Text entry devices, Display Devices, Devices for virtual reality and 3D interactions

Notes

Study Notes

HCI Notes: Devices and Interactions

HCI Devices and Interaction Techniques

A review of input, output, and specialized hardware for modern interaction.

1. Text Entry Devices

Text input is the most fundamental form of human-computer communication. Efficiency and error rate are critical measures for these devices.

Standard Keyboards (QWERTY)

  • **Dominant Form:** Universal standard due to familiarity (despite non-optimal layout).
  • **Efficiency:** Measured in Words Per Minute (WPM).
  • **Alternatives:** Dvorak or Maltron layouts aim for faster WPM and reduced strain but lack universality.

Compact & Virtual Keyboards

  • **T9/Multitap:** Older method for mobile phones, relying on predictive text.
  • **Virtual (Touchscreen):** Relies on auto-correction and layout optimization (e.g., QWERTY, sometimes split for thumbs).
  • **Swiping/Gesture Typing:** Entering text by sliding a finger across keys, improving efficiency on touchscreens.

Speech Recognition (VUI)

Speech input offers a hands-free, natural mechanism for text entry, but faces challenges:

  • **Accuracy:** Highly dependent on background noise, accent, and vocabulary size.
  • **Disadvantage:** Lack of privacy and difficulty editing/correcting text quickly.
  • **Use Case:** Excellent for transcription and command execution in situations where hands or eyes are busy (e.g., driving).

2. Display Devices

The visual display is the primary output channel, converting computational data into perceivable information.

Standard Displays (LCD/OLED)

  • **Resolution:** The number of pixels ($W \times H$). Higher density (PPI) allows for finer detail.
  • **Refresh Rate:** How often the image is updated (Hz). Higher rates reduce flicker and improve motion smoothness (critical for gaming/VR).
  • **Contrast & Brightness:** Key factors in visual comfort and usability in different lighting conditions.

Shared and Public Displays

  • **Wall Displays/Projectors:** Used for collaboration, presentations, or public information. Require high brightness and low viewing angle distortion.
  • **Interactive Whiteboards:** Combine projection with touch input for collaborative, direct manipulation.

Head-Up Displays (HUDs)

Information is displayed in the user's field of vision, overlaying the real world.

  • **Usage:** Originally aviation, now cars and specialized contexts.
  • **Benefit:** Allows the user to maintain focus on the real world while receiving critical data.

3. VR and 3D Interaction Devices

These devices manage the spatial input and immersive output necessary for 3D and virtual environments.

Head-Mounted Displays (HMDs) - Output

  • **Function:** Provide stereoscopic vision for depth perception and a wide Field of View (FoV) for immersion.
  • **Key Metric:** Low latency (delay) is essential to prevent **simulator sickness** (nausea).
  • **AR vs. VR:** VR fully blocks the real world; AR overlays digital content onto the real world (e.g., smart glasses).

3D Positional Trackers - Input

  • **Hand Controllers:** Devices tracked in 3D space, often providing haptic feedback. Used for pointing, grasping, and teleportation.
  • **Data Gloves:** Wearable devices that measure finger flexion and hand posture, allowing for fine-grained interaction and gesture recognition.
  • **Body Tracking:** Full-body suits or external cameras (e.g., Kinect) used to capture the user's overall physical movement.

Spatial Interaction Techniques

  • **Pointing and Raycasting:** Using a controller to point a virtual ray at distant objects for selection.
  • **World-in-Miniature (WIM):** Manipulating a smaller, 3D replica of the virtual environment to navigate the full-scale world.
  • **Walking/Locomotion:** Techniques to move the user's viewpoint through the virtual world (e.g., physical walking, teleportation, continuous joystick movement).

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