fix(track): 3D sleepers let go of the beams of the tracks far away

world/SleeperWorker.cpp

@@ -227,4 +227,10 @@ void settle_background() {
     worker().settle();
 }
 
+void forget_layout( TTrack const &Track ) {
+
+    std::lock_guard<std::mutex> lock { clusters_mutex() };
+    known_clusters().erase( &Track );
+}
+
 } // namespace track_sleepers

world/SleeperWorker.h

@@ -27,5 +27,8 @@ bool in_background();
 void ask_layout( TTrack &Track );
 // nothing left to work out in the background nor being worked out, the waiting ones dropped
 void settle_background();
+// the layout of the cluster kept for the track let go, once the track laid its beams or went far; the cluster stays while
+// another track of it keeps it
+void forget_layout( TTrack const &Track );
 
 } // namespace track_sleepers

world/Track.cpp

@@ -1542,7 +1542,8 @@ void TTrack::create_geometry( gfx::geometrybank_handle const &Bank ) {
     m_sleepers3d.active = track_sleepers::lays( *this );
     // bake per-instance sleeper transforms now that the owning cell has assigned m_origin.
     // safe to call here even if the track has no sleepermodel (early-outs internally).
-    if( m_sleeper_enabled && m_sleeper_local_transforms.empty() ) {
+    // a track laying the 3D sleepers draws its sleeper model with them, the transforms of the model alone wouldn't be drawn
+    if( m_sleeper_enabled && false == m_sleepers3d.active && m_sleeper_local_transforms.empty() ) {
         build_sleeper_transforms();
     }
     switch (iCategoryFlag & 15)

world/TrackSleepers.cpp

@@ -22,6 +22,7 @@ http://mozilla.org/MPL/2.0/.
 
 #include <glm/gtc/matrix_transform.hpp>
 
+#include <algorithm>
 #include <map>
 #include <set>
 
@@ -111,7 +112,6 @@ void lay( TTrack &Track ) {
     }
     laid.whole.clear();
     laid.plain.clear();
-    laid.beams.clear();
     laid.chunks.clear();
     laid.timbers = timber_model( Track );
     laid.plains = plain_model( Track );
@@ -125,9 +125,10 @@ void lay( TTrack &Track ) {
             + to_string( panel.second, 2 ) + " m along, where they share the timbers of its panel" );
     }
     laid.laying = true;
-    laid.beams = ( in_background() ? std::move( placed ) : place( Track ) );
+    auto const beams { in_background() ? std::move( placed ) : place( Track ) };
     laid.laying = false;
-    auto const &beams { laid.beams };
+    // the layout of the cluster isn't needed by this track any more, the instances below are what's drawn
+    forget_layout( Track );
 
     auto const partlength = [&]( int const Part ) {
         return static_cast<double>( parts.spans[ Part ].y - parts.spans[ Part ].x ); };
@@ -233,6 +234,47 @@ void lay( TTrack &Track ) {
         }
     }
     close_run();
+    // kept for as long as the track is near, without the room the vectors grew into
+    for( auto &instances : laid.instances ) {
+        instances.shrink_to_fit();
+    }
+    laid.whole.shrink_to_fit();
+    laid.plain.shrink_to_fit();
+    laid.chunks.shrink_to_fit();
+}
+
+void release_far( glm::dvec3 const &Camera, double const Range ) {
+
+    // the tracks swept in slices, so a big scenery costs little in a frame
+    static std::size_t next { 0 };
+    auto const &tracks { simulation::Paths.sequence() };
+    auto const slice { std::min<std::size_t>( tracks.size(), 256 ) };
+    for( std::size_t count = 0; count < slice; ++count ) {
+        if( next >= tracks.size() ) {
+            next = 0;
+        }
+        auto *track { tracks[ next++ ] };
+        if( track == nullptr || false == track->m_sleepers3d.active || track->m_sleepers3d.laying ) {
+            continue;
+        }
+        if( glm::length( track->location() - Camera ) - track->radius() <= Range ) {
+            continue;
+        }
+        auto &laid { track->m_sleepers3d };
+        forget_layout( *track );
+        auto const holds { laid.chunks.capacity() > 0 || laid.whole.capacity() > 0 || laid.plain.capacity() > 0
+            || std::any_of( laid.instances.begin(), laid.instances.end(), []( std::vector<glm::mat4> const &Instances ) { return Instances.capacity() > 0; } ) };
+        if( false == holds ) {
+            continue;
+        }
+        for( auto &instances : laid.instances ) {
+            std::vector<glm::mat4> {}.swap( instances );
+        }
+        std::vector<glm::mat4> {}.swap( laid.whole );
+        std::vector<glm::mat4> {}.swap( laid.plain );
+        std::vector<chunk> {}.swap( laid.chunks );
+        laid.dirty = true;
+    }
 }
 
 layout_check check() {

world/TrackSleepers.h

@@ -86,7 +86,6 @@ struct laid {
     std::vector<glm::mat4> whole; // transforms of the timbers of a model without parts, drawn whole
     std::vector<glm::mat4> plain; // transforms of the plain sleepers, whole models, relative to the origin of the track
     std::vector<chunk> chunks;
-    std::vector<beam> beams; // as they're laid
 };
 
 // how far the ballast of a track with beams is lowered, so they stick out of it
@@ -130,6 +129,9 @@ void unsettle_around( TTrack &Track );
 void lay_in_background( bool const Background );
 // the beams of the track worked out ahead, before it comes in range
 void prefetch( TTrack &Track );
+// the beams of the tracks far from the camera let go, a slice of the tracks each call, to be laid again as they come near;
+// otherwise each track keeps the beams laid since it was first seen
+void release_far( glm::dvec3 const &Camera, double const Range );
 
 // what's wrong with the layout of the beams of all the tracks: beams over each other, rails with too few beams under them,
 // timbers shared by rails out of one plane