separated rendering and imgui

src/apps/MeshProcessingViewer.cpp

@@ -35,6 +35,8 @@
 #include <pmp/algorithms/SurfaceSimplification.h>
 #include <pmp/algorithms/SurfaceRemeshing.h>
 
+#include <imgui.h>
+
 using namespace pmp;
 
 //=============================================================================
@@ -110,3 +112,56 @@ void MeshProcessingViewer::keyboard(GLFWwindow* window, int key, int scancode, i
         }
     }
 }
+
+//----------------------------------------------------------------------------
+
+void MeshProcessingViewer::processImGUI()
+{
+    MeshViewer::processImGUI();
+
+#ifndef __EMSCRIPTEN__
+    ImGui::SetNextWindowSize(ImVec2(0,0));
+#endif
+    ImGui::Begin("Mesh Processing");
+
+    if (ImGui::Button("Decimate"))
+    {
+        SurfaceSimplification ss(m_mesh);
+        ss.initialize(5); // aspect ratio
+        ss.simplify(m_mesh.nVertices() * 0.1);
+        updateMesh();
+    }
+
+    if (ImGui::Button("Subdivision"))
+    {
+        if (m_mesh.isTriangleMesh())
+            SurfaceSubdivision(m_mesh).loop();
+        else
+            SurfaceSubdivision(m_mesh).catmullClark();
+        updateMesh();
+    }
+
+    if (ImGui::Button("Adaptive Remeshing"))
+    {
+        auto bb = m_mesh.bounds().size();
+        SurfaceRemeshing(m_mesh).adaptiveRemeshing(
+                0.001 * bb,  // min length
+                1.0 * bb,    // max length
+                0.001 * bb); // approx. error
+        updateMesh();
+    }
+
+    if (ImGui::Button("Uniform Remeshing"))
+    {
+        Scalar l(0);
+        for (auto eit : m_mesh.edges())
+            l += distance(m_mesh.position(m_mesh.vertex(eit, 0)),
+                    m_mesh.position(m_mesh.vertex(eit, 1)));
+        l /= (Scalar)m_mesh.nEdges();
+        SurfaceRemeshing(m_mesh).uniformRemeshing(l);
+        updateMesh();
+    }
+
+    ImGui::End();
+}
+

src/apps/MeshProcessingViewer.h

@@ -47,7 +47,10 @@ class MeshProcessingViewer : public pmp::MeshViewer
 protected:
     //! this function handles keyboard events
     void keyboard(GLFWwindow* window, int key, int scancode,
-                  int action, int mod);
+                  int action, int mod) override;
+
+    //! draw the scene in different draw modes
+    virtual void processImGUI() override;
 };
 
 //=============================================================================

src/pmp/gl/MeshViewer.cpp

@@ -97,29 +97,35 @@ void MeshViewer::updateMesh()
 
 //-----------------------------------------------------------------------------
 
-void MeshViewer::draw(const std::string& drawMode)
+void MeshViewer::processImGUI()
 {
-    // uncomment next line to showcase imgui!
-    //ImGui::ShowTestWindow();
-    //ImGui::ShowStyleEditor();
-
-    // draw GUI
     ImGui::SetNextWindowPos(ImVec2(10,10));
-#ifndef __EMSCRIPTEN__
+#ifndef __EMSCRIPTEN__ // this does not work in emscripten
     ImGui::SetNextWindowSize(ImVec2(0,0));
 #endif
     ImGui::Begin("Mesh Info");
-    ImGui::Text("#vertices: %d", (int)m_mesh.nVertices());
-    ImGui::Text("#faces:    %d", (int)m_mesh.nFaces());
+
+    // output mesh statistics
+    ImGui::BulletText("%d vertices", (int)m_mesh.nVertices());
+    ImGui::BulletText("%d edges", (int)m_mesh.nEdges());
+    ImGui::BulletText("%d faces", (int)m_mesh.nFaces());
+
+    // control crease angle
     ImGui::PushItemWidth(100);
     ImGui::SliderFloat("Crease Angle", &m_creaseAngle, 0.0f, 180.0f, "%.0f");
     ImGui::PopItemWidth();
     if (m_creaseAngle != m_mesh.creaseAngle())
     {
         m_mesh.setCreaseAngle(m_creaseAngle);
     }
+
     ImGui::End();
+}
 
+//-----------------------------------------------------------------------------
+
+void MeshViewer::draw(const std::string& drawMode)
+{
     // draw mesh
     m_mesh.draw(m_projectionMatrix, m_modelviewMatrix, drawMode);
 }

src/pmp/gl/MeshViewer.h

@@ -62,11 +62,14 @@ class MeshViewer : public TrackballViewer
     virtual void updateMesh();
 
     //! draw the scene in different draw modes
-    virtual void draw(const std::string& _draw_mode);
+    virtual void draw(const std::string& _draw_mode) override;
+
+    //! handle ImGUI interface
+    virtual void processImGUI() override;
 
     //! this function handles keyboard events
-    void keyboard(GLFWwindow* window, int key, int scancode,
-                  int action, int mod);
+    virtual void keyboard(GLFWwindow* window, int key, int scancode,
+                          int action, int mod) override;
 
 protected:
     SurfaceMeshGL m_mesh; //!< the mesh

src/pmp/gl/Window.cpp

@@ -116,13 +116,12 @@ Window::Window(const char* title, int width, int height)
     glfwSetFramebufferSizeCallback(m_window, glfwResize);
 
     // setup imgui
-    init_gui();
+    initImGUI();
 }
 
 //-----------------------------------------------------------------------------
 
-
-void Window::init_gui()
+void Window::initImGUI()
 {
     ImGui_Init(m_window, false);
 
@@ -188,7 +187,6 @@ void Window::init_gui()
     style.Colors[ImGuiCol_ModalWindowDarkening]  = ImVec4(0.20f, 0.20f, 0.20f, 0.35f);
 }
 
-
 //-----------------------------------------------------------------------------
 
 Window::~Window()
@@ -205,41 +203,22 @@ Window::~Window()
 int Window::run()
 {
 #if __EMSCRIPTEN__
-    emscripten_set_main_loop(Window::emscripten_render_loop, 0, 1);
+    emscripten_set_main_loop(Window::render_frame, 0, 1);
 #else
     while (!glfwWindowShouldClose(m_window))
     {
-        // prepare GUI
-        ImGui_NewFrame();
-
-        // draw scene
-        display();
-
-        // draw GUI
-        ImGui::Render();
-
-        // swap buffers
-        glfwSwapBuffers(m_window);
-
-        // handle events
-        //glfwPollEvents();
-        glfwWaitEvents();
+        Window::render_frame();
     }
 #endif
-
     glfwDestroyWindow(m_window);
-
     return EXIT_SUCCESS;
 }
 
-
 //-----------------------------------------------------------------------------
 
-
-#if __EMSCRIPTEN__
-
-void Window::emscripten_render_loop()
+void Window::render_frame()
 {
+#if __EMSCRIPTEN__
     // determine correct canvas/framebuffer size
     int w, h, f;
     double dw, dh;
@@ -251,9 +230,11 @@ void Window::emscripten_render_loop()
         emscripten_set_canvas_size(w, h);
         glfwResize(m_instance->m_window, w, h);;
     }
+#endif
 
-    // prepare GUI
+    // preapre and process ImGUI elements
     ImGui_NewFrame();
+    m_instance->processImGUI();
 
     // draw scene
     m_instance->display();
@@ -265,12 +246,10 @@ void Window::emscripten_render_loop()
     glfwSwapBuffers(m_instance->m_window);
 
     // handle events
-    glfwPollEvents();
+    glfwWaitEvents();
+    //glfwPollEvents();
 }
 
-#endif
-
-
 //-----------------------------------------------------------------------------
 
 void Window::glfwError(int error, const char* description)

src/pmp/gl/Window.h

@@ -63,9 +63,7 @@ class Window
     static void glfwScroll(GLFWwindow* window, double xoffset, double yoffset);
     static void glfwResize(GLFWwindow* window, int width, int height);
 
-#if __EMSCRIPTEN__
-    static void emscripten_render_loop();
-#endif
+    static void render_frame();
 
     static Window* m_instance;
 
@@ -89,9 +87,12 @@ class Window
     //! this function is called if the window is resized
     virtual void resize(GLFWwindow* window, int width, int height) = 0;
 
+    //! this function renders the ImGUI elements and handles their events
+    virtual void processImGUI() {}
+
 protected:
-    //! setup imgui style
-    void init_gui();
+    //! setup ImGUI user interface
+    void initImGUI();
 
 protected:
     //! GLFW window pointer