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w_rt_pc_phse_1.jpg (194411 bytes) The scans on the left were taken with the Minolta VIVID 700 non-contact 3-D digitizer.  It's a portable but stationary scanner that utilizes projected laser stripe technology for the scanning of 3-D exterior surfaces.  The VIVID 700 is as easy to operate as a camera and is often referred to as a 3-D camera.  The first phase of all 3-D digitizing is the point cloud phase.  The points represent the exact position of the scanned surfaces in 3-D space.  Because the VIVID 700 is a stationary scanner multiple views of the object must be scanned individually and then merged together for post processing.   These scans represent the first phase of a partial 3-D head scan.

 

w_rt_pc_phse_2.jpg (120404 bytes) The post processing of point cloud data requires specialized software.  There are a variety of software packages available for the post processing of 3-D scanned data.  As with everything you get what you pay for and the most sophisticated packages which facilitate the processing of point cloud data into nurbs compatible files are extremely expensive.   Relentless surfing of the web and the RP-ML (Rapid Prototyping - List Serve) directed me to the Beta Testing program sponsored by GeoMagic.  Geomagic's Wrap is an industry standard post processing program for 3-D scanned data.

The merged point cloud data represents the merging of the initial 3 scanned views seen in the first frame of the process description.  As you can see from the merged view and the separated views the scanned data is less than perfect.   The point manipulation phase with in Wrap facilitates the re-adjusting of points for  better surfacing.  Unfortunately, this function even proves to be extremely difficult to control the exact positioning of the thousands of unaligned points.  The challenge of 3-D digitizing is to capture adequate detail and resolution for the final 3-D digital model is directly dependent upon the scanned data for accuracy.    There's literally hundreds of thousands of points generated from a 3-D scan and if those points aren't in the correct positions it means all of those points must be edited and this is not only a tedious process but difficult because there's no exact reference points to guide the points into position.

w_rt_wrap.jpg (63699 bytes) After hours and hours of unsuccessful point manipulation and even though most documentation advised against direct polygonal surface editing I decided to surface the model anyway and attempt to edit the polygonal surface in a polygonal 3-D modeling program.  In this process I lost some accuracy but saved time and my sanity.  My other choice would've have been to have new scans taken but this wasn't an option.  There are very few scanning facilities on the east coast and the contacts I did have for scanning moved onto different areas.  The fact that this experiment succeeded is proof that with enough trial and error anything is possible if you put your mind to it.  

Essentially the surfacing phase within Geomagic Wrap blankets the point cloud data with a polygonal surface.  At this point I exported the polygonal model in several compatible formats for importing into Light Wave (a 3-D polygonal modeling) program.

w_rt_surf_adjust.jpg (82673 bytes) In Light Wave I proceeded to cut the polygonal surface in half...this facilitated the surface editing process.  I went on to smooth and in some instances rebuild the problem areas on both halves.  I then exported the halves separately for surface thickening and spline generation in Geomagic Wrap.
w_rt_splines_1.jpg (111765 bytes) The Spline Module of Geomagic Wrap facilitates the creation of B-splines on the top of the polygonal model and outputs the splines in file formats that can be imported into other programs.   The spline curves can then be used for generating NURB surfaces in other programs or for tool path planning in CAM applications. 

In Geomagic Wrap Splines can only be created for closed surfaces so if the surface isn't closed it must go through a surface thickening process for the spline phase  module to work effectively.  In the images to the left you can see the results of this thickening process.

w_rt_splines_2.jpg (135152 bytes) After the model is thickened the Spline Phase process can begin.  Only the closed or thickened surfaces of the model will be shown when you enter this phase and a set of viewing axes will be drawn.  The viewing axes assist in orienting the model correctly.  The splines are created in Geomagic Wrap by sweeping a slicing plane in a user-defined direction producing the specified number of slices.  The model is then sliced in equally spaced planes in the given direction.  For each plane a spline curve is computed, resulting in a set of parallel spline curves.  The splines can then be saved in the IGES file format and imported into many 3D modeling programs .
w_rt_nurb_template.jpg (304398 bytes) The final step in this process was to create a nurbs surfaced template that I could then build upon and edit in a 3D modeling program,  For this step I imported the Geomagic Wrap generated B-splines into RHINO, a nurbs based 3D modeling program.  Because the splines generated by Geomagic Wrap were formed around the thickened surface I had to edit each spline individually.  Only the front half of each spline was utilized for the final surfacing process.  Once the splines were divided and the number of control points for each spline verified and matched the splines were lofted in sections to create a nurbs surface.   This surface was then used for the creation of the objects in the Gallery section of this web site.

 

 

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