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I don't know glut well, but I'd image that reshape would be called as part of the initialization, and it leaves the modelview matrix as the last one (Im not sure if gluLookAt switches to projection, or is working with the modelview one as well)
To fix it, push the basic projection matrix onto the stack (it isnt really needed, but whatever), and rotate and translate that. Then if you pushed it, pop it as normal, so basically you need a
glMatrixMode(GL_PROJEECTION);
where the push is in display()
To keep track of the absolute coord. you're at you'll also need to use a vector or trig when you move with the keyboard function. Just switching the glTranslate() and glRotate() in the above code will work out fine until you move and then turn and then try to move forward again.
Since you're moving the camera, you want to go in the opposite direction you're actually moving. If you step forward one unit, a coordinate that was one unit from the origin should now be on it, so it needs to be translated -1 unit back so that the translated coordinate is on the origin.
Alternately, You might want to use gluLookAt() to set up the camera. the glu functions just call a string of gl functions, but it makes it a little more obvious in your code that you're moving the camera.
#include
#include
GLfloat objectx = 0.0;
GLfloat objecty = 0.0;
GLfloat objectz = -5.0;
GLint rotation = 0;
GLint motionx = 250;
GLint motiony = 250;
void init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glShadeModel(GL_FLAT);
}
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0, 1.0, 1.0);
glPushMatrix();
glRotatef((GLfloat) rotation, 0.0, 1.0, 0.0);
glTranslatef(objectx, objecty, objectz);
glutWireCube(1.0);
glPopMatrix();
glutSwapBuffers();
}
void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0, (GLfloat) w/ (GLfloat) h, 1.0, 20.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0.0, 0.0, 0.0, 0.0, 0.0, -5.0, 0.0, 1.0, 0.0);
}
void keyboard(unsigned char key, int x, int y)
{
switch (key)
{
case 'i':
objectz += 0.1;
glutPostRedisplay();
break;
case 'k':
objectz -= 0.1;
glutPostRedisplay();
break;
case 'j':
objectx += 0.1;
glutPostRedisplay();
break;
case 'o':
objectx -= 0.1;
glutPostRedisplay();
break;
default:
break;
}
}
void motion(int x, int y)
{
if (motionx > x)
rotation = (rotation - 1) % 360;
if (motionx < x)
rotation = (rotation + 1) % 360;
glutPostRedisplay();
motionx = x;
motiony = y;
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
glutCreateWindow(argv[0]);
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutMotionFunc(motion);
glutMainLoop();
return 0;
}
I bought the book Opengl Superbible : The Complete Guide to Opengl Programming for Windows Nt and Windows 95. The examples on the CD are very good and the book is really worth to get bought.
VirtualNext
