Mar 10
25

8. OpenGL Double Buffering

9 Comments



Last time we looked at rotation the cube looked ‘broken’ now it
looked like this because we had a single buffer running. This
means that the program is automatically drawing straight to the
window. To fix this we add a second buffer, by changing the:
glutInitDisplayMode (GLUT_SINGLE);
to:
glutInitDisplayMode (GLUT_DOUBLE);
this is giving the programa buffer to draw what it has to, then transfer
what is acctually needed to the screen.
You may notice that alot of games these days even have a triple
buffer, this is pretty redundant in OpenGL, in fact it doesn’t even exist in OpenGL.

When changing the buffer from Single to Double we also have to
tell the program to swap the buffers, so we acctually see what
is on the second, and not just what we saw before.

To do this, change the line in the ‘display’ function that says:
glFlush();
to:
glutSwapBuffers();

And your done, the cube should be rotating perfectly.

If you have any questions, please email me at swiftless@gmail.com

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47. 		    #include <GL/gl.h>
#include <GL/glut.h>

GLfloat angle = 0.0; //set the angle of rotation

void cube (void) {
    glRotatef(angle, 1.0, 0.0, 0.0); //rotate on the x axis
    glRotatef(angle, 0.0, 1.0, 0.0); //rotate on the y axis
    glRotatef(angle, 0.0, 0.0, 1.0); //rotate on the z axis
    glColor3f(1.0, 0.0, 0.0);
    glutWireCube(2);
}

void display (void) {
    glClearColor (0.0,0.0,0.0,1.0);
    glClear (GL_COLOR_BUFFER_BIT);
    glLoadIdentity();  
    gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
    cube();
    glutSwapBuffers();
    angle ++;
}

void reshape (int w, int h) {
    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) {
    glutInit (&argc, argv);
    glutInitDisplayMode (GLUT_DOUBLE); //set up the double 
buffering
    glutInitWindowSize (500, 500);
    glutInitWindowPosition (100, 100);
    glutCreateWindow (“A basic OpenGL Window“);
    glutDisplayFunc (display);
    glutIdleFunc (display);
    glutReshapeFunc (reshape);
    glutMainLoop ();
    return 0;
}

Related posts:

  1. 6. OpenGL Cube (Version 2.0)
  2. 36. OpenGL Framebuffers
  3. 10. OpenGL Scaling
  4. 9. OpenGL Blending
  5. 7. OpenGL Rotation and Translation (Version 2.0)

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This entry was posted on March 25, 2010 at 4:13 am. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

Posted in OpenGL by Swiftless 9 Comments

9 Responses to "8. OpenGL Double Buffering"

  • oldnewbie says:
    March 13, 2011 at 8:24 am
    Reply

    I wish there was an explanation for glulookat.

  • Dhiraj says:
    February 23, 2011 at 4:10 pm
    Reply

    Hi the code works with glew.h
    and not gl.h

  • prabhakar says:
    October 27, 2010 at 2:45 pm
    Reply

    its better if u have given syntax for gluLookT

    Syntax

    Copy
    void WINAPI gluLookAt(
    GLdouble eyex,
    GLdouble eyey,
    GLdouble eyez,
    GLdouble centerx,
    GLdouble centery,
    GLdouble centerz,
    GLdouble upx,
    GLdouble upy,
    GLdouble upz
    );

    eyex
    The position of the eye point.

    eyey
    The position of the eye point.

    eyez
    The position of the eye point.

    centerx
    The position of the reference point.

    centery
    The position of the reference point.

    centerz
    The position of the reference point.

    upx
    The direction of the up vector.

    upy
    The direction of the up vector.

    upz
    The direction of the up vector.

    Return Value

    This function does not return a value.

  • Mark says:
    September 26, 2010 at 11:12 am
    Reply

    A note for those following along on a Linux box. This code will produce an error that looks like:
    error: stray ‘\342’ in program
    To fix this replace the angled quotes in the program ie: “” with vertical quotes. Just a simple copy and paste thing.

  • Imrn says:
    July 26, 2010 at 3:30 am
    Reply

    very easy to understand..can you please add something about the lookAt method? it has got lot of parameters, what do they stand for?

    thanks

  • SiUnit says:
    June 24, 2010 at 6:17 am
    Reply

    I agree with Khalladay, its great to see well explained, easy to follow tutorials. Thanks!

  • Khalladay says:
    May 15, 2010 at 9:03 pm
    Reply

    These tutorials have been awesome. Props for posting an OpenGL tutorial thats actually useful and geared to absolute beginners.

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