qbsp: add sphere bounds for bspbrush_t

include/qbsp/brush.hh

@@ -68,6 +68,9 @@ struct bspbrush_t {
     std::optional<uint32_t> outputnumber; /* only set for original brushes */
     mapentity_t *func_areaportal;
 
+    qvec3d sphere_origin;
+    double sphere_radius;
+
     void update_bounds();
 
     std::unique_ptr<bspbrush_t> copy_unique() const;

qbsp/brush.cc

@@ -1096,4 +1096,7 @@ void bspbrush_t::update_bounds()
     for (const auto &face : sides) {
         this->bounds = this->bounds.unionWith(face.w.bounds());
     }
+
+    this->sphere_origin = (bounds.mins() + bounds.maxs()) / 2.0;
+    this->sphere_radius = qv::length((bounds.maxs() - bounds.mins()) / 2.0);
 }