Helps to make 3d pen drawing from photo:
1. Arrange the objects on the plane with the reference points, such as inside a square. Projections of items must be inside of the projection of the square.
2. Superpose corners of the red square with the reference points on the image.
3. Push the cogwheel-button to convert.
The program converts 3d scene to flat projection. Now you can draw this picture and have 3d pen drawing. Use auxiliary lines on the image to draw it on a sheet of paper. Or send per email and print out!