Fills the flat cross-section where the clipping plane cuts a solid, so a
clipped closed solid reads as a slice instead of a hollow shell. For a
volumetric input (a Linear_cell_complex) each volume's cross-section is
filled in that volume's color.
The clipped solid is drawn into the stencil with an even-odd rule and a
quad on the plane is filled where the stencil is odd. Per-volume color
uses a dedicated cap buffer (POS_CAP_FACES) holding each volume's full
closed boundary (shared walls kept, unlike the de-duplicated display
buffer), so each volume is closed on its own; a surface mesh has no
groups and caps grey from the display buffer. The stencil buffer is
requested in init_ogl_context.
Draft: a K key toggles the cap, the cap buffer is built eagerly, and
only the two solid clip modes are capped.
Rajdeep Singh
e48c71296d