Added: world coordinate axes

Arrangement_on_surface_2/demo/earth/CMakeLists.txt

@@ -22,6 +22,7 @@ qt_add_executable(earth
     Shader_program.h  Shader_program.cpp
     Sphere.h          Sphere.cpp
     Tools.h
+    World_coordinate_axes.h   World_coordinate_axes.cpp
 )
 
 

Arrangement_on_surface_2/demo/earth/World_coordinate_axes.cpp

@@ -0,0 +1,76 @@
+
+#include "World_coordinate_axes.h"
+
+#include <qvector3d.h>
+
+#include <vector>
+
+
+World_coord_axes::World_coord_axes(float length)
+{
+  initializeOpenGLFunctions();
+
+  const auto a = length;
+  const float c = 0.0;
+  std::vector<QVector3D> vertex_data {
+    QVector3D(0,0,0), QVector3D(1,0,0),
+    QVector3D(a,0,0), QVector3D(1,0,0),
+
+    QVector3D(0,0,0), QVector3D(0,1,0),
+    QVector3D(0,a,0), QVector3D(0,1,0),
+
+    QVector3D(0,0,0), QVector3D(c,c,1),
+    QVector3D(0,0,a), QVector3D(c,c,1)
+  };
+
+
+  // DEFINE OPENGL BUFFERS
+  glGenVertexArrays(1, &m_vao);
+  glBindVertexArray(m_vao);
+
+
+  // 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);
+
+  // Color Vertex-Attribute
+  GLint color_attrib_index = 1;
+  auto* color_offset = reinterpret_cast<const void*>(3 * sizeof(float));
+  glVertexAttribPointer(color_attrib_index,
+                        3,
+                        GL_FLOAT,
+                        GL_FALSE,
+                        stride,
+                        color_offset);
+  glEnableVertexAttribArray(color_attrib_index);
+
+  glBindBuffer(GL_ARRAY_BUFFER, 0);
+  glBindVertexArray(0);
+}
+
+void World_coord_axes::draw()
+{
+  glBindVertexArray(m_vao);
+  {
+    const int count = 2 * 3; // = 2 * number of lines
+    glDrawArrays(GL_LINES, 0, count);
+  }
+  glBindVertexArray(0);
+}

Arrangement_on_surface_2/demo/earth/World_coordinate_axes.h

@@ -0,0 +1,21 @@
+
+#ifndef WORLD_COORD_AXES_H
+#define WORLD_COORD_AXES_H
+
+#include "Common_defs.h"
+#include <qvector4d.h>
+
+
+class World_coord_axes : protected OpenGLFunctionsBase
+{
+public:
+  World_coord_axes(float length);
+
+  void draw();
+
+private:
+  GLuint    m_vao, m_vbo;
+};
+
+
+#endif

Arrangement_on_surface_2/demo/earth/mainwidget.cpp

@@ -82,6 +82,13 @@ void MainWidget::initializeGL()
   m_timer.start(12, this);
 }
 
+
+
+
+#include "World_coordinate_axes.h"
+std::unique_ptr<World_coord_axes> m_world_coord_axes;
+
+
 void MainWidget::init_camera()
 {
   m_camera.set_pos(0, 0, 10);
@@ -94,6 +101,9 @@ void MainWidget::init_geometry()
   m_sphere = std::make_unique<Sphere>(num_slices, num_stacks, r);
   const float c = 0.8;
   m_sphere->set_color(c, c, c, 1);
+
+
+  m_world_coord_axes = std::make_unique<World_coord_axes>(5);
 }
 void MainWidget::init_shader_programs()
 {
@@ -147,10 +157,10 @@ void MainWidget::paintGL()
   const auto mvp = projection * view * model;
 
   // Clear color and depth buffer
-  //auto& sp = m_sp_smooth;
-  auto& sp = m_sp_color_only;
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+  // SPHERE
   {
+    auto& sp = m_sp_smooth;
     sp.use();
     sp.set_uniform("u_mvp", mvp);
     sp.set_uniform("u_color", m_sphere->get_color());
@@ -159,4 +169,15 @@ void MainWidget::paintGL()
 
     sp.unuse();
   }
+
+  // WORLD COORDINATE AXES
+  {
+    auto& sp = m_sp_color_only;
+    sp.use();
+    sp.set_uniform("u_mvp", mvp);
+
+    m_world_coord_axes->draw();
+
+    sp.unuse();
+  }
 }

Arrangement_on_surface_2/demo/earth/shaders/color_only_fs.glsl

@@ -1,13 +1,11 @@
 
 #version 330
 
-uniform vec4 u_color;
-
-
+in vec3 v_color;
 out vec4 out_color;
 
 
 void main()
 {
-	out_color = u_color;
+	out_color = vec4(v_color, 1);
 }

Arrangement_on_surface_2/demo/earth/shaders/color_only_vs.glsl

@@ -2,12 +2,15 @@
 #version 330
 
 layout (location = 0) in vec3 a_pos;
-layout (location = 1) in vec3 a_normal;
-
+layout (location = 1) in vec3 a_color;
 
 uniform mat4 u_mvp; 
 
+out vec3 v_color;
+
+
 void main()
 {
+	v_color = a_color;
 	gl_Position = u_mvp * vec4(a_pos.xyz, 1);
 }