PREGUNTAS

ESCRIBA A MANERA DE REPORTE QUE  HACE  GLUTLOOKAT

Esta es la función que determina dónde y cómo está dispuesta la cámara. Cuidado que la posición de la cámara no tiene nada que ver con el tipo de proyección que hayamos definido. La proyección se define sólo una vez.

¿EN EL CÓDIGO HAGA  REFLEXION  SOBRE GLTRANSLATEF Y GLUTAT ()?
La función GLTRASLATE se utiliza para mover de un punto a otro un objeto y la función GLUTAT se usa para visualizar el objeto.

¿SE COMPORTAN DE LA MISMA MANERA?

No se comportan de la misma manera puesto que uno mueve el objeto y el otro mueve la cámara para visualizar el objeto.

PERO EN REALIDAD NO SON EXACTAMENTE LO MISMO, DEDUZCA  QUE DIFERENCIA EXISTE EN EL PROGRAMA

CODIGO 

#include <GL/glut.h> // Once you include glut.h (you don't need gl.h or glu.h) 

GLfloat X = 0.0f; // Translate screen to x direction (left or right)
GLfloat Y = 0.0f; // Translate screen to y direction (up or down)
GLfloat Z = 0.0f; // Translate screen to z direction (zoom in or out)
GLfloat rotX = 0.0f; // Rotate screen on x axis
GLfloat rotY = 0.0f; // Rotate screen on y axis
GLfloat rotZ = 0.0f; // Rotate screen on z axis
GLfloat rotLx = 0.0f; // Translate screen by using the glulookAt function (left or right)
GLfloat rotLy = 0.0f; // Translate screen by using the glulookAt function (up or down)
GLfloat rotLz = 0.0f; // Translate screen by using the glulookAt function (zoom in or out)
void glDisplayLines(void); // Did declare the function    // so I did not have to check for order of the functions
// Initialize the OpenGL window

void init(void)
{
    glClearColor (0.0, 0.0, 0.0, 0.0); // Clear the color
   glShadeModel (GL_FLAT); // Set the shading model to GL_FLAT
   glEnable (GL_LINE_SMOOTH);
    glHint(GL_LINE_SMOOTH_HINT, GL_NICEST); // Set Line Antialiasing}
// Draw the lines (x,y,z)
void display(void)
{
    glClear (GL_COLOR_BUFFER_BIT); // Clear the Color Buffer 
 glPushMatrix();  // It is important to push the Matrix before calling    // glRotatef and glTranslatef    glRotatef(rotX,1.0,0.0,0.0); // Rotate on x
  glRotatef(rotY,0.0,1.0,0.0); // Rotate on y
 glRotatef(rotZ,0.0,0.0,1.0); // Rotate on z
 glTranslatef(X, Y, Z);  // Translates the screen left or right,    // up or down or zoom in zoom out
    // Draw the positive side of the lines x,y,z
    glBegin(GL_LINES);
    glColor3f (0.0, 1.0, 0.0); // Green for x axis
    glVertex3f(0,0,0);
    glVertex3f(10,0,0);
    glColor3f(1.0,0.0,0.0); // Red for y axis  
    glVertex3f(0,0,0);
    glVertex3f(0,10,0);
    glColor3f(0.0,0.0,1.0); // Blue for z axis  
    glVertex3f(0,0,0);
    glVertex3f(0,0,10);
    glEnd();
    // Dotted lines for the negative sides of x,y,z  
glEnable(GL_LINE_STIPPLE);  // Enable line stipple to use a
    // dotted pattern for the lines
 glLineStipple(1, 0x0101);  // Dotted stipple pattern for the lines
  glBegin(GL_LINES);
    glColor3f (0.0, 1.0, 0.0);  // Green for x axis
    glVertex3f(-10,0,0);
    glVertex3f(0,0,0);
    glColor3f(1.0,0.0,0.0);  // Red for y axis
    glVertex3f(0,0,0);
    glVertex3f(0,-10,0);
    glColor3f(0.0,0.0,1.0);  // Blue for z axis  
    glVertex3f(0,0,0);
    glVertex3f(0,0,-10);
    glEnd();
    glDisable(GL_LINE_STIPPLE);  // Disable the line stipple
    glPopMatrix();   // Don't forget to pop the Matrix  
    glutSwapBuffers();
}
// This function is called whenever the window size is changed
void reshape (int w, int h)
{
    glViewport (0, 0, (GLsizei) w, (GLsizei) h); // Set the viewport
    glMatrixMode (GL_PROJECTION);  // Set the Matrix mode
    glLoadIdentity ();
    gluPerspective(75, (GLfloat) w /(GLfloat) h , 0.10, 100.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt (rotLx, rotLy, 15.0 + rotLz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
}
// This function is used for the navigation keys
void keyboard (unsigned char key, int x, int y)
{
switch (key) {   // x,X,y,Y,z,Z uses the glRotatef() function
    case 'x': // Rotates screen on x axis
    rotX -= 0.5f;
    break;    case 'X': // Opposite way
    rotX += 0.5f;
    break;    case 'y': // Rotates screen on y axis
    rotY -= 0.5f;
    break;    case 'Y': // Opposite way
    rotY += 0.5f;
    break;
    case 'z': // Rotates screen on z axis
    rotZ -= 0.5f;
    break;    case 'Z': // Opposite way
    rotZ += 0.5f;
    break;
    // j,J,k,K,l,L uses the gluLookAt function for navigation   

    case 'j':
    rotLx -= 0.2f;
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt (rotLx, rotLy, 15.0 + rotLz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
    break;    case 'J':
    rotLx += 0.2f;
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt (rotLx, rotLy, 15.0 + rotLz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
    break;
    case 'k':
    rotLy -= 0.2f;
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt (rotLx, rotLy, 15.0 + rotLz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
    break;    case 'K':
    rotLy += 0.2f;
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt (rotLx, rotLy, 15.0 + rotLz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
    break;    case 'l':  // It has a special case when the rotLZ becomes
  // less than -15 the screen is viewed from the opposite side
    // therefore this if statement below does not allow rotLz be less than -15  
if(rotLz + 14 >= 0)
    rotLz -= 0.2f;         
    glMatrixMode(GL_MODELVIEW);  
    glLoadIdentity();
    gluLookAt (rotLx, rotLy, 15.0 + rotLz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
    break;    case 'L':
    rotLz += 0.2f;
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt (rotLx, rotLy, 15.0 + rotLz, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
    break;    case 'b': // Rotates on x axis by -90 degree
    rotX -= 90.0f;
    break;    case 'B': // Rotates on y axis by 90 degree
    rotX += 90.0f;
    break;    case 'n': // Rotates on y axis by -90 degree
    rotY -= 90.0f;
    break;    case 'N': // Rotates on y axis by 90 degree
    rotY += 90.0f;
    break;    case 'm': // Rotates on z axis by -90 degree
    rotZ -= 90.0f;
    break;
    case 'M': // Rotates on z axis by 90 degree
    rotZ += 90.0f;
    break;    case 'o': // Default, resets the translations vies from starting view
    case 'O':
    X = Y = 0.0f;
    Z = 0.0f;
    rotX = 0.0f;
    rotY = 0.0f;
    rotZ = 0.0f;
    rotLx = 0.0f;
    rotLy = 0.0f;
    rotLz = 0.0f;
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(rotLx, rotLy, 15.0f + rotLz, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f);
    break;}
    glutPostRedisplay(); // Redraw the scene
}
// called on special key pressed
void specialKey(int key, int x, int y) {
// The keys below are using the gluLookAt() function for navigation
// Check which key is pressed
switch(key) {
    case GLUT_KEY_LEFT : // Rotate on x axis
    X -= 0.1f;
    break;
    case GLUT_KEY_RIGHT : // Rotate on x axis (opposite)
    X += 0.1f;
    break;
    case GLUT_KEY_UP : // Rotate on y axis
    Y += 0.1f;
    break;
    case GLUT_KEY_DOWN : // Rotate on y axis (opposite)
    Y -= 0.1f;
    break;
    case GLUT_KEY_PAGE_UP: // Rotate on z axis
    Z -= 0.1f;
    break;
    case GLUT_KEY_PAGE_DOWN: // Rotate on z axis (opposite)
    Z += 0.1f;
    break;
}
    glutPostRedisplay(); // Redraw the scene
}
// Main entry point of the program
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);  // Setup display mode to
      // double buffer and RGB color
    glutInitWindowSize (600,600); // Set the screen size
    glutCreateWindow("OpenGL 3D Navigation Program");
    init ();
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutKeyboardFunc(keyboard); // set window's key callback
    glutSpecialFunc(specialKey); // set window's to specialKey callback
    glutMainLoop();
    return 0;
}   

RESULTADO DE LA EJECUCION DEL CODIGO