Jump to content
  • Advertisement
Sign in to follow this  

[SOLVED] trouble with glGenTexture and changing textures

This topic is 3461 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

I had this working once before, but now I cannot seem to get it working and it's driving me nuts. A second set of eyes may see what I can't. Every time I run the program the message "texture ID == NULL" shows, and I get a white texture. I have no idea why it is becoming NULL, as I am creating the texture, then changing the RGB values to it, along with the mipmap. So yea if anyone can figure out why I keep getting a blank white image it would be greatly appreciated.
[source lang=cpp]
int main(int argc, char** argv)
    char FilePath[25];

    printf("Enter file name: ");
    cin>> FilePath;
    /*InitAVI(FilePath, pGetFrame, iWidth, iHeight, FirstFrame, TotalFrames);
    if(pGetFrame == NULL){
        printf("Error: pGetFrame returned NULL\n");
        return 0;
    printf("Width: %i\nHeight: %i\nTotal Frames: %i\n", iWidth, iHeight, TotalFrames);*/
    glEnable (GL_TEXTURE_2D); /* enable texture mapping */
    //glEnable (GL_DEPTH_TEST);
    //glPolygonMode (GL_FRONT_AND_BACK, GL_FILL);
    if(GetLastError() == GL_INVALID_VALUE || GetLastError() == GL_INVALID_OPERATION) printf("Error: cannot create texture\n");

    //int histR[256], histG[256], histB[256];
    GetBMPDimensions(FilePath, g_Width, g_Height);
    rgb = new byte[g_Width*g_Height*3];
    grey = new byte[g_Width*g_Height*3];
    if(!LoadBMPFile(FilePath, g_TexID, rgb, g_Width, g_Height)) printf("Error: cannot load image\n");
    RGBToGreyScale(rgb, grey, g_Width, g_Height);
    //CreateCumulHistogram(grey, histR, histG, histB, g_Width, g_Height, GREY_CLR);
    //NormalizeHistogram(grey, histR, histG, histB, g_Width, g_Height);
    ChangeTexture(g_TexID, grey, g_Width, g_Height);

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);
    glutInitWindowSize(g_Width, g_Height);
    glutInitWindowPosition(512 - g_Width / 2, 384 - g_Height / 2);
    glutCreateWindow("FPS: ");
    if(!glIsTexture(g_TexID)) printf("Error: texture ID == NULL\n");
    return 0;

bool ChangeTexture(GLuint TexID, byte* rgb, int iWidth, int iHeight)
    glBindTexture(GL_TEXTURE_2D, TexID); // Bind the ID texture specified by the 2nd parameter

    // Finally we define the 2d texture
    glTexImage2D(GL_TEXTURE_2D, 0, 3, iWidth, iHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, rgb);

    // And create 2d mipmaps for the minifying function
    gluBuild2DMipmaps(GL_TEXTURE_2D, 3, iWidth, iHeight, GL_RGB, GL_UNSIGNED_BYTE, rgb);

    return true;

void CreateTexture(GLuint TexID)
    glGenTextures(1, &TexID); //generate 1 texture

    glBindTexture(GL_TEXTURE_2D, TexID); // Bind the ID texture specified by the 2nd parameter

    // The next commands sets the texture parameters
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); // If the u,v coordinates overflow the range 0,1 the image is repeated
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); // The magnification function ("linear" produces better results)
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST); //The minifying function

    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE); // We don't combine the color with the original surface color, use only the texture map.

EDIT: I got it working now, i was missing some enables and initializing a window. [Edited by - scwizzo on May 28, 2009 11:32:20 PM]

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!