An Interactive System for Knot Design

In everyday life, knot has many practical uses that are usually overlooked such as shoelacing. In  sports and  activities like sailing and rock climbing, a knot can mean life or death.  In addition to its widely recognized practicality and aesthetic, knot now plays an important role in modern surgery too. A logical extension to the digital world is to model these objects in virtual space. To  the  computer graphics  community,  the more easily a complex model is created, the richer its visual content becomes. link  fence, or a part of armor suit  are commonly seen in games and movies. With more computational power, adding such models can provide more realistic credibility or even more correct physical interaction to graphical scene. By its nature of self-occlusion and complicated topology,  3-D model is a suitable medium to  represent knot. Currently most knot-related  books  and  websites  provide a series of still diagrams or photos to describe how to tie a knot. Although the mean is easy to interpret, creating such diagrams or photos requires much preparation and time. 3-D model is rarely used as learning material. In traditional  3-D modeling programs, knots can be modeled  by first creating a spline in a 2-D view and then editing the depths of the necessary parts. These steps can be confusing and counterintuitive because the depth or the relationship between parts is usually determined during the creative process, not afterwards. In addition, the lack of physical properties such as collision and friction does not allow the knot to be tightened or modified as it could in reality. The knots that are created by traditional 3D modeling software packages are usually in their loosened forms as modeling a tight knot from the start is very hard. Those knots are not of many uses because knot is  useful  and  found  in  everyday  life  only in its tightened  form which can be totally different from its loosened form in terms of both appearance and physical properties. There are two main reasons why faithful models of interwoven objects have not been widely used.  One is due to technical limitation which will be overcome by faster and more advanced  technology. The other is that current modeling tools are not designed for such objects. Existing modeling paradigm doesn’t allow easy creation and artists cannot freely add creative process into their work routine. Also designing interface for knot tying is challenging as it is claimed to be diffcult for normal users because manipulating interweaving model requires a lot of creativity and practice to give exact and economical commands especially for deformable model. The main goal of our research is to make design of 3-D knots easier by introducing specialized user interface tailored to physical knot tying. With sketching gestures and automatic depth inference,  we  can  eliminate  the  necessity of manually setting  each control point in a traditional approach.  Even in the most sophisticated 3-D modeling systems, several geometric view changes  are required to rotate working model into proper orientation in order to set correct depth.  In our system, user can create a knot model as if drawing a knot diagram on paper from only one perspective. This system also adds interactive physical simulation into the design process, which supports the user’s experiments and helps in the overall visual quality of the design result.