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OpenGL - How can I make this program work for textures larger than 1x1?

I am writing a proof of concept program to get more familiar with textures, but it's acting strangely in that it works for 1x1 textures but fails for all others. I scanned the program many times and looked over the arguments of each function, but can't understand why it works correctly for 1x1 textures(or first pixel in larger textures), but shows a white square otherwise.

Here's a picture of the same program running with glTexImage2D's width and height arguments (1, 1) and (2,2) respectively.

texture width, height -> 1,1 texture width, height -> 2,2

This is the code that shows a white square(Whereas expected to draw a 2x2 red,green,blue, yellow row major texture).

note: in(Comment, Arg) macro is equivelent to Arg, it's only used in this particular program because it's tricky to remember arguments of glTexImage2D off the top of your head.

#include <GL/glut.h>

// | reminder decorator macro.
#define in(Comment, Arg) Arg

GLubyte bm[16] = {
    0xff, 0x00, 0x00, 0xff,
    0x00, 0xff, 0x00, 0xff,
    0x00, 0x00, 0xff, 0xff,
    0xff, 0xff, 0x00, 0xff
};

GLuint tex;

void display()
{
    glClear(GL_COLOR_BUFFER_BIT);           

    glBindTexture(GL_TEXTURE_2D, tex);

    glLoadIdentity();

    // | make the square smaller to contrast our target from the background.
    glScalef(.5f, .5f, 1.f);

    glBegin(GL_TRIANGLE_FAN);
        glTexCoord2f(0.f, 0.f);
        glVertex2f(-1.f, 1.f);
        glTexCoord2f(0.f, 1.f);
        glVertex2f(1.f, 1.f);
        glTexCoord2f(1.f, 1.f);
        glVertex2f(1.f, -1.f);
        glTexCoord2f(1.f, 0.f);
        glVertex2f(-1.f, -1.f);
    glEnd();

    glFlush();
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE);
    glutCreateWindow("");

    glEnable(GL_TEXTURE_2D);        
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexImage2D (
        in(target, GL_TEXTURE_2D), 
        in(level, 0), 
        in(internalFormat, GL_RGBA), 
        in(width, 2), 
        in(height, 2), 
        in(border, 0), 
        in(format, GL_RGBA), 
        in(type, GL_UNSIGNED_BYTE), 
        in(data, bm)
    );
    glTexParameteri(tex, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(tex, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    glutDisplayFunc(display);
    glutMainLoop();

    return 0;
}

if I change in(width, 2) to in(width, 1) and in(height, 2) to in(height, 1), it shows a red square, and altering the first three values of bm array, it maps this color to the cube as expected.

#include <GL/glut.h>

// | reminder decorator macro.
#define in(Comment, Arg) Arg

GLubyte bm[16] = {
    0xff, 0x00, 0x00, 0xff,
    0x00, 0xff, 0x00, 0xff,
    0x00, 0x00, 0xff, 0xff,
    0xff, 0xff, 0x00, 0xff
};

GLuint tex;

void display()
{
    glClear(GL_COLOR_BUFFER_BIT);           

    glBindTexture(GL_TEXTURE_2D, tex);

    glLoadIdentity();

    // | make the square smaller to contrast our target from the background.
    glScalef(.5f, .5f, 1.f);

    glBegin(GL_TRIANGLE_FAN);
        glTexCoord2f(0.f, 0.f);
        glVertex2f(-1.f, 1.f);
        glTexCoord2f(0.f, 1.f);
        glVertex2f(1.f, 1.f);
        glTexCoord2f(1.f, 1.f);
        glVertex2f(1.f, -1.f);
        glTexCoord2f(1.f, 0.f);
        glVertex2f(-1.f, -1.f);
    glEnd();

    glFlush();
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE);
    glutCreateWindow("");

    glEnable(GL_TEXTURE_2D);        
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexImage2D (
        in(target, GL_TEXTURE_2D), 
        in(level, 0), 
        in(internalFormat, GL_RGBA), 
        in(width, 1), 
        in(height, 1), 
        in(border, 0), 
        in(format, GL_RGBA), 
        in(type, GL_UNSIGNED_BYTE), 
        in(data, bm)
    );
    glTexParameteri(tex, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(tex, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    glutDisplayFunc(display);
    glutMainLoop();

    return 0;
}

Can somebody explain what is happening and how I can solve this issue?

Solution: passed tex to glTexParameteri instead of GL_TEXTURE_2D(side note: and a typo 1.1 to 1.f in glVertex2f)

#include <GL/glut.h>

// | reminder decorator macro.
#define in(Comment, Arg) Arg

GLubyte bm[16] = {
    0xff, 0x00, 0x00, 0xff,
    0x00, 0xff, 0x00, 0xff,
    0x00, 0x00, 0xff, 0xff,
    0xff, 0xff, 0x00, 0xff
};

GLuint tex;

void display()
{
    glClear(GL_COLOR_BUFFER_BIT);           

    glBindTexture(GL_TEXTURE_2D, tex);

    glLoadIdentity();

    // | make the square smaller to contrast our target from the background.
    glScalef(.5f, .5f, 1.f);

    glBegin(GL_TRIANGLE_FAN);
        glTexCoord2f(0.f, 0.f);
        glVertex2f(-1.f, 1.f);
        glTexCoord2f(1.f, 0.f);
        glVertex2f(1.f, 1.f);
        glTexCoord2f(1.f, 1.f);
        glVertex2f(1.f, -1.f);
        glTexCoord2f(0.f, 1.f);
        glVertex2f(-1.f, -1.f);
    glEnd();

    glFlush();
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE);
    glutCreateWindow("");

    glEnable(GL_TEXTURE_2D);        
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexImage2D (
        in(target, GL_TEXTURE_2D), 
        in(level, 0), 
        in(internalFormat, GL_RGBA), 
        in(width, 2), 
        in(height, 2), 
        in(border, 0), 
        in(format, GL_RGBA), 
        in(type, GL_UNSIGNED_BYTE), 
        in(data, bm)
    );
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    glutDisplayFunc(display);
    glutMainLoop();

    return 0;
}

solved

Solution

  • When you specify a 2x2 texture, your texture is not mipmap-complete, but you use a mip-mapping minification filter. The result you get is the correct result, as per the specification.

    Your mistake lies in your attempt to set the non-mipmapping GL_NEAREST filter:

    glTexParameteri(tex, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

    glTexParameter expects the texture binding point, which would be GL_TEXTURE_2D, not the texture name. As a result, this call will generate GL_INVALID_ENUM error and has no other effect.