 twgl.setUniforms(programInfo, {
        u_tex: fbiB.texture,
        u_matrix: mat,
      });
    }
    
    twgl.drawBufferInfo(gl, cubeBufferInfo);
  }
  
  function drawTextureAToCanvas() {
    // --------
    // draw dstFB.texture to canvas
    bindFramebufferAndSetViewport(gl, null);
    
    twgl.setBuffersAndAttributes(gl, programInfo, quadBufferInfo);
    
    {
      const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
      const near = -1;
      const far = 1;
      let mat = m4.ortho(