"Physical constraints are closely related to real affordances: For example, it is not possible to move the cursor outside the screen: this is a physical constraint. Locking the mouse button when clicking is not desired would be a physical constraint. Restricting the cursor to exist only in screen locations where its position is meaningful is a physical constraint.
Logical constraints use reasoning to determine the alternatives. Thus, if we ask the user to click on five locations and only four are immediately visible, the person knows, logically, that there is one location off the screen. Logical constraints are valuable in guiding behavior. It is how the user knows to scroll down and see the rest of the page. It is how users know when they have finished a task. By making the fundamental design model visible, users can readily (logically) deduce what actions are required. Logical constraints go hand–in–hand with a good conceptual model.
Cultural constraints are conventions shared by a cultural group. The fact that the graphic on the right–hand side of a display is a 'scroll bar' and that one should move the cursor to it, hold down a mouse button, and 'drag' it downward in order to see objects located below the current visible set (thus causing the image itself to appear to move upwards) is a cultural, learned convention. The choice of action is arbitrary: there is nothing inherent in the devices or design that requires the system to act in this way. The word 'arbitrary' does not mean that any random depiction would do equally well: the current choice is an intelligent fit to human cognition, but there are alternative methods that work equally well.
A convention is a constraint in that it prohibits some activities and encourages others. Physical constraints make some actions impossible: there is no way to ignore them. Logical and cultural constraints are weaker in the sense that they can be violated or ignored, but they act as valuable aids to navigating the unknowns and complexities of everyday life. As a result, they are powerful tools for the designer. A convention is a cultural constraint, one that has evolved over time. Conventions are not arbitrary: they evolve, they require a community of practice. They are slow to be adopted, and once adopted, slow to go away. So although the word implies voluntary choice, the reality is that they are real constraints upon our behavior. Use them with respect. Violate them only with great risk."
"In this way the puppeteers would be part of the development of the prototypes for the virtual puppets as well as the characters for the play, before the actual rehearsals would begin two month later. ...
The value of the actual meetings and workshops can not be emphasised enough. This gave the participants hands on experience with the constraints in the actual equipment and a chance to meet the team that would be responsible for operating it. It is not until the artist has a very physical and intuitive impression of the material and the involved people the creative process takes off for real–before this everything is abstract ideas. ...
In the planning of the research project and the actual production the division of labour within and between each field of activity were specified as outlined in section 3.
As the process went on the borders became more blurred exploring the new field between creative production in theatre and animation and methods from computer science and systems development. One of the big challenges was the development of a common language between the artist and the programmer/technicians and to define and invent new methods that were necessary to carry out the production.
I tried to explore the numerous reasons for this in the evaluation phase of the project. This was done by conducting qualitative interviews with the participants and by reviewing the large body of video documentation from the process. The footage was edited to a 50 minute documentary about the project on which the following assumptions are based (Callesen 2001)."
(Jørgen Callesen, 2003, p.15,18,30)
Callesen (2001) Virtual Puppets in Performance, Proceedings, Marionette: Metaphysics, Mechanics, Modernity, International Symposium, University of Copenhagen, 28. March – 1. April, 2001
Callesen, J. (2003) "The Family Factory – Developing new Methods for Live 3D Animation" in Madsen, K.H. Production methods: behind the scenes of virtual inhabited 3D worlds. Springer–Verlag, London.