Question

I’m trying to generate textures like so:

#define checkImageWidth 64
#define checkImageHeight 64
static GLubyte checkImage[checkImageHeight][checkImageWidth][4];
static GLubyte otherImage[checkImageHeight][checkImageWidth][4];

static GLuint texName[2];

void makeCheckImages(void)
{
    int i, j, c;

    for (i = 0; i < checkImageHeight; i++) {
        for (j = 0; j < checkImageWidth; j++) {
            c = ((((i&0x8)==0)^((j&0x8))==0))*255;
            checkImage[i][j][0] = (GLubyte) c;
            checkImage[i][j][1] = (GLubyte) c;
            checkImage[i][j][2] = (GLubyte) c;
            checkImage[i][j][3] = (GLubyte) 255;
            c = ((((i&0x10)==0)^((j&0x10))==0))*255;
            otherImage[i][j][0] = (GLubyte) c;
            otherImage[i][j][1] = (GLubyte) 0;
            otherImage[i][j][2] = (GLubyte) 0;
            otherImage[i][j][3] = (GLubyte) 255;
        }
    }
}
void init(void)
{    
    glClearColor (1.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_FLAT);
    glEnable(GL_DEPTH_TEST);

    makeCheckImages();
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    glGenTextures(2, texName);
    glBindTexture(GL_TEXTURE_2D, texName[0]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
        GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
        GL_NEAREST);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, checkImageWidth,
        checkImageHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE,
        checkImage);

    glBindTexture(GL_TEXTURE_2D, texName[1]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
        GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
        GL_NEAREST);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);   
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, checkImageWidth, 
        checkImageHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, 
        otherImage);
    glEnable(GL_TEXTURE_2D);

    engineGL.current.tex = texName[1];
}

But when I check the values of texName[0] and [1] they are both 0, I do not understand why, what am I doing wrong. Thanks.

Answer 1

Try calling glGetError. It should tell you in more detail what went wrong. In general, if an OpenGL function fails, the first thing you do should be to ask OpenGL why it failed. It knows, because it just tried to execute the function.

It’s much harder for us to guess at what might have gone wrong.