.isVisible). getState gives every field; setState takes a plane without name, standard or visible (drawn)
How section planes cut the model, SectionPlanes.getState and SectionPlanes.setState. Render frame, mm