initiali triangle visualization (triangles outside of the polygon are…

… rendered as well)

Arrangement_on_surface_2/demo/earth/CMakeLists.txt

@@ -76,6 +76,7 @@ source_group( "Graphics"  FILES ${source_files_graphics} )
 file(GLOB source_files_graphics_geometry
   Line_strips.h             Line_strips.cpp
   Sphere.h                  Sphere.cpp
+  Triangles.h               Triangles.cpp
   Vertices.h                Vertices.cpp
   World_coordinate_axes.h   World_coordinate_axes.cpp
  )

Arrangement_on_surface_2/demo/earth/Main_widget.cpp

@@ -159,6 +159,10 @@ void Main_widget::init_problematic_nodes()
 
 std::unique_ptr<Line_strips>   new_faces;
 
+#include "Triangles.h"
+std::unique_ptr<Triangles>  g_face_triangles;
+
+
 void Main_widget::initializeGL()
 {
   // verify that the node (180.0, -84.71338) in Antarctica is redundant
@@ -198,6 +202,7 @@ void Main_widget::initializeGL()
     auto arrh = Aos::construct(m_countries);
     auto triangle_points = Aos::get_triangles(arrh);
     qDebug() << "num triangles = " << triangle_points.size() / 3;
+    g_face_triangles = std::make_unique<Triangles>(triangle_points);
   }
 
 
@@ -474,8 +479,22 @@ void Main_widget::paintGL()
     sp.set_uniform("u_mvp", mvp);
     sp.set_uniform("u_color", m_sphere->get_color());
 
+    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
     m_sphere->draw();
 
+    // DRAW SOLID FACES
+    {
+      glDisable(GL_DEPTH_TEST);
+      QVector4D face_color(1, .5, 0, 1);
+      sp.set_uniform("u_color", face_color);
+      glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+      g_face_triangles->draw();
+
+      sp.set_uniform("u_color", QVector4D(0,0,0,1));
+      glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+      g_face_triangles->draw();
+    }
+
     sp.unuse();
   }
 

Arrangement_on_surface_2/demo/earth/Triangles.cpp

@@ -0,0 +1,79 @@
+
+#include "Triangles.h"
+
+#include <iostream>
+
+
+Triangles::Triangles(std::vector<QVector3D>& vertices) 
+{
+  initializeOpenGLFunctions();
+
+  // computer the normals of each vertex
+  std::vector<QVector3D> normals;
+  for(const auto& p : vertices)
+  {
+    auto n = p;
+    n.normalize();
+    normals.push_back(n);
+  }
+
+  int num_triangles = vertices.size() / 3;
+
+  // strided vertex-data
+  std::vector<QVector3D> vertex_data;
+  for (int i = 0; i < vertices.size(); ++i)
+  {
+    vertex_data.push_back(vertices[i]);
+    vertex_data.push_back(normals[i]);
+  }
+
+
+  // DEFINE OPENGL BUFFERS
+  glGenVertexArrays(1, &m_vao);
+  glBindVertexArray(m_vao);
+  m_num_vertices = vertices.size();
+
+  // Vertex Buffer
+  glGenBuffers(1, &m_vbo);
+  glBindBuffer(GL_ARRAY_BUFFER, m_vbo);
+  auto vertex_buffer_size = sizeof(QVector3D) * vertex_data.size();
+  auto vertex_buffer_data = reinterpret_cast<const void*>(vertex_data.data());
+  glBufferData(GL_ARRAY_BUFFER,
+              vertex_buffer_size,
+              vertex_buffer_data,
+              GL_STATIC_DRAW);
+
+  // Position Vertex-Attribute
+  GLint position_attrib_index = 0;
+  const void* position_offset = 0;
+  GLsizei stride = 6 * sizeof(float);
+  glVertexAttribPointer(position_attrib_index,
+                        3,
+                        GL_FLOAT, GL_FALSE,
+                        stride,
+                        position_offset);
+  glEnableVertexAttribArray(position_attrib_index);
+
+  // Normal Vertex-Attribute
+  GLint normal_attrib_index = 1;
+  auto* normal_offset = reinterpret_cast<const void*>(3 * sizeof(float));
+  glVertexAttribPointer(normal_attrib_index,
+                        3,
+                        GL_FLOAT,
+                        GL_FALSE,
+                        stride,
+                        normal_offset);
+  glEnableVertexAttribArray(normal_attrib_index);
+
+  glBindBuffer(GL_ARRAY_BUFFER, 0);
+  glBindVertexArray(0);
+}
+
+void Triangles::draw()
+{
+  // DRAW TRIANGLES
+  glBindVertexArray(m_vao);
+    glDrawArrays(GL_TRIANGLES, 0, m_num_vertices);
+  glBindVertexArray(0);
+}
+

Arrangement_on_surface_2/demo/earth/Triangles.h

@@ -0,0 +1,28 @@
+
+#ifndef TRIANGLES_H
+#define TRIANGLES_H
+
+#include <vector>
+#include <qvector3d.h>
+#include "Common_defs.h"
+
+
+class Triangles : protected OpenGLFunctionsBase
+{
+public:
+  // IMPORTANT: we assume that the triangles are on the sphere!
+  // this means that all vertex-normals are actually the normal vector on the
+  // sphere at the point of projection of the current vertex on the sphere.
+  Triangles(std::vector<QVector3D>& vertices);
+
+  int get_num_triangles() const;
+
+  void draw();
+
+private:
+  GLuint  m_vao, m_vbo;
+  int     m_num_vertices;
+};
+
+
+#endif