Command Line CCB_Tools_MeiheXu_SurfaceExtractionTutorialUsage

Command Line Usage

Print a usage summary to the console output.

Measure the curvature of a surface saved in a Minc OBJ file and save the curvature values into a text file

Find curvature of a Ucf file and writes a copy of the input file with curvature appended as a Ucf '4D' attribute

Find curvature of a Ucf file and writes a copy of the input file with curvature appended as a DX file:

Common Runtime Errors:

Data formats supported

Curvature algorithms

Usage

Print a usage summary to the console output.

Ucf Curvature

Print a summary of how to use the ShapeCurvature program

Measure the curvature of an Obj surface and save the curvature values into a text file

• saves curvatures at each vertex into ascii text file.

• saves as a ucf file.

Detailed Description of the program

Curvature algorithms

Discrete Gaussian Curvature

The diference of 2 PI and sum of the angles between adjacent faces adjoining the vertex C(vertex).
2Pi - a1 - a2 - a3 -...-an where n is the number of faces adjoining the vertex, and a1,...,an are the angles on the faces.
At each vertex we consider the angles formed on the adjacent faces at that corner. If the sum of these angles is exactly 360 degreee then the collection of faces can be flattened to the plane withough a gap and without any overlap. Therefore, it has zero curvature. If the sume of the angle is smaller than 360 degree then the situation is like that at the tip of a cone, or at the corner of a convex polyhedron. Here the curvature should be positive since such a polyhedron is similar to a round ball. Negative curvature arises if the sum of the angles is bgger than 360 degreee which happens, for example, at a saddle point.

data formats supported

System requirements -

Limitations -

• Speed - The method operate fast only on triangular meshes (surface made of triangular faces), all other surface methes with other elemet types take long time.
• Output - The output type must match the type of input file. Only UCF files are presently supported. In another word, Ucf files may be written as Ucf fileThe, and curvatures of all other file types may only be written as text.

Future Work -

• Improve speed - Surface meshes with other element types or mixed mesh type muse be preprocessed before the methos can be applied to them, by doing so improve speed.
• Add more curvature measurements.
• Add more shape input/output file formats.

error handling

No input or output file

if both input file and output file are not provided,then the application will be terminated.

Not appropriate input file

if input file doesn't exit or cannot be read, then the application wlll be terminated.

Not appropriate output file

if it is not possible to write output file, then the application will be terminated.

Not appropriate output type

if input file type doesn't match output type, then the application will be terminated.

Not appropriate shape

if shape has no face set or shpae has no face, then the application will be terminated.

Wrong curvature value

if the shape is open shape, some of curvature values in the output will not be correct.

• Add more shape file formats.

Error One

describe error 1 here

Errro 2

describe error 2 here

• Speed - Surfaces triangular faces surface made of triangular faces. The method operate fast only on triangular meshes, all other surface methes with other elemet type take lone time.
• Output - The output type must match the type of input file. Only UCF files are presently supported.

Usage Summary

• Basic: The command line follows this pattern: "java -jar {options} input_file output_file".
• A complete list of all command line options:
  • "-version" prints a version string to the standard output.
  • "-help" print a usage summary.
  • "-curvature sumAngle" selects the simple curvature measure.
  • "-output output_type" selects the type of output file that will be written. The default value is set as text.
  • "-infinity value" - sets the absolute value of the number used to indicate infinite curvature at a point.
  • "-output_attribute attribute_name" - sets name of attribute in output file used to store the curvature values, if possible. If the output file format does not support named attributes this parameter value is ignored. The default value is "curvature"
  • "-verbose" - enables detailed status messages during calculations.
  • "-examples" prints examples of how this program might be used.

• Curvature algorithms
  • Discrete Gaussian Curvature: The discrete Gauss curvature measures the bending of a polyhedral surface at each of its vertices. At each vertex we consider the angles formed on the adjacent faces at that corner. If the sum of these angles is exactly 360 degreee then the collection of faces can be flattened to the plane withough a gap and without any overlap. Therefor, it has zero curvature. If the sume of the angle is smaller than 360 degree then the situation is like at the tip of a cone, or at the corner of a convex polyhedron. Here the curvature should be positive since such a polyhedron is similar to a round ball. Negative curvature arises if the sum of the angles is bgger than 360 degreee which happens, for example, at a saddle point. In general, the discrete Gauss curature at a vertex is defined as the diference of 2 PI and sum of the angles between adjacent faces adjoining the vertex C(vertex) = 2Pi - a1 - a2 - a3 -...-an where n is the number of faces adjoining the vertex, and a1,...,an are the angels on the faces.

• The algorithm used in the application: Calculaes curvatures of a surface defined by the faces of an IFaceSet^?. Computes a curvagture based on the sum of the angles between vertices that are econneted to a given vertex. The algorithm is follwoing:
  • Obtain all faces which are connected to a given points, and set angleSum to be zero.
  • Using a for loop, go over each face.
  • For each face, using another for loop, find two verties that connected to the given points.
  • Construct two vectors that starting at the given point and ending at the two verties found at the previous step.
  • Calculate angle between two vectors and add to angleSum.
  • If any face remains, go back to the step 3. Otherwise we complete calculating curvature.

• error handlinge - lists the types of errors that can happen and how the program handles these errors
• data formats supported - lists the input and output data types that are supported. for each of these describe how the program handles any specific details of the data format. Describe any problems that may be encoountered (example: Ucf that is not surface mesh) and how the program responds to them. Describe any required pre-conditions for each data format.
  • Supporting input files: a) ucf. b) obj. c) off
  • Supporting output files: a) txt b) ucf

• Processor - 600 MHz Pentium chip or better
• Operating System - Any OS that has Java
• Memory - 512 Mb
• Disk Space -
• Software - Java 2(Runtime or SDK) version 1.3.1 or later

Limitation -