CODEWITHSUNDEEP
opengl
Poojan
Poojan

Reputation: 3332

My display() function only displays when it enters it the first time. Then it shows a blank window


void init(void)
{ 
    glEnable(GL_DEPTH_TEST);
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
}



void display(void)
{
    glClearColor(1.0, 1.0, 1.0, 1.0);



glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glScalef(1.0,1.0,1.0);
glColor3f(0.0,0.0,0.0);
    glBegin(GL_POLYGON);
    glVertex2f(-0.5, -0.5);
    glVertex2f(-0.5, 0.5);
    glVertex2f(0.5, 0.5);
    glVertex2f(0.5, -0.5);
glEnd();
    glutSwapBuffers();




}



void reshape(int w, int h)
{ 
    int height = h;
    int width = w;
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
    glMatrixMode(GL_MODELVIEW);
}



int main(int argc, char* argv[])
{
    Complex c(0,0);
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
    glutInitWindowSize(512, 512);
    glutInitWindowPosition(100, 100);
    winID = glutCreateWindow("Fractal");
    init();
    glutDisplayFunc(display);
    glutIdleFunc(display);
    glutReshapeFunc(reshape);
    // Compute the update rate here...
    glutMainLoop();
    return 0;
}

I get a square if I put the code in display(), except the glutSwapBuffers() in if condition which checks whether the code has entered display the first time. If I remove the if, I get a white window

Upvotes: 0

Views: 569

Answers (1)

max
max

Reputation: 4348

Put an extra glTranslatef(0.0f, 0.0f, -5.0f) in your display function, to push everything 5 units back into the scene, otherwise you wont see what you're drawing at the origin.

Btw, the line glScalef(1.0,1.0,1.0) doesn't do anything, remove it to avoid unnecessary calculations.

EDIT: There is no "eye" in OpenGL. More specifically, it is always fixed at (0,0,0) looking down at the negative z-axis. You have to move the whole scene with the inverse of the eye transformations. You can either move the scene manually so your eye can see it, or use gluLookAt, where you can specify the "eye", but in the background it just transforms the scene so the fixed "eye" can see it.

Further reading: http://www.opengl.org/archives/resources/faq/technical/viewing.htm

Upvotes: 1

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