Hi all, I sent an email named "Lightray problem" yesterday. After updating yt to the latest tip, the problem is gone. Sorry for the confusion I caused. Thanks, Pengfei -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.spacepope.org/pipermail/yt-dev-spacepope.org/attachments/20161011/8fc7b291/attachment.htm>