Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
1998-11-16
2001-06-19
Zimmerman, Mark (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
C345S420000, C345S426000, C345S428000
Reexamination Certificate
active
06249287
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of modeling a closed surface geometry and in particular to a method of modeling a closed surface geometry using a mesh having a reduced number of polygons.
Many branches of biomedical science and engineering require geometric modeling of various parts of the human body. The success of magnetic resonance imaging (MRI) and other imaging modalities of computer aided tomography have lead to many achievements in scientific visualization of parts of the human body. Typical methods based on slice data generate models containing hundreds of thousands of triangles that provide excellent details for 3D visualizations, but cannot be used directly for scientific analysis with numerical methods due to their huge size and lack of smoothness.
There exist methods that substantially reduce (more than 90%) the number of triangles in the model, but these methods are still unsatisfactory for analytical purposes. These methods were designed specifically to preserve the topology of the original geometry produced from slice data and, therefore, are subject to possible noise influence that results in holes and other irregularities of geometry.
Conventional methods do not reduce the number of triangles to a desired level. To alleviate these problems, scientists use drastically simplified models for their analysis. These models may be either spheres or cylinders of appropriate size and position. A drawback to the use of known geometry (e.g. spheres, cylinders, etc.) is that the models do not approximate the surface to be modeled with sufficient accuracy. There is a perceived need in the art for models that satisfy the requirement of computational simplicity and at the same time approximate the parts of the body more accurately than known geometry such as spheres and cylinders.
BRIEF SUMMARY OF THE INVENTION
A method for modeling an object with a polygonal mesh includes obtaining a closed-surface polygonal mesh and positioning the closed-surface polygonal mesh relative to the object. A ray is projected through a point-of-interest on the closed-surface polygonal mesh. An intersection point between the ray and a surface of the object is determined and the location of the point-of-interest is adjusted in response to the location of the intersection point. The projecting is performed for a plurality of points in the closed-surface polygonal mesh in order to approximate the object.
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Lorenson et al. “Marching Cubes: High Resolution 3D Surface Construction Algorithm” Computer Graphics, vol. 21, No. 4, Jul. 1987, pp. 163-169.
Lutkenhoner et al. “Comparison between Different Methods to Approximate and Area of the Human Head by a Sphere” Auditory Evoked Magnetic Fields and Electric Potentials, 1990, pp. 103-118.
Schroeder et al. “Decimation of Triangle Meshes” Computer Graphics, 26, 2, Jul. 1992, pp. 65-70.
General Electric Company
Santiago Enrique L
Snyder Marvin
Testa Jean K.
Zimmerman Mark
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