Es una función de opengl que puede alterar la matriz GL_MODELBVIEW encargada de guardar el estado de todo el sistema en cuanto a transformaciones.
Parámetros:
luLookAt(eyeX, eyeY, eyeZ, atX, atY, atZ, upX, upY, upZ)
Sirve para las trasformaciones de vista con los parámetros vistos anteriormente.PROGRAMA
#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;
}
