 ['NEAREST_MIPMAP_NEAREST',true],
    ];

    const fb = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fb);

    debug(`
        mips: ${MIPS}: [0,${MIPS-1}] (inclusive)
        size: ${SIZE}`);
    const texs = [
        immutTex,
        mutTex,
    ];
    for (const tex of texs) {
        debug(`\

            immutable: ${tex.immutable}`);
        gl.bindTexture(gl.TEXTURE_2D, tex);

        for (const level_prime_base of range(MIPS+1)) { // `level_base` in GLES
            // ES 3.0.6 