Fixed|BSP Builder|ConvexSubspace: Failed to partition a map with over…

…lapped single sided lines

When two or more single sided lines are overlapping and reference the
same sector, depending on how the map is partitioned it may result in
a degenerate set of line segments. In this situation, separating the
discordant segs into an "extra" mesh geometry may mean we are left
with fewer than three to produce the primary convex polygon geometry
for a BSP leaf. In which case, we shouldn't attempt to assign a non-
convex polygon.

BLUDWRKS.wad once again loads (and very nearly rendered correctly).

doomsday/client/include/world/sector.h

@@ -369,12 +369,6 @@ class Sector : public de::MapElement
      */
     inline int clusterCount() const { return clusters().count(); }
 
-    /**
-     * Convenient method of determning whether the sector is a parent of one or
-     * BSP leaf (i.e., at least one cluster is defined).
-     */
-    inline bool hasBspLeafs() const { return clusterCount() != 0; }
-
     /**
      * (Re)Build BSP leaf clusters for the sector.
      */

doomsday/client/src/render/walledge.cpp

@@ -142,7 +142,9 @@ DENG2_PIMPL(WallEdge), public IHPlane
             (line.definesPolyobj()? &line.polyobj().bspLeaf()
                                   : &hedge->face().mapElement()->as<BspLeaf>())->clusterPtr();
 
-        if(seg.lineSide().considerOneSided())
+        if(seg.lineSide().considerOneSided() ||
+           // Mapping errors may result in a line segment missing a back face.
+           (!line.definesPolyobj() && !hedge->twin().hasFace()))
         {
             if(spec.section == LineSide::Middle)
             {

doomsday/client/src/world/bsp/convexsubspace.cpp

@@ -380,10 +380,9 @@ void ConvexSubspace::addOneSegment(LineSegment::Side const &newSegment)
 void ConvexSubspace::buildGeometry(BspLeaf &leaf, Mesh &mesh) const
 {
     LOG_AS("ConvexSubspace::buildGeometry");
-    bool const isDegenerate = segmentCount() < 3;
 
     // Sanity check.
-    if(!isDegenerate && !d->haveMapLineSegment())
+    if(segmentCount() >= 3 && !d->haveMapLineSegment())
         throw Error("ConvexSubspace::buildGeometry", "No map line segment");
 
     if(d->needRebuildOrderedSegments)
@@ -415,6 +414,7 @@ void ConvexSubspace::buildGeometry(BspLeaf &leaf, Mesh &mesh) const
         conty->addOneSegment(oseg);
     }
 
+    int extraMeshSegments = 0;
     for(int i = 0; i < continuities.count(); ++i)
     {
         Continuity &conty = continuities[i];
@@ -441,6 +441,9 @@ void ConvexSubspace::buildGeometry(BspLeaf &leaf, Mesh &mesh) const
 
                 HEdge *hedge = extraMesh->newHEdge(lineSeg->from());
                 LineSideSegment *seg = mapSide->addSegment(*hedge);
+
+                extraMeshSegments += 1;
+
 #ifdef __CLIENT__
                 /// @todo LineSide::newSegment() should encapsulate:
                 seg->setLineSideOffset(Vector2d(mapSide->from().origin() - lineSeg->from().origin()).length());
@@ -519,7 +522,7 @@ void ConvexSubspace::buildGeometry(BspLeaf &leaf, Mesh &mesh) const
     }
 #endif*/
 
-    if(!isDegenerate)
+    if(segmentCount() - extraMeshSegments >= 3)
     {
         // Construct a new face and a ring of half-edges.
         Face *face = mesh.newFace();
@@ -529,6 +532,7 @@ void ConvexSubspace::buildGeometry(BspLeaf &leaf, Mesh &mesh) const
         {
             LineSegment::Side *lineSeg = d->orderedSegments[i].segment;
 
+            // Already added this to an extra mesh?
             if(lineSeg->hasHEdge())
                 continue;