Add debug info in the top left corner.

src/camera.cpp

@@ -21,6 +21,24 @@ static void handleMouseMove(int x, int y)
     glutPostRedisplay();
 }
 
+static float getFPS()
+{
+    static int frames = 0;
+    static float fps = 0;
+    static auto timeBase = glutGet(GLUT_ELAPSED_TIME);
+
+    ++frames;
+    const auto time = glutGet(GLUT_ELAPSED_TIME);
+    if (time - timeBase > 2000) {
+        fps = frames * 1000.0f / (time - timeBase);
+        frames = 0;
+        timeBase = time;
+    }
+
+
+    return fps;
+}
+
 static void move(unsigned char key)
 {
     float speed = 0.5;
@@ -80,6 +98,7 @@ std::string Camera::infoLine()
     stringstream buffer;
     buffer << "Pos(x,y,z) = (" << pos[0] << ", " << pos[1] << ", " << pos[2] << ")\n";
     buffer << "Angle(p,y) = (" << angle[0] << ", " << angle[1] << ")\n";
+    buffer << "FPS = " << getFPS() << "\n";
     return buffer.str();
 }
 

src/glutils.cpp

@@ -83,12 +83,17 @@ void fmri::changeWindowSize(int w, int h)
     glMatrixMode(GL_MODELVIEW);
 }
 
-void fmri::renderText(std::string_view text)
+void fmri::renderText(std::string_view text, int x, int y)
 {
     constexpr auto font = GLUT_BITMAP_HELVETICA_10;
-    glRasterPos2i(0, 0);
+    glRasterPos2i(x, y);
     for (char c : text) {
-        glutBitmapCharacter(font, c);
+        if (c == '\n') {
+            y += 12;
+            glRasterPos2i(x, y);
+        } else {
+            glutBitmapCharacter(font, c);
+        }
     }
 }
 
@@ -117,3 +122,32 @@ void fmri::throttleIdleFunc()
 
     lastCalled = now;
 }
+
+void fmri::restorePerspectiveProjection() {
+
+    glMatrixMode(GL_PROJECTION);
+    // restore previous projection matrix
+    glPopMatrix();
+
+    // get back to modelview mode
+    glMatrixMode(GL_MODELVIEW);
+}
+
+void fmri::setOrthographicProjection() {
+
+    // switch to projection mode
+    glMatrixMode(GL_PROJECTION);
+
+    // save previous matrix which contains the
+    //settings for the perspective projection
+    glPushMatrix();
+
+    // reset matrix
+    glLoadIdentity();
+
+    // set a 2D orthographic projection
+    gluOrtho2D(0, glutGet(GLUT_WINDOW_WIDTH), glutGet(GLUT_WINDOW_HEIGHT), 0);
+
+    // switch back to modelview mode
+    glMatrixMode(GL_MODELVIEW);
+}

src/glutils.hpp

@@ -34,7 +34,7 @@ namespace fmri {
      *
      * @param text The text to draw.
      */
-    void renderText(std::string_view text);
+    void renderText(std::string_view text, int x = 0, int y = 0);
 
     /**
      * Check if there are OpenGL errors and report them.
@@ -45,4 +45,8 @@ namespace fmri {
      * Slow down until the idle func is being called a reasonable amount of times.
      */
     void throttleIdleFunc();
+
+    void setOrthographicProjection();
+
+    void restorePerspectiveProjection();
 }

src/main.cpp

@@ -63,6 +63,15 @@ static void loadSimulationData(const Options &options)
 
 static void renderLayerName(const LayerData &data);
 
+static void renderDebugInfo()
+{
+    glLoadIdentity();
+    setOrthographicProjection();
+    glColor3f(1, 1, 0);
+    renderText(Camera::instance().infoLine(), 2, 10);
+    restorePerspectiveProjection();
+}
+
 static void render()
 {
     // Clear Color and Depth Buffers
@@ -92,6 +101,8 @@ static void render()
 
     glPopMatrix();
 
+    renderDebugInfo();
+
     glutSwapBuffers();
 }