In the spirit of architectural tracing paper, freehand sketching is easily done on model surfaces. The sketch tool makes it easy to communicate ideas and suggestions when in a meeting with other users.
The starting point of a sketch determines it's drawing plane. Sketches can be moved around, stretched, glued onto surfaces or deleted just like normal shapes.
Sketches close to each other are automatically grouped and sketches on shapes or imported assets are automatically glued to their parent. You can select the color of the sketch line using the favorites menu or the materials drawer to the right of the main menu.
Sketching is very helpful for people joining a collaborative meeting in a mobile device like tablet or smartphone as its a more user friendly input for touchscreen devices.