dlivingstone · July 6, 2012 22:18 · Jul 6, 2012
diff --git a/main.cpp b/main.cpp
@@ -0,0 +1,196 @@
+// main.cpp
+// A very basic OpenGL/GLUT application using the deprecated OpenGL 1.x
+
+// (c) Daniel Livingstone, 2012
+
+// The structure of this program is typical of many simple OpenGL demonstration
+// programs, but is unsuitable for larger projects: The very basic structure
+// is useful when learning OpenGL, but very poor for building large, complex
+// systems such as modern games
+
+// In this 'game' the player has to move (using w,s,a,d keys) and resize (using
+// arrow keys) a white cursor to surround a red target as tightly as possible.
+// When the player succeeds, the red target will be randomly resized and positioned
+
+
+// Many to-do's in this project:
+// - Seperate update from keyboard and render functions
+// - - Fix keyboard to recognise multiple key presses
+// - Use timers to provide better control over frame-rate
+// - - Try GLUT timers first
+// - - Then frame limiter
+// - - Then independent physics/render loop
+// - Introduce game-state, with main menu and 'game' and pause screens
+
+#define FREEGLUT_STATIC
+#include <GL/freeglut.h>
+
+// C stdlib and C time libraries for rand and time functions
+#include <cstdlib>
+#include <ctime>
+
+// iostream for cin and cout
+#include <iostream>
+
+// stringstream and string
+#include <sstream>
+#include <string>
+
+
+float xpos = 0.0f;
+float ypos = 0.0f;
+float xsize = 0.25f;
+float ysize = 0.25f;
+
+float targetXPos = 0.0f;
+float targetYPos = 0.0f;
+float targetXSize = 0.0f;
+float targetYSize = 0.0f;
+
+int score = 0;
+
+clock_t lastTime; // clock_t is an integer type
+clock_t currentTime; // use this to trace time between frames
+
+void displayString(float x, float y, void* font, const char *str)
+{
+	glRasterPos2f(x, y);
+	while (*str != NULL)
+		glutBitmapCharacter(font, *str++);
+}
+
+
+void init(void) 
+{
+   glClearColor(0.0, 0.0, 0.0, 0.0); // set background colour
+
+   std::srand( std::time(NULL) );
+   targetXPos = (float)rand()/RAND_MAX - 0.75f;
+   targetYPos = (float)rand()/RAND_MAX - 0.75f;
+   targetXSize = 0.19f;
+   targetYSize= 0.19f;
+   lastTime = clock();
+}
+
+
+void render(void) {
+  glClear(GL_COLOR_BUFFER_BIT); // Clear all pixels
+  // drawing code goes in here!
+
+  // draw player
+  glColor3f(1.0,1.0,1.0);
+  glBegin(GL_POLYGON);
+      glVertex3f (xpos, ypos, 0.0); // first corner
+      glVertex3f (xpos+xsize, ypos, 0.0); // second corner
+      glVertex3f (xpos+xsize, ypos+ysize, 0.0); // third corner
+      glVertex3f (xpos, ypos+ysize, 0.0); // fourth corner
+  glEnd();
+  displayString(xpos+(xsize/2.0f), ypos+ysize, GLUT_BITMAP_TIMES_ROMAN_10, "Player");
+
+  // draw target
+  glColor3f(1.0,0.0,0.0);
+  glBegin(GL_POLYGON);
+      glVertex3f (targetXPos, targetYPos, 0.0); // first corner
+      glVertex3f (targetXPos+targetXSize, targetYPos, 0.0); // second corner
+      glVertex3f (targetXPos+targetXSize, targetYPos+targetYSize, 0.0); // third corner
+      glVertex3f (targetXPos, targetYPos+targetYSize, 0.0); // fourth corner
+  glEnd();
+  displayString(targetXPos+(targetXSize/2.0f), targetYPos+targetYSize, GLUT_BITMAP_TIMES_ROMAN_10, "Target");
+
+  if ( (targetXPos >= xpos) && (targetXPos+targetXSize <= xpos+xsize)	// cursor surrounds target in x
+	  && (targetYPos >= ypos) && (targetYPos+targetYSize <= ypos+ysize) // cursor surrounds target in y
+	  && ( xsize <= targetXSize+0.1f) && ( ysize <= targetYSize+0.1f) ) // cursor only slightly larger than target
+  {
+	  // congrats, player has scored!
+	  score += 100;
+	  std::cout << "Score: " << score << std::endl;
+
+	  // randomize target
+	  targetXPos = (float)rand()/RAND_MAX - 0.75f;
+	  targetYPos = (float)rand()/RAND_MAX - 0.75f;
+      targetXSize = (float)rand()/RAND_MAX * 0.8f;
+      targetYSize= (float)rand()/RAND_MAX * 0.8f;
+  }
+
+  // Calculate ms/frame
+  // Some OpenGL drivers will limit the frames to 60fps (16.66 ms/frame)
+  // If so, expect to see the time to rapidly switch between 16 and 17...
+  glColor3f(1.0,1.0,1.0);
+  currentTime = clock();
+  // On some systems, CLOCKS_PER_SECOND is 1000, which makes the arithmetic below redundant
+  // - but this is not necessarily the case on all systems
+  float milliSecondsPerFrame = ((currentTime - lastTime)/(float)CLOCKS_PER_SEC*1000);
+
+  // Print out the score and frame time information
+  std::stringstream strStream;
+  strStream << "Score:" << score;
+  strStream << "          ms/frame: " << milliSecondsPerFrame;
+  displayString(-0.9,0.9, GLUT_BITMAP_9_BY_15, strStream.str().c_str());
+  lastTime = clock();
+
+  glutSwapBuffers();  // Redraw (double buffered)
+}
+
+void keyboard(unsigned char key, int x, int y)
+{
+	switch (key) {
+	case 'w':
+	case 'W': 
+		ypos += 0.05;
+		break;
+	case 's': 
+	case 'S':
+		ypos -= 0.05;
+		break;
+	case 'a': 
+	case 'A': 
+		xpos -= 0.05;
+		break;
+	case 'd': 
+	case 'D':
+		xpos += 0.05;
+		break;
+	}
+
+	glutPostRedisplay();
+}
+
+void specialKeys(int key, int x, int y)
+{
+	switch (key) {
+	case GLUT_KEY_UP: 
+		ysize += 0.05;
+		break;
+	case GLUT_KEY_DOWN:
+		ysize -= 0.05;
+		break;
+	case GLUT_KEY_LEFT: 
+		xsize -= 0.05;
+		break;
+	case GLUT_KEY_RIGHT:
+		xsize += 0.05;
+		break;
+	}
+
+	glutPostRedisplay();
+}
+
+
+int main(int argc, char **argv) 
+{
+  glutInit(&argc, argv);
+  glutInitWindowPosition(100,100);
+  glutInitWindowSize(400,400 );
+  glutInitDisplayMode(GLUT_DOUBLE); 
+  glutCreateWindow("Demo Project");
+  init();
+
+  glutDisplayFunc(render); // Register the render callack
+  glutKeyboardFunc(keyboard); // Setup keyboard callback
+  glutSpecialFunc(specialKeys); // Setup special keys callback
+  glutIdleFunc(render); // Set idle callback to the render function
+  glutMainLoop();	// loop while waiting for messages
+				// by default, window will respond
+				// to resize, move and close events
+  return 0;	// return 0 indicates program exited OK
+}