From 4f423bf555d6fb2327ef12f0cb804e3944fcb000 Mon Sep 17 00:00:00 2001
From: wmayer <wmayer@users.sourceforge.net>
Date: Mon, 9 Dec 2019 20:06:48 +0100
Subject: [PATCH] implement algorithmic solution to determine whether triangle
 is visible

---
 src/Mod/Mesh/Gui/ViewProvider.cpp | 68 +++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/src/Mod/Mesh/Gui/ViewProvider.cpp b/src/Mod/Mesh/Gui/ViewProvider.cpp
index 333672060f..935e815039 100644
--- a/src/Mod/Mesh/Gui/ViewProvider.cpp
+++ b/src/Mod/Mesh/Gui/ViewProvider.cpp
@@ -54,6 +54,11 @@
 # include <Inventor/nodes/SoTransform.h>
 #endif
 
+#include <QFuture>
+#include <QFutureWatcher>
+#include <QtConcurrentMap>
+#include <boost/bind.hpp>
+
 /// Here the FreeCAD includes sorted by Base,App,Gui......
 #include <Base/Console.h>
 #include <Base/Exception.h>
@@ -1328,9 +1333,71 @@ void ViewProviderMesh::renderGLCallback(void * ud, SoAction * action)
     }
 }
 
+namespace MeshGui {
+
+class Vertex
+{
+public:
+    Vertex(const MeshCore::MeshKernel& kernel,
+           const MeshCore::MeshFacetGrid& grid,
+           const Base::Vector3f& pos)
+    : kernel(kernel)
+    , grid(grid)
+    , pos(pos)
+    {
+    }
+    bool visible(const Base::Vector3f& base) const
+    {
+        MeshCore::MeshAlgorithm meshAlg(kernel);
+        bool ok = meshAlg.IsVertexVisible(base, pos, grid);
+        return ok;
+    }
+
+private:
+    const MeshCore::MeshKernel& kernel;
+    const MeshCore::MeshFacetGrid& grid;
+    Base::Vector3f pos;
+};
+
+}
+
 std::vector<unsigned long> ViewProviderMesh::getVisibleFacets(const SbViewportRegion& vp,
                                                               SoCamera* camera) const
 {
+#if 1
+    Q_UNUSED(vp)
+
+    SbVec3f pos = camera->position.getValue();
+
+    const Mesh::PropertyMeshKernel& meshProp = static_cast<Mesh::Feature*>(pcObject)->Mesh;
+    const Mesh::MeshObject& mesh = meshProp.getValue();
+
+    const MeshCore::MeshKernel& kernel = mesh.getKernel();
+    MeshCore::MeshFacetGrid grid(kernel);
+
+    std::vector<Base::Vector3f> points;
+    points.reserve(kernel.CountFacets());
+    for (unsigned long i = 0; i < kernel.CountFacets(); i++) {
+        points.push_back(kernel.GetFacet(i).GetGravityPoint());
+    }
+
+    Vertex v(kernel, grid, Base::convertTo<Base::Vector3f>(pos));
+    QFuture<bool> future = QtConcurrent::mapped
+        (points, boost::bind(&Vertex::visible, &v, _1));
+    QFutureWatcher<bool> watcher;
+    watcher.setFuture(future);
+    watcher.waitForFinished();
+
+    unsigned long index = 0;
+    std::vector<unsigned long> faces;
+    for (QFuture<bool>::const_iterator i = future.begin(); i != future.end(); ++i, index++) {
+        if ((*i)) {
+            faces.push_back(index);
+        }
+    }
+
+    return faces;
+#else
     const Mesh::PropertyMeshKernel& meshProp = static_cast<Mesh::Feature*>(pcObject)->Mesh;
     const Mesh::MeshObject& mesh = meshProp.getValue();
     uint32_t count = (uint32_t)mesh.countFacets();
@@ -1398,6 +1465,7 @@ std::vector<unsigned long> ViewProviderMesh::getVisibleFacets(const SbViewportRe
     faces.erase(std::unique(faces.begin(), faces.end()), faces.end());
 
     return faces;
+#endif
 }
 
 void ViewProviderMesh::cutMesh(const std::vector<SbVec2f>& picked,