Example demonstrating the request in mongoose GH-246 is now supported

GH-246.js

var mongoose = require('mongoose')
, Schema = mongoose.Schema ;

var PageSchema = new Schema({
  author: {
      first_name: String
    , last_name: String
  }
});

PageSchema.virtual("author.full_name").get(function() {
  return this.author.first_name + " " + this.author.last_name;
});

var Page = mongoose.model('Page', PageSchema);

// Later
myPage = new Page({author: {first_name: "John", last_name: "Doe"}});
console.log(myPage.author.full_name); // == "John Doe"
console.log(myPage.get("author.full_name")); // == "John Doe"