Fix tree support related crash that occurs if there are no overhangs (U…

…ltimaker#2028)

include/TreeSupport.h

@@ -74,8 +74,9 @@ class TreeSupport
      *
      * \param storage[in] Background storage to access meshes.
      * \param currently_processing_meshes[in] Indexes of all meshes that are processed in this iteration
+     * \return Uppermost layer precalculated. -1 if no layer were precalculated as no overhang is present.
      */
-    void precalculate(const SliceDataStorage& storage, std::vector<size_t> currently_processing_meshes);
+    LayerIndex precalculate(const SliceDataStorage& storage, std::vector<size_t> currently_processing_meshes);
 
 
     /*!

src/TreeModelVolumes.cpp

@@ -1084,7 +1084,6 @@ void TreeModelVolumes::calculateAvoidanceToModel(const std::deque<RadiusLayerPai
             {
                 return;
             }
-            getPlaceableAreas(radius, max_required_layer); // ensuring Placeableareas are calculated
             const coord_t offset_speed = slow ? max_move_slow_ : max_move_;
             const coord_t max_step_move = std::max(1.9 * radius, current_min_xy_dist_ * 1.9);
             Polygons latest_avoidance;
@@ -1100,12 +1099,13 @@ void TreeModelVolumes::calculateAvoidanceToModel(const std::deque<RadiusLayerPai
                                  : critical_avoidance_cache_to_model_));
                 start_layer = 1 + getMaxCalculatedLayer(radius, slow ? avoidance_cache_to_model_slow_ : holefree ? avoidance_cache_hole_to_model_ : avoidance_cache_to_model_);
             }
+            start_layer = std::max(start_layer, LayerIndex(1));
             if (start_layer > max_required_layer)
             {
-                spdlog::debug("Requested calculation for value already calculated ?");
+                spdlog::debug("Requested calculation for value already calculated or max_required_layer is 0?");
                 return;
             }
-            start_layer = std::max(start_layer, LayerIndex(1));
+            getPlaceableAreas(radius, max_required_layer); // ensuring Placeable Areas are calculated
             latest_avoidance
                 = getAvoidance(radius, start_layer - 1, type, true, true); // minDist as the delta was already added, also avoidance for layer 0 will return the collision.
 

src/TreeSupport.cpp

@@ -155,7 +155,12 @@ void TreeSupport::generateSupportAreas(SliceDataStorage& storage)
             exclude);
 
         // ### Precalculate avoidances, collision etc.
-        precalculate(storage, processing.second);
+        const LayerIndex max_required_layer = precalculate(storage, processing.second);
+        if(max_required_layer < 0)
+        {
+            spdlog::info("Support tree mesh group {} does not have any overhang. Skipping tree support generation for this support tree mesh group.",counter + 1);
+            continue; //If there is no overhang to support, skip these meshes
+        }
         const auto t_precalc = std::chrono::high_resolution_clock::now();
 
         // ### Place tips of the support tree
@@ -208,10 +213,10 @@ void TreeSupport::generateSupportAreas(SliceDataStorage& storage)
     storage.support.generated = true;
 }
 
-void TreeSupport::precalculate(const SliceDataStorage& storage, std::vector<size_t> currently_processing_meshes)
+LayerIndex TreeSupport::precalculate(const SliceDataStorage& storage, std::vector<size_t> currently_processing_meshes)
 {
     // Calculate top most layer that is relevant for support.
-    LayerIndex max_layer = 0;
+    LayerIndex max_layer = -1;
     for (size_t mesh_idx : currently_processing_meshes)
     {
         const SliceMeshStorage& mesh = *storage.meshes[mesh_idx];
@@ -240,7 +245,11 @@ void TreeSupport::precalculate(const SliceDataStorage& storage, std::vector<size
     }
 
     // ### The actual precalculation happens in TreeModelVolumes.
-    volumes_.precalculate(max_layer);
+    if(max_layer >= 0)
+    {
+        volumes_.precalculate(max_layer);
+    }
+    return max_layer;
 }