Adaptive Control Point Manipulation Technique for Free-Form Deformation Based on Gesture Interaction

Abstract: Currently, the majority of Computer-Aided Design (CAD) software adopts a feature-based parametric modeling approach, which effectively captures and represents the detailed attributes of design objects. Despite its precision and utility, this method demands extensive parameter adjustments within the constructed solid models to accommodate design modifications. Such complexity imposes significant constraints on the fluidity and flexibility required during the conceptual design phase, thereby impeding the expression of innovative design ideas. Furthermore, traditional CAD software predominantly relies on the "mouse and keyboard" interaction paradigm. This approach maps three-dimensional manipulation commands onto one-dimensional or two-dimensional input signals, which reduces the naturalness and intuitiveness of the modeling process. Consequently, there is a pressing need to develop advanced three-dimensional modeling methodologies that support free-form deformation (FFD) and integrate novel interaction paradigms to enhance user experience and foster design creativity. The concept of free-form deformation, first introduced by Sederberg and Parry (1986), involves embedding a geometric object into a control lattice defined by a set of control points. The deformation of the lattice, driven by manipulating these control points, is propagated to the embedded object, resulting in its transformation. Over time, free-form deformation technology has evolved significantly. A method for deforming geometric models was proposed to enhance usability by replacing grid-based operations with direct point manipulation. This approach was later refined with Dirichlet free-form deformation, which automates the generation of influence regions and calculates spatial density using constraint points. Subsequently, advancements introduced adaptive control point generation, multi-resolution editing, and hierarchical deformation, significantly improving the flexibility and precision of free-form deformation techniques. Parallel to advancements in FFD, gesture-based interaction has emerged as a novel interaction technology. Gesture interaction provides a more natural and intuitive mode of operation compared to traditional WIMP user interfaces by capturing hand movements and translating them into control commands. Prior research has demonstrated that gesture-based systems are not only easier for new users to adopt but also enable more immersive and efficient manipulation of virtual objects. However, challenges remain in bridging the gap between gesture-based input and precise control in modeling environments, particularly in the context of free-form deformation. This paper proposes a gesture-based adaptive control point manipulation technique for free-form deformation, which integrates gesture interaction into the free-form deformation process. In order to address the interaction amplitude mapping issue inherent in gesture interaction, a control point adaptive manipulation method based on mapping functions is designed, aiming at improving user interaction experience and enhancing model editing efficiency during the conceptual design phase. First, the study compares and analyzes the basis functions and deformation tools of free-form deformation to optimize the initial control point layout. Three mapping functions are developed to address the mapping discrepancies between hand gesture movement speed and control point movement speed during gesture interaction. To evaluate the interaction efficiency and operation smoothness of these three mapping modes, a comparative experiment is conducted involving 15 participants, which identifies the optimal mapping mode for interaction performance. Each of the participants needs to perform 3 rounds of control point movement operations in the experimental scenarios with 5 different movement distances preset by the system, under three different mapping modes, for a total of 45 operations. Metrics recorded include task completion time, operation accuracy and user preference. An adaptive control method for control points based on the optimal mapping function is designed, defining adaptive parameters within the mapping pattern and providing an adaptive parameter adjustment method for new users. Finally, an evaluation experiment is conducted with 10 participants to assess the effectiveness of the proposed adaptive control methods. Participants are required to perform specified model deformation tasks using both the "mouse and keyboard" interaction paradigm and the gesture-based interaction paradigm. Key metrics, including interaction accuracy and user preferences, are recorded for analysis. The results indicate that the gesture-based interaction paradigm not only achieves satisfactory interaction accuracy but also offers notable advantages in terms of enhanced immersion and reduced fatigue compared to the traditional "mouse and keyboard" interaction paradigm.

Keywords: Free-form deformation, Gesture interaction, User adaptation, Human-computer interaction, CAD modeling

DOI: 10.54941/ahfe1006261

Cite this paper:

​