A Scaffold-Based Tool for Product Design Variations in Virtual Reality

Research Background and Problem

• Identified Issues or Challenges: The authors observed that in product design, while analytic drawing (using guide lines or "scaffolds" to assist in creating shape curves) and freehand sketching are common design methods, modifying existing sketch variants is highly challenging. This is due to the complex relationships between scaffold lines, shape curves, and detail curves. Iterative design often requires designers to redraw the entire process from scratch, slowing down the design workflow.
• Significance of the Problem: Product design is a process that emphasizes iterative exploration, but existing tools do not adequately support scaffold-based design modifications, especially when generating design variants. This limits designers' creativity and exploratory capabilities.
• Research Motivation and Related Work: While previous studies have attempted to elevate 2D drawing to 3D (e.g., Gryaditskaya et al., 2020; Hähnlein et al., 2022) or support virtual reality painting (e.g., Yu et al., 2021), these methods focus on creation rather than editing and fail to address how to explore scaffold-supported design variants in 3D models.

Solution

• Proposed Method or Solution: The authors developed a virtual reality tool that allows designers to directly manipulate 3D scaffold lines and add freely drawn detail strokes. The system automatically defines and adjusts constraints based on scaffold edits and updates the model's shape curves and detail curves to match the new scaffold configuration.
• Innovations:
  1. Proposed a method for generating design variants through scaffold editing, treating scaffolds as natural interaction handles.
  2. Implemented dynamic addition, release, and optimization algorithms for scaffold constraints to maintain aesthetic shapes.
  3. Integrated support for detail strokes in the tool, enabling users to freely draw and automatically adjust detail curves to match scaffold changes.
• Implementation Steps and Key Techniques:
  1. User Interface: Users can directly select, drag, rotate, and scale scaffold lines in virtual reality, with these operations triggering real-time updates and optimizations of model constraints.
  2. Scaffold Optimization: The system detects broken and newly introduced constraints (e.g., parallelism, perpendicularity, equal length) in the scaffold and optimizes them using an iterative reweighted least squares method.
  3. Shape Curve Adjustment: Key points and tangent directions of shape curves are automatically updated based on scaffold adjustments, with curve smoothness optimized through minimal curvature changes.
  4. Detail Curve Deformation: Detail curves are represented using generalized barycentric coordinates, with control points stored as linear combinations of scaffold points, allowing curves to naturally deform as scaffolds change.

Research Outcomes

• Specific Achievements:
  1. Developed a scaffold-based virtual reality tool that enables users to generate various design variants by directly manipulating 3D scaffolds.
  2. Provided functionality for users to draw and adjust detail lines during the design process, maintaining flexibility and naturalness in the design.
• Advantages Over Existing Solutions:
  1. Offers direct and natural interaction support for scaffolds, whereas existing digital deformation tools (e.g., Blender or Illustrator) typically lack support for or overlook geometric constraints of scaffolds.
  2. The system's scaffold optimization and automatic adjustment algorithms expand operational possibilities while reducing inevitable human errors in manual operations.
  3. The tool combines the strengths of analytic drawing and digital deformation techniques, creating a "hybrid" design paradigm.
• Experimental and Evaluation Results:
  1. The authors validated the tool's practicality, time-saving benefits, and ease of use through empirical studies with professional product designers, including video demonstrations, remote testing, and hands-on user operations.
  2. Expert feedback indicated that the tool facilitates rapid generation of design variants, simplifies iterative workflows, and maintains the aesthetic and structural quality of sketch designs.
  3. The tool's performance in detail adjustment and shape curve deformation was recognized by users, particularly in how detail lines naturally followed scaffold changes.
• Limitations and Future Directions:
  1. Topological Constraints: The current system does not support dynamic addition or removal of lines in the scaffold, limiting editing flexibility. Future work could explore automatic scaffold generation.
  2. Input Requirements: The system requires pre-existing optimized 3D scaffold sketches, while most designers primarily work with 2D sketches. Research is needed to effectively handle noisy or unstructured inputs.
  3. Adaptation to 2D Drawing: Although the authors discussed the potential application of the tool to 2D design, this has not been implemented, representing a potential area for future expansion.
  4. User Interface Improvements: Some users suggested adding features such as model layering, side-by-side variant display, and more precise control options, which could enhance the user experience.

Through the development and validation of the scaffold-based design variant tool, this study paves the way for further research in industrial design and virtual reality interaction tools, providing designers with a flexible, natural, and efficient method of operation.