OpenGL texture mapping disables shading

Question

My current openGL application is just a sphere and a floor, with lighting and shading working properly.

After adding a 2d texture to the floor via the redbook tutorial: http://fly.cc.fer.hr/~unreal/theredbook/chapter09.html

.. my shading becomes disabled. If I disable GL_TEXTURE_2D, everything renders correctly, but the texture obviously does not show up. Is this a known issue with with a known workaround? Here is a bit of the code for reference:

#define    checkImageWidth 64
#define    checkImageHeight 64
GLubyte checkImage[checkImageWidth][checkImageHeight][3];

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

       for (i = 0; i < checkImageWidth; i++) {
        for (j = 0; j < checkImageHeight; 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;
        }
    }
}


void initImage() {

    makeCheckImage();
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexImage2D(GL_TEXTURE_2D, 0, 3, checkImageWidth, 
        checkImageHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, 
        &checkImage[0][0][0]);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
        GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, 
        GL_NEAREST);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
}

And then of coarse the ground draw function:

void makeGround() {

    GLfloat mat_specular[]      = { 0.5, 0.5, 0.5, 0.5 };
    GLfloat mat_diffuse[]       = { 0.3, 0.3, 0.3, 0.3 };
    GLfloat mat_shininess[]     = { 25.0 };

    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);

    glColor3f(0.2, 0.2, 0.2);

    glBegin(GL_QUADS);
        glTexCoord2f(0.0, 0.0); glVertex3f(-100.0f, -1.0f, -100.0f);
        glTexCoord2f(0.0, 1.0); glVertex3f(-100.0f, -1.0f,  100.0f);
        glTexCoord2f(1.0, 1.0); glVertex3f( 100.0f, -1.0f,  100.0f);
        glTexCoord2f(1.0, 0.0); glVertex3f( 100.0f, -1.0f, -100.0f);
    glEnd();
    glFlush();

}

if you need to see any additional portions of the code, just let me know

Bahbar Bahbar · Accepted Answer · 2011-12-01T16:53:01

glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);

Decal is a weird environment mode. For GL_RGB textures (like yours) it replaces the color. For RGBA textures, it blends it with the Alpha coming from the texture.

If you just want to modulate your texture with the lighting, use GL_MODULATE

OpenGL texture mapping disables shading

1 Answers