Unable to make opengl texture working properly

Question

I am trying to draw a simple cube with vbos. But when I run my program I dont get the expected result. Whereas being textured, my cube is fully opaque with one color of my texture...

You can see below my code :

loading of the texture with SFML:

void Grass::load() {
    sf::Image texture;

    if (!texture.loadFromFile(path_m))
        std::cerr << "Error while loading texture : " << path_m << std::endl;
    else {
        glGenTextures(1, &id_m);

        glBindTexture(GL_TEXTURE_2D, id_m);
        {
            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texture.getSize().x,
                    texture.getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE,
                    texture.getPixelsPtr());

            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        }
        glBindTexture(GL_TEXTURE_2D, 0);
    }
}

Generation of the vertices of the cube:

void Chunck::generate() {

    {
        std::vector vec = { -1.0, -1.0, -1.0, 1.0, -1.0, -1.0, 1.0, 1.0, -1.0, // Face 1
                -1.0, -1.0, -1.0, -1.0, 1.0, -1.0, 1.0, 1.0, -1.0,     // Face 1

                1.0, -1.0, 1.0, 1.0, -1.0, -1.0, 1.0, 1.0, -1.0,       // Face 2
                1.0, -1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, -1.0,         // Face 2

                -1.0, -1.0, 1.0, 1.0, -1.0, 1.0, 1.0, -1.0, -1.0,      // Face 3
                -1.0, -1.0, 1.0, -1.0, -1.0, -1.0, 1.0, -1.0, -1.0,    // Face 3

                -1.0, -1.0, 1.0, 1.0, -1.0, 1.0, 1.0, 1.0, 1.0,        // Face 4
                -1.0, -1.0, 1.0, -1.0, 1.0, 1.0, 1.0, 1.0, 1.0,        // Face 4

                -1.0, -1.0, -1.0, -1.0, -1.0, 1.0, -1.0, 1.0, 1.0,     // Face 5
                -1.0, -1.0, -1.0, -1.0, 1.0, -1.0, -1.0, 1.0, 1.0,     // Face 5

                -1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, -1.0,         // Face 6
                -1.0, 1.0, 1.0, -1.0, 1.0, -1.0, 1.0, 1.0, -1.0 };     // Face 6
        vertices_m.insert(vertices_m.begin(), vec.begin(), vec.end());
    }

    {
        std::vector vec = {0, 0,   1, 0,   1, 1,     // Face 1
                0, 0,   0, 1,   1, 1,     // Face 1

                0, 0,   1, 0,   1, 1,     // Face 2
                0, 0,   0, 1,   1, 1,     // Face 2

                0, 0,   1, 0,   1, 1,     // Face 3
                0, 0,   0, 1,   1, 1,     // Face 3

                0, 0,   1, 0,   1, 1,     // Face 4
                0, 0,   0, 1,   1, 1,     // Face 4

                0, 0,   1, 0,   1, 1,     // Face 5
                0, 0,   0, 1,   1, 1,     // Face 5

                0, 0,   1, 0,   1, 1,     // Face 6
                0, 0,   0, 1,   1, 1};    // Face 6
        texture_m.insert(texture_m.begin(), vec.begin(), vec.end());
    }
}

Cube Drawing:

void Chunck::draw() const {

    glBindBuffer(GL_ARRAY_BUFFER, vboID_m);


    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(vertices_m.size() * sizeof(double)));
    glEnableVertexAttribArray(2);

    glBindTexture(GL_TEXTURE_2D, grassTexture_m.getID());
    glDrawArrays(GL_TRIANGLES, 0, vertices_m.size());
    glBindTexture(GL_TEXTURE_2D, 0);

    glDisableVertexAttribArray(2);
    glDisableVertexAttribArray(0);


    glBindBuffer(GL_ARRAY_BUFFER, 0);
}

Load of the cube into VBO:

void Chunck::load() {
    grassTexture_m.load();

    if (glIsBuffer(vboID_m) == GL_TRUE)
        glDeleteBuffers(1, &vboID_m);

    glGenBuffers(1, &vboID_m);
    glBindBuffer(GL_ARRAY_BUFFER, vboID_m);
    {
        glBufferData(GL_ARRAY_BUFFER, (vertices_m.size() + texture_m.size()) * sizeof(float), 0,
        GL_STATIC_DRAW);
        glBufferSubData(GL_ARRAY_BUFFER, 0, vertices_m.size() * sizeof(float), vertices_m.data());
        glBufferSubData(GL_ARRAY_BUFFER, vertices_m.size() * sizeof(float),
                texture_m.size() * sizeof(float), texture_m.data());
    }
    glBindBuffer(GL_ARRAY_BUFFER, 0);

}

Answer 1

The data type of the vertices is float , so the buffer offset is BUFFER_OFFSET(vertices_m.size() * sizeof(float)) , instead of sizeof(double) .

glVertexAttribPointer(
    2, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(vertices_m.size() * sizeof(float)));

Are you sure that the attribute index of the texture coordinates is 2 ? Note, the vertex attribute index can be set by Layout Qualifiers ( layout(location = 2) in vec2 texCoord; ) or it can be get by glGetAttribLocation from the shader program object.

The 3rd parameter of glDrawArrays is the number of the vertices, but not the number of elements in the array:

glDrawArrays(GL_TRIANGLES, 0, vertices_m.size() / 3);

Further I recommend to enable the Depth test , before drawing the geometry. Since the default depth function is GL_LESS , this causes that the geometry which is closer to the view position covers the geometry behind it.

glEnable( GL_DEPTH_TEST );