gistfile1.c

    // compile the display list, store the grid in it
    glNewList(grid, GL_COMPILE);

        GLint skybox_ptr;
        skybox_ptr = glGetUniformLocation(shader, "isSkybox");
        glUniform1i(skybox_ptr, 0);

        // The actual grid
        int x, y, z;
        for (x=-MAP_HALFWIDTH; x<MAP_HALFWIDTH-1; x++)
        {
            glBegin(GL_TRIANGLE_STRIP);
                for (z=-MAP_HALFLENGTH; z<(MAP_HALFLENGTH-1); z++)
                {
                    glVertex3f(x, 0.0, -(z));
                    glVertex3f(x+1, 0.0, -(z));
                }
            glEnd();
        }

        glUniform1i(skybox_ptr, 1);

        // The skybox

        // The first two walls
        for (x=-MAP_HALFWIDTH; x<=MAP_HALFWIDTH; x+=MAP_HALFWIDTH)
        {
            glBegin(GL_TRIANGLE_STRIP);
                glVertex3f(x, -MAP_HALFHEIGHT, -MAP_HALFLENGTH);
                glVertex3f(x, MAP_HALFHEIGHT, -MAP_HALFLENGTH);
                glVertex3f(x, -MAP_HALFHEIGHT, MAP_HALFLENGTH);
                glVertex3f(x, MAP_HALFHEIGHT, MAP_HALFLENGTH);
            glEnd();
        }

        // The other two walls
        for (z=-MAP_HALFLENGTH; z<=MAP_HALFLENGTH; z+=MAP_HALFLENGTH)
        {
            glBegin(GL_TRIANGLE_STRIP);
                glVertex3f(-MAP_HALFWIDTH, -MAP_HALFHEIGHT, z);
                glVertex3f(-MAP_HALFWIDTH, MAP_HALFHEIGHT, z);
                glVertex3f(MAP_HALFWIDTH, -MAP_HALFHEIGHT, z);
                glVertex3f(MAP_HALFWIDTH, MAP_HALFHEIGHT, z);
            glEnd();
        }

        // Ceiling
        glBegin(GL_TRIANGLE_STRIP);
            glVertex3f(-MAP_HALFWIDTH, MAP_HALFHEIGHT, -MAP_HALFLENGTH);
            glVertex3f(MAP_HALFWIDTH, MAP_HALFHEIGHT, -MAP_HALFLENGTH);
            glVertex3f(-MAP_HALFWIDTH, MAP_HALFHEIGHT, MAP_HALFLENGTH);
            glVertex3f(MAP_HALFWIDTH, MAP_HALFHEIGHT, MAP_HALFLENGTH);
        glEnd();

    glEndList();