Touch-based Interactive NURBS Modeler

Abstract

The creation of complex NURBS surfaces in design environments is a tedious process because very few tools exist, that allow a designer to design intuitively in real-time. Standard input devices such as the mouse and the keyboard do not provide the designer with direct and easy capabilities for surface manipulation.

The methods used for free-form curve and surface modification in current CAD systems are still limited and non-intuitive. Generally designers, especially concept designers, prefer tools such as clay models, which allow artistic and aesthetic design. The human hand is perhaps the most useful and diverse tool we use to interact with the environment around us.

The CAD Modeling Glove (ModelGlove), originally developed by Mayrose (Mayrose et al. 2000) in the V.R. Lab. At UB was adapted as an innovative new interface between the real world and the 3D NURBS model, by capturing the action of the user's hand including pressure and position of the fingers. This input device is equipped with force and position sensors for quantifying touch and intent of the designer. The goal behind the development of the ModelGlove is to provide designers with a tool, which will allow them to touch, push, and manipulate virtual objects, just as they would model real clay models or sculptures.

The software for the proposed modeling system has been developed in C++ using Visual Studio 6.0 as the compiler. The Graphical User Interface for the software was developed in C++ on the OpenGL platform using GLUI libraries. The on-screen GUI controls sculpting parameters and provides visual feedback about the position and the force/position applied by the user. In the proposed modeling system, a NURBS surface representation is created that helps the designer to modify an existing free-form surface (parent surface), in a natural and intuitive manner. A preset NURBS surface block is initialized at the start of the program using OpenGL NURBS evaluators. The surface is structured in such a manner that the control points of the block are updated dynamically in response to the force applied by the designer in real life.

The new surface is generated by adding a displacement function to the parent surface. The overall deformation of the parent surface can be viewed as the weighted average of the control vectors. Real time update of the NURBS block using the ModelGlove provides a highly interactive feeling to the designer. The designer defines a point on the NURBS surface. Depending upon his or her choice of tool, the force applied and the position, the surface is locally deformed within the specified influence radius of the tool tip.

Publications
[1] Kamerkar, A., and Kesavadas, T., "Touch Based Interactive NURBS Modeler using a Force/Position Input Glove", ASME Design and Technology Conferences, Salt Lake City, Utah, Sept. 2004.