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.
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.
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)
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.
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.
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
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 .
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.