OpenGL - Window, Camera, Scene (bme2dsysr.ppt)

// http://cg.iit.bme.hu/portal/oktatott-targyak/szamitogepes-grafika-es-kepfeldolgozas/2d-grafikus-rendszerek
// http://cg.iit.bme.hu/portal/sites/default/files/oktatott-targyak/szamitogepes-grafika-es-kepfeldolgozas/2d-grafikus-rendszerek/bme2dsysr.ppt
// 12. diától 21. diáig részletek

Window window;
int appWinHeight, appWinWidth;

// ...

void MouseDown(int button, int state, int x, int y) {
  if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    window.MouseLD(x, appWinHeight - y); // Windows kr.
  glutPostRedisplay();
}

// ...

struct Window {
  Scene scene;
  // ...

  void MouseLD(int X, int Y) {
    // ...
    scene.InputPipe(X, Y);
    // ...
  }
}

class Camera {
  Rect viewport, window;

  void SetGL() {
    glViewport(viewport.left, viewport.bottom,
        viewport.width, viewport.height);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(window.left, window.left + window.width,
        window.bottom, window.bottom + window.height);
  }

  Vector Inverse(Vector scrPos) {
    float sx = window.width / viewport.width;
    float sy = window.height / viewport.height;
    return Vector(
        (scrPos.x – viewport.left) * sx + window.left,
        (scrPos.y – viewport.bottom) * sy + window.bottom
        );
  }
};

class Scene {
  // ...
  Camera camera;
  // ...

  void InputPipe(int X, int Y) {
    Vector wPos = camera.Inverse(Vector(X, Y));
    // ...
  }
}