new GUI
new Viewer
Add viewer
Merge

Merge branch 'master' of github.com:ylwu/HackMIT
Merge branch 'master' of github.com:ylwu/HackMIT
Merge branch 'master' of github.com:ylwu/HackMIT
Merge branch 'master' of github.com:ylwu/HackMIT
zoomin
merge resolved