I took out the clamping code for the portal, and instead test the portal's points vs the near plane of the frustum, and if it's fully outside ( possible if the camera is one on side of the portal and the player on the other ) or partially clipped, then I just use the existing viewport and don't try to clip or clamp it. This fixed the issue of dropouts.
I further simplified the portal / cell layout this weekend. Instead of the cells looking for neighbor cells via overlap, and portals in the cell/cell intersection area, I switched to a much more forgiving and simpler portal-based approach.
Fow now I removed the detection of cell neighbors, but will add it in later as a rarely-used method where the designer can flag certain cells as neighbors via facets.
I ran into issues with the portals when a cell partly overlapped many portals. The new scheme takes each portal, grows it by 2 meters in each dimension, and queries for intersecting cells. It then walks through these cells and takes the 2 with the largest volume intersection with the expanded portal as the two cells conntected by the portal. This way if a cell overlaps a corner of a portal, it doesn't matter, and the cells don't even have to exactly touch the portal to be hooked up.
Right now I'm debugging a fog culling issue, and drinking Diet Dr. Skipper. This is sooo glamorous. ;)
