| The nature of highway is a 3D spatial linear structure. Current methods design the highway horizontal and vertical alignments separately in 2D platform through 1D keyboard and 2D mouse, and then combine the alignments into a 3D highway space curve. These methods totally violate highway’s 3D nature: firstly, the insufficient interaction bandwidth provided by the 2D interaction tools and design platform results in the directly interaction design and the 3D uniformly display of highway space curve entity is very difficult. Secondly, the curve description model of current design methods is 2D, which brings out a typically fragmental piecing up design type and is difficult to accurately describe a highway space curve. Furthermore, the 2D curve model results in the conjunction and coupling of the 2D horizontal and vertical alignments design, and the complex design constraint indexes and design steps.In order to make the highway design is fully compatible with its nature, this paper analyses the research status of current highway 3D visualization design systems, and clears that the 3D design platform, 3D human-computer interaction and 3D curve description model are the essential features for a highway true 3D design system. Then the paper proposes the new highway true 3D design method based on motion sensing, and puts the research framework of which and the system design of the motion sensing-based highway true 3D design system. On this basis, the paper studies on the gesture-based natural user interface for highway space curve design and the 3D unified description model of highway space curve in detail, which are the two key issues for the development of the motion sensing-based highway true 3D design system. The study in this paper has gained the following achievements:(1) This paper puts forward the motion sensing-based true 3D highway design method that directly uses gesture as only human computer interaction tool and designs a highway space curve in virtual environment with realistic landscape through perceiving human body’s motion, and then studies and analyzes the function goals, architecture, function models and work flow of the motion sensing-based true 3D highway design system. Finally, the comparisons between the motion sensing-based true 3D highway design method and current 2D design method are carried out, and the results of which show that the motion sensing-based true 3D highway design method can provide a 3D design platform, 3D human computer interaction and 3D highway space curve description model through closely integrating gesture-based natural user interface, 3D unified highway space curve description model and 3D geographic information system. Consequently, the motion sensing-based true 3D highway design method is a new ideal to realize true 3D highway design.(2) A gesture-based 3D natural user interface for highway space curve design is developed in this paper, including the studies on functional goals, components, interaction gesture, control parameter system, and gesture recognition method. According to different interaction tasks, this article uses Kinect and arm motion for 3D virtual environment navigation and uses Leap Motion and finger gesture for 3D highway curve entity manipulation in a creative way, and thus achieves the balance between comfortable and efficient navigation and accurate curve design. Moreover, in accordance with the nature language gesture recognition and the characteristics of interaction gesture for highway space curve design, this paper improves the finite-state machine matching algorithm based on pose snapshots of multiple joints, and thus realizes the stable and efficient recognition of interaction gesture. The studies on gesture-based natural user interface builds up the bridge to connect the physical space and virtual design space, and successful solves the prerequisite of the true 3D highway design.(3) The model and algorithm of the spatial quartic Bezier piecewise interpolation curve to achieve the unified mathematical description of 3D highway space curve. After designer inputs a set of ordered space control point, the true 3D highway design system estimates the tangent direction and curvature vector in each control point through constructing a cubic spline to use as the initial construction conditions of a quartic Bezier curve with one degree of freedom that used for constructing a complete 3D space interpolation curve. The highway space curve obtained by the construction method proposed in this paper is local shape-modifying and G~2 continuous. Furthermore, the one extra degree of freedom can be used to control and modify the curve shape to ensure the curvature and torsion of which meet the requirements of 3D highway space curve design index system. These advantages can help achieve the automation and intelligent of highway design work.To verify the feasibility and effectiveness of motion sensing-based true 3D highway design method, this paper uses the Google Earth as the 3D design platform to develop a prototype system. The user tests show that the combination of gesture-based 3D natural user interface and the unified mathematical description of 3D highway space curve can achieve the direct interaction design of the 3D highway curve entity in virtual environment with gesture, and the 3D stereo visualization of the highway space curve, and thus obtain total integration of both alignment design process and 3D visualization process to realize the synchronous visualization of design process.The research findings of this paper solves the two key issues true 3D highway design facing, including the 3D human computer interaction and 3D unified mathematical description of highway space curve. Therefore, this paper provides a new thought and direction for promoting the development of highway design work towards true 3D method and improving the quality of highway design, but also lays a solid foundation for further studies on cross alignment design, highway panoramic engineering model, 3D safety evaluation and so on. |
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