var captureFrame = false;
//for doing something just before render
window.addEventListener('before_frame_render', function(){        
 if(window.captureFrame == true){
  if (captureFrame) {
        captureFrame = false;                      //captureFrame is false until the next click
        var awecanvas = document.getElementById('awe_canvas-0');
        awecanvas.getContext("webgl", {preserveDrawingBuffer: true}); //preserves the  buffer
        var dataURL = awecanvas.toDataURL();
         $.ajax({
          type: "POST",
          url: "saveImage.php",
          data: {
            imgBase64: dataURL,
            }
          }).done(function(str) {  // response 
          });
      }
    }
  });

//On click of capture button
 document.getElementById("capture").addEventListener("click", function(){ 
      captureFrame = true;
 });