Change to return const references for TriangleMesh return values in SLAPrintObject's methods

src/libslic3r/CMakeLists.txt

@@ -156,6 +156,7 @@ add_library(libslic3r STATIC
     TriangleMesh.hpp
     utils.cpp
     Utils.hpp
+    MTUtils.hpp
     SLA/SLABoilerPlate.hpp
     SLA/SLABasePool.hpp
     SLA/SLABasePool.cpp

src/libslic3r/MTUtils.hpp

@@ -0,0 +1,63 @@
+#ifndef MTUTILS_HPP
+#define MTUTILS_HPP
+
+#include <atomic>       // for std::atomic_flag
+#include <mutex>        // for std::lock_guard
+#include <functional>   // for std::function
+#include <utility>      // for std::forward
+
+namespace Slic3r {
+
+// TODO: these classes are untested
+
+/// Handy little spin mutex for the cached meshes.
+/// Implements the "Lockable" concept
+class SpinMutex {
+    std::atomic_flag m_flg;
+    static const /*constexpr*/ auto MO_ACQ = std::memory_order_acquire;
+    static const /*constexpr*/ auto MO_REL = std::memory_order_release;
+public:
+    inline SpinMutex() { m_flg.clear(MO_REL); }
+    inline void lock() { while(m_flg.test_and_set(MO_ACQ)); }
+    inline bool try_lock() { return !m_flg.test_and_set(MO_ACQ); }
+    inline void unlock() { m_flg.clear(MO_REL); }
+};
+
+/// A wrapper class around arbitrary object that needs thread safe caching.
+template<class T> class CachedObject {
+public:
+    // Method type which refreshes the object when it has been invalidated
+    using Setter = std::function<void(T&)>;
+private:
+    T m_obj;            // the object itself
+    bool m_valid;       // invalidation flag
+    SpinMutex m_lck;    // to make the caching thread safe
+
+    // the setter will be called just before the object's const value is about
+    // to be retrieved.
+    std::function<void(T&)> m_setter;
+public:
+
+    // Forwarded constructor
+    template<class...Args> inline CachedObject(Setter fn, Args&&...args):
+        m_obj(std::forward<Args>(args)...), m_valid(false), m_setter(fn) {}
+
+    // invalidate the value of the object. The object will be refreshed at the
+    // next retrieval (Setter will be called). The data that is used in
+    // the setter function should be guarded as well if it is modified so the
+    // modification has to take place in fn.
+    inline void invalidate(std::function<void()> fn) {
+        std::lock_guard<SpinMutex> lck(m_lck); fn(); m_valid = false;
+    }
+
+    // Get the const object properly updated.
+    inline const T& get() {
+        std::lock_guard<SpinMutex> lck(m_lck);
+        if(!m_valid) { m_setter(m_obj); m_valid = true; }
+        return m_obj;
+    }
+};
+
+}
+
+#endif // MTUTILS_HPP

src/libslic3r/SLA/SLASupportTree.cpp

@@ -730,6 +730,9 @@ public:
             meshcache.merge(mesh(bs.mesh));
         }
 
+        // TODO: Is this necessary?
+        meshcache.repair();
+
         BoundingBoxf3&& bb = meshcache.bounding_box();
         model_height = bb.max(Z) - bb.min(Z);
 
@@ -1616,13 +1619,13 @@ bool SLASupportTree::generate(const PointSet &points,
     return pc == ABORT;
 }
 
-void SLASupportTree::merged_mesh(TriangleMesh &outmesh) const
+const TriangleMesh &SLASupportTree::merged_mesh() const
 {
-    outmesh.merge(get().merged_mesh());
+    return get().merged_mesh();
 }
 
 void SLASupportTree::merged_mesh_with_pad(TriangleMesh &outmesh) const {
-    merged_mesh(outmesh);
+    outmesh.merge(merged_mesh());
     outmesh.merge(get_pad());
 }
 
@@ -1658,14 +1661,12 @@ const TriangleMesh &SLASupportTree::add_pad(const SliceLayer& baseplate,
                                             double max_merge_distance_mm,
                                             double edge_radius_mm) const
 {
-    TriangleMesh mm;
-    merged_mesh(mm);
     PoolConfig pcfg;
     pcfg.min_wall_thickness_mm = min_wall_thickness_mm;
     pcfg.min_wall_height_mm    = min_wall_height_mm;
     pcfg.max_merge_distance_mm = max_merge_distance_mm;
     pcfg.edge_radius_mm        = edge_radius_mm;
-    return m_impl->create_pad(mm, baseplate, pcfg).tmesh;
+    return m_impl->create_pad(merged_mesh(), baseplate, pcfg).tmesh;
 }
 
 const TriangleMesh &SLASupportTree::get_pad() const

src/libslic3r/SLA/SLASupportTree.hpp

@@ -144,7 +144,7 @@ public:
 
     /// Get the whole mesh united into the output TriangleMesh
     /// WITHOUT THE PAD
-    void merged_mesh(TriangleMesh& outmesh) const;
+    const TriangleMesh& merged_mesh() const;
 
     void merged_mesh_with_pad(TriangleMesh&) const;
 

src/libslic3r/SLAPrint.cpp

@@ -500,7 +500,10 @@ void SLAPrint::process()
 
 SLAPrintObject::SLAPrintObject(SLAPrint *print, ModelObject *model_object):
     Inherited(print, model_object),
-    m_stepmask(slaposCount, true)
+    m_stepmask(slaposCount, true),
+    m_transformed_rmesh( [this](TriangleMesh& obj){
+            obj = m_model_object->raw_mesh(); obj.transform(m_trafo);
+        })
 {
 }
 
@@ -526,28 +529,29 @@ double SLAPrintObject::get_elevation() const {
     return ret;
 }
 
-//const std::vector<ExPolygons> &SLAPrintObject::get_support_slices() const
-//{
-//    // I don't want to return a copy but the points may not exist, so ...
-//    static const std::vector<ExPolygons> dummy_empty;
+namespace { // dummy empty static containers for return values in some methods
+const std::vector<ExPolygons> EMPTY_SLICES;
+const TriangleMesh EMPTY_MESH;
+}
 
-//    if(!m_supportdata) return dummy_empty;
-//    return m_supportdata->support_slices;
-//}
+const std::vector<ExPolygons> &SLAPrintObject::get_support_slices() const
+{
+    if(!is_step_done(slaposSliceSupports) || !m_supportdata) return EMPTY_SLICES;
+    return m_supportdata->support_slices;
+}
 
-//const std::vector<ExPolygons> &SLAPrintObject::get_model_slices() const
-//{
-//    return m_model_slices;
-//}
+const std::vector<ExPolygons> &SLAPrintObject::get_model_slices() const
+{
+    if(!is_step_done(slaposObjectSlice)) return EMPTY_SLICES;
+    return m_model_slices;
+}
 
 bool SLAPrintObject::has_mesh(SLAPrintObjectStep step) const
 {
     switch (step) {
     case slaposSupportTree:
-//        return m_supportdata && m_supportdata->support_tree_ptr && ! m_supportdata->support_tree_ptr->get().merged_mesh().empty();
 		return ! this->support_mesh().empty();
     case slaposBasePool:
-//		return m_supportdata && m_supportdata->support_tree_ptr && ! m_supportdata->support_tree_ptr->get_pad().empty();
 		return ! this->pad_mesh().empty();
 	default:
         return false;
@@ -566,22 +570,19 @@ TriangleMesh SLAPrintObject::get_mesh(SLAPrintObjectStep step) const
 	}
 }
 
-TriangleMesh SLAPrintObject::support_mesh() const
+
+
+const TriangleMesh& SLAPrintObject::support_mesh() const
 {
-    TriangleMesh trm;
-
     if(m_supportdata && m_supportdata->support_tree_ptr)
-        m_supportdata->support_tree_ptr->merged_mesh(trm);
+        return m_supportdata->support_tree_ptr->merged_mesh();
 
-    // TODO: is this necessary?
-    trm.repair();
-
-    return trm;
+    return EMPTY_MESH;
 }
 
-TriangleMesh SLAPrintObject::pad_mesh() const
+const TriangleMesh& SLAPrintObject::pad_mesh() const
 {
-    if(!m_supportdata || !m_supportdata->support_tree_ptr) return {};
+    if(!m_supportdata || !m_supportdata->support_tree_ptr) return EMPTY_MESH;
 
     return m_supportdata->support_tree_ptr->get_pad();
 }
@@ -596,11 +597,7 @@ const TriangleMesh &SLAPrintObject::transformed_mesh() const {
     // or apply an inverse transformation on the support structure after it
     // has been created.
 
-    if(m_trmesh_valid) return m_transformed_rmesh;
-    m_transformed_rmesh = m_model_object->raw_mesh();
-    m_transformed_rmesh.transform(m_trafo);
-    m_trmesh_valid = true;
-    return m_transformed_rmesh;
+    return m_transformed_rmesh.get();
 }
 
 std::vector<Vec3d> SLAPrintObject::transformed_support_points() const

src/libslic3r/SLAPrint.hpp

@@ -1,9 +1,12 @@
 #ifndef slic3r_SLAPrint_hpp_
 #define slic3r_SLAPrint_hpp_
 
+#include <mutex>
+
 #include "PrintBase.hpp"
 #include "PrintExport.hpp"
 #include "Point.hpp"
+#include "MTUtils.hpp"
 
 namespace Slic3r {
 
@@ -53,10 +56,10 @@ public:
 
     // Get a support mesh centered around origin in XY, and with zero rotation around Z applied.
     // Support mesh is only valid if this->is_step_done(slaposSupportTree) is true.
-    TriangleMesh            support_mesh() const;
+    const TriangleMesh&     support_mesh() const;
     // Get a pad mesh centered around origin in XY, and with zero rotation around Z applied.
     // Support mesh is only valid if this->is_step_done(slaposPad) is true.
-    TriangleMesh            pad_mesh() const;
+    const TriangleMesh&     pad_mesh() const;
 
     // This will return the transformed mesh which is cached
     const TriangleMesh&     transformed_mesh() const;
@@ -69,8 +72,9 @@ public:
     // as the pad height also needs to be considered.
     double get_elevation() const;
 
-//    const std::vector<ExPolygons>& get_support_slices() const;
-//    const std::vector<ExPolygons>& get_model_slices() const;
+    // Should be obvious
+    const std::vector<ExPolygons>& get_support_slices() const;
+    const std::vector<ExPolygons>& get_model_slices() const;
 
     // I refuse to grantee copying (Tamas)
     SLAPrintObject(const SLAPrintObject&) = delete;
@@ -86,7 +90,10 @@ protected:
     void                    config_apply(const ConfigBase &other, bool ignore_nonexistent = false) { this->m_config.apply(other, ignore_nonexistent); }
     void                    config_apply_only(const ConfigBase &other, const t_config_option_keys &keys, bool ignore_nonexistent = false) 
     	{ this->m_config.apply_only(other, keys, ignore_nonexistent); }
-    void                    set_trafo(const Transform3d& trafo) { m_trafo = trafo; m_trmesh_valid = false; }
+
+    void                    set_trafo(const Transform3d& trafo) {
+        m_transformed_rmesh.invalidate([this, &trafo](){ m_trafo = trafo; });
+    }
 
     bool                    set_instances(const std::vector<Instance> &instances);
     // Invalidates the step, and its depending steps in SLAPrintObject and SLAPrint.
@@ -105,8 +112,7 @@ private:
     std::vector<ExPolygons>                 m_model_slices;
 
     // Caching the transformed (m_trafo) raw mesh of the object
-    mutable TriangleMesh                    m_transformed_rmesh;
-    mutable bool                            m_trmesh_valid = false;
+    mutable CachedObject<TriangleMesh>      m_transformed_rmesh;
 
     class SupportData;
     std::unique_ptr<SupportData> m_supportdata;