Over the last week or so, I’ve talked about cognitive load, and how it affects CAD usability. It’s time to talk more about how user interface plays into this.

A few years ago, researchers from Yonsei University, Georgia Institute of Technology, and National Cheng Kung University (Ghang Lee, Charles M. Eastman, Tarang Taunk, and Chun-Heng Ho) published a research study titled Usability principles and best practices for the user interface design of complex 3D architectural design and engineering tools, in the International Journal of Human-Computer Studies.

The reason they undertook the research study was that there was plenty of research on user interface design for generic desktop and web applications, but none for complex 3D parametric architectural design and engineering software.

Here is a summary of the user interface principles recommended by the authors:

Principles for general system design

  • Consistency: Uniformity of system semantics across similar situations.
  • Visibility: Making relevant information conspicuous and easily detectable to the user.
  • Feedback: Response of the system to the user’s actions in order to provide information regarding the internal state of the system.
  • Recoverability: Providing the user with options to recognize and recover from errors.

Principles specific to 3D parametric design

  • Maximization of Workspace: Providing maximum screen space for carrying out the primary functions of the CAD system.
  • Graphical Richness: Replacing textual information with graphical information like imagery or animation to enhance user comprehension where appropriate.
  • Direct Manipulation: Providing interaction that is perceived by the user as directly operating on an object or entity within the system.

Principles for user support

  • Familiarity: Leveraging user’s knowledge and experience in other real-world or computer-based domains when interacting with a new system.
  • Customizability: Support to explicitly modify the interface or operability of the system based on the user’s preference.
  • Assistance: Providing support to the user both explicitly, by tutoring, and implicitly, by prompting the user in the right direction.
  • Minimalist design: Keeping the design simple and minimizing redundancy of information when it threatens to be the cause of confusion to the user.
  • Context recognition: Automatic adjustment of the interface or operability of the system based on user mode and, system context.

Here’s a significant comment from the study’s summary:

Complex 3D design and engineering systems are usually composed of several hundred menu items. If options for each menu item are considered, the combination of possible operations grows exponentially. Since this number exceeds the cognitive load that a person can handle, an efficient and user-friendly UI is critical to the users of these systems.

Cognitive Load. Just like I’ve been talking about for the last week or so of posts here.

If you’re interested in CAD user interface issues, you should read the study from the link above. It’s well worth the time.