SubD-NURBS Workflows

SubD-NURBS is a unique and revolutionary software library that can integrate with 3D modeling systems to provide advanced integration tools that are unavailable in other 3D modeling systems. If you want a competitive advantage that will yield a significant savings of time and money to your customers, SubD-NURBS is the tool for you. The value of the SubDNURBS library can be viewed through several different work flow scenarios; as a NURBS Export Tool on a Sub-D System, as a Sub-D Import Tool on a NURBS System, as an enabling technology integrating Sub-D and NURBS in a hybrid modeling system. This video tutorial shows an example of how SubD-NURBS could work in a hybrid modeling system. For more information on why integration of Sub-D and NURBS is so important look at the Sub-D/NURBS Background.



NURBS Export Tool

If you have a Sub-D modeling system, you can greatly increase its usefullness within your customer's workflow by integrating the SubDNURBS library. Adding SubD-NURBS to your Sub-D based modeling system will provide unique functionality that will save your customers time and money. For example, SubD-NURBS provides the ability to export Sub-D models into standard CAD formats (in their native, precise NURBS formats). SubD-NURBS contains export tools for the most common standard NURBS formats (STEP, IGES, SAT, and Rhino's 3DM). Meshes which are closed solids will be exported as Solid Boundary Representations in these formats. Meshes which are not closed will be exported as Shell Boundary Representations. Should visual verification be required for the export process, SubD-NURBS also contains various tools for both polygonal and wireframe display of the resulting NURBS objects.


Export Workflow


With this workflow, Sub-D modeling systems can become front end freeform or conceptual design systems for Mechanical CAD and Architectural CAD systems. The freeform shape can be designed in the Sub-D system and it can be detailed in the CAD system. SubDNURBS can also facilitate the integration with FEM analysis systems by providing the mechanism to export Sub-D models into formats that most FEM analysis products can import. In a similar way, SubD-NURBS also facilitates the integration with manufacturing and rapid prototyping systems. The advantage of this workflow is that complex freeform shapes can be easily and quickly designed by artists and the result can be used directly or indirectly in the actual construction, analysis, and manufacturing of the object by engineers and designers using a CAD system.



Sub-D Mesh Import Tool

Engineers working with Mechanical CAD systems often need physical objects or human figures to complete and demonstrate their design. There are millions of 3-D polygonal models available for download either free or for a moderate fee on sites like Turbosquid. A large percentage of these models are created using Sub-D modeling techniques. SubD-NURBS does an excellent job of converting these type of models and even models with a moderate number of triangles into NURBS geometry. Instead of trying to recreate these "secondary" objects in the CAD system, they can be easily obtained from various sources (thus saving time and money).


Import Tool


For Architectural CAD systems, the importing of auxillary objects such as tables, chairs, sofas, automobiles, artwork, etc. as well as human figures is very important to give the designer a feel for the layout of the spaces being designed. Including these auxiliary objects in the design is also very important for illustartions and renderings of architectural models. Also of interest to the Architectural community is the design of more freeform structures such as those produced by Frank Gehry (as shown in the example below) lend themselves very well to Sub-D design techniques.


Gehry Building



Hybrid Modeling

Perhaps the most intriguing utilization of SubDNURBS is in that of a "Hybrid" system with both NURBS and Sub-D modeling tools. In this enviroment we can foresee a much tighter integration of the artistic design process with the engineering process. For example, the engineer may need a part of the model to be moved slightly or constructed in a slightly different way to enable the correct engineering to take place.


SubDNURBS Workflow


Because most of the CAD systems utilize a history mechanism, the Sub-D model can be modified directly and the updated result passed through the engineering operations (Boolean, feature application, filleting, etc.). This may be the optimal way to quickly get designs that are both very asthetic and very well engineered.



Sub-D/NURBS Background

There are basically two different camps in the 3-D modeling world: polygonal modeling, and NURBS modeling. The polygonal modeling camp represents everything with 3-D faceted meshes. A facet or polygonal face is typically flat and bounded line segments and/or points. Polygonal modeling is the prefered tool for 3-D artists and designers because it gives them a relatively simple set of powerful tools that allows them to model very complex shapes quickly. The advent of Subdivision Surfaces (Sub-D) has made polygonal modeling the prefered method for modeling most freeform objects for animation, conceptual automotive design, architectural design, organic models, conceptual product design and artistic design. Subdivision surface modeling is utilized by a majority of the "Computer Graphics" systems such as 3DS Max, Modo, Maya, XSI, Blender, K-3D, LightWave, Cinema 4D, etc.


The NURBS modeling camp represents everything using higher order surfaces such as cones, cylinders, spline surfaces. Nearly every CAD system has as its primary geometry representation a NURBS surface. NURBS surfaces are defined in IGES and STEP and thus are an industry standard that everyone in the CAD world works with. NURBS can be used to precisely represent freeform surfaces such as those found in airplane wing design, car body design, and ship hull design. The strength of the NURBS systems is that they support complex modeling operations such as Boolean, Fillet, Offset. These operations are required to define most manufactured parts.


Neither Sub-D modeling nor NURBS modeling is the end all, perfect, or ultimate modeling tool. Each has strengths and weaknesses. Sub-D modeling is great at producing and modifying complex freeform shapes with smooth surfaces. NURBS modeling is good at combining shapes using Boolean and Feature operations, as well as refining shapes with operations like filleting, blending and face editing. We really see SubD-NURBS as an important unification between these two camps, and a revolution in the 3D modeling design process.


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Advanced Solids
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