How to add sunglasses to face in video?

To add sunglasses to a face in a video, you can use video editing software with tracking and overlay capabilities. Import the video, apply tracking to the face, and overlay the sunglasses image. Adjust position, size, and transparency for a natural look. Ensure the software supports these features for desired results.

The workflow you would use depends on the footage. There are workflows that use just the Face Tracker, or you can jump up to Fact Tracking Camera Tracking/Element 3D or to Object tracking using a free plugin from GeoTracker.

Take a look at this tutorial:

and take into account perspective of the glasses?

Not really. That would require inverse 3D tracking (object tracking) and actual 3D geometry. That's a task for mocha Pro or Syntheyes. You can of course still scale whatever masks or face attachments you have tracked after the fact, but it will require lots of subtle tweaks to look realistic.

Mylenium