code: function renderPick() {
      if(checkContextLoss()) {
        return
      }
  
      gl.colorMask(true, true, true, true)
      gl.depthMask(true)
      gl.disable(gl.BLEND)
      gl.enable(gl.DEPTH_TEST)
  
      var numObjs = objects.length
      var numPick = pickBuffers.length
      for(var j=0; j<numPick; ++j) {
        var buf = pickBuffers[j]
        buf.shape = pickShape
        buf.begin()
        for(var i=0; i<numObjs; ++i) {
          if(pickBufferIds[i] !== j) {
            continue
          }
          var obj = objects[i]
          if(obj.drawPick) {
            obj.pixelRatio = 1
            obj.drawPick(cameraParams)
          }
        }
        buf.end()
      }
    }
docs: Render the scene for mouse picking