 dstFB using srcFB.texture on cube
    bindFramebufferAndSetViewport(gl, fbiA);
    gl.clear(gl.COLOR_BUFFER_BIT);
    
    twgl.setBuffersAndAttributes(gl, programInfo, cubeBufferInfo);
    
    {
      const fov = 60 * Math.PI / 180;
      const aspect = fbiA.width / fbiA.height;
      const near = 0.1;
      const far = 100;
      let mat = m4.perspective(fov, aspect, near, far); 
      mat = m4.translate(mat, [0, 0, -2]);
      mat = m4.rotateX(mat, time);
      mat = m4.rotateY(mat, time * 0.7);

     