z-fighting solved with silhouette plane

CGAL · Jun 14, 2023 · db222f0 · db222f0
1 parent 5808019
commit db222f0
Show file tree

Hide file tree

Showing 5 changed files with 36 additions and 3 deletions.
diff --git a/Arrangement_on_surface_2/demo/earth/Camera.h b/Arrangement_on_surface_2/demo/earth/Camera.h
@@ -15,6 +15,7 @@ class Camera
 
   void set_pos(const QVector3D& pos) { m_pos = pos; }
   void set_pos(float x, float y, float z) { m_pos = QVector3D(x,y,z); }
+  const QVector3D& get_pos() const { return m_pos; }
 
   void perspective(float fov, float aspect_ratio, float z_near, float z_far);
 

diff --git a/Arrangement_on_surface_2/demo/earth/Geodesic_arcs.cpp b/Arrangement_on_surface_2/demo/earth/Geodesic_arcs.cpp
@@ -76,7 +76,7 @@ Geodesic_arcs::Geodesic_arcs()
   const double error = 0.001;
   std::vector<Approximate_point_2> v;
 
-  const auto& xcv = xcvs[0];
+  const auto& xcv = xcvs[1];
   //for (const auto& xcv : xcvs)
   {
     auto oi2 = approx(xcv, error, std::back_insert_iterator(v));
@@ -155,7 +155,7 @@ void Geodesic_arcs::draw()
 {
   glBindVertexArray(m_vao);
   {
-    glDrawArrays(GL_LINES, 0, m_num_arc_points);
+    glDrawArrays(GL_LINE_STRIP, 0, m_num_arc_points);
   }
   glBindVertexArray(0);
 }
diff --git a/Arrangement_on_surface_2/demo/earth/mainwidget.cpp b/Arrangement_on_surface_2/demo/earth/mainwidget.cpp
@@ -132,6 +132,11 @@ void MainWidget::init_sp_color_only()
 }
 
 
+std::ostream& operator << (std::ostream& os, const QVector4D& v)
+{
+  os << v.x() << ", " << v.y() << ", " << v.z() << ", " << v.w();
+  return os;
+}
 
 void MainWidget::resizeGL(int w, int h)
 {
@@ -151,6 +156,8 @@ void MainWidget::paintGL()
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   // SPHERE
   {
+    glEnable(GL_DEPTH_TEST);
+
     auto& sp = m_sp_smooth;
     sp.use();
     sp.set_uniform("u_mvp", mvp);
@@ -163,12 +170,29 @@ void MainWidget::paintGL()
 
   // WORLD COORDINATE AXES &  GEODESIC ARCS
   {
+    glDisable(GL_DEPTH_TEST);
+
     auto& sp = m_sp_color_only;
     sp.use();
     sp.set_uniform("u_mvp", mvp);
+
+    // compute the cutting plane
+    auto c = m_camera.get_pos();
+    const auto d = c.length();
+    const auto r = 1.0f;
+    const auto sin_alpha = r / d;
+    const auto n = (c / d); // plane unit normal vector
+    const auto cos_beta = sin_alpha;
+    const auto p = (r * cos_beta) * n;
+    QVector4D plane(n.x(), n.y(), n.z(), -QVector3D::dotProduct(p,n));
+    std::cout << plane << std::endl;
+    sp.set_uniform("u_plane", plane);
+    glEnable(GL_DEPTH_TEST);
+    m_geodesic_arcs->draw();
 
+    glEnable(GL_DEPTH_TEST);
+    sp.set_uniform("u_plane", QVector4D(0,0,0,0));// ad-hoc
     m_world_coord_axes->draw();
-    m_geodesic_arcs->draw();
 
     sp.unuse();
   }

diff --git a/Arrangement_on_surface_2/demo/earth/shaders/color_only_fs.glsl b/Arrangement_on_surface_2/demo/earth/shaders/color_only_fs.glsl
@@ -1,11 +1,17 @@
 
 #version 330
 
+uniform vec4 u_plane;
+
 in vec3 v_color;
+in vec3 v_pos;
 out vec4 out_color;
 
 
 void main()
 {
+	if( dot(u_plane, vec4(v_pos, 1)) < 0 )
+		discard;
+
 	out_color = vec4(v_color, 1);
 }
diff --git a/Arrangement_on_surface_2/demo/earth/shaders/color_only_vs.glsl b/Arrangement_on_surface_2/demo/earth/shaders/color_only_vs.glsl
@@ -7,10 +7,12 @@ layout (location = 1) in vec3 a_color;
 uniform mat4 u_mvp; 
 
 out vec3 v_color;
+out vec3 v_pos;
 
 
 void main()
 {
 	v_color = a_color;
+	v_pos = a_pos;
 	gl_Position = u_mvp * vec4(a_pos.xyz, 1);
 }