Section: Visualization Toolkit Hybrid Classes
An brief description of the algorithm is as follows. The algorithm uses a top-down decimation approach that initially represents the height field with two triangles (whose vertices are at the four corners of the image). These two triangles form a Delaunay triangulation. In an iterative fashion, the point in the image with the greatest error (as compared to the original height field) is injected into the triangulation. (Note that the single point with the greatest error per triangle is identified and placed into a priority queue. As the triangulation is modified, the errors from the deleted triangles are removed from the queue, error values from the new triangles are added.) The point whose error is at the top of the queue is added to the triangulaion modifying it using the standard incremental Delaunay point insertion (see vtkDelaunay2D) algorithm. Points are repeatedly inserted until the appropriate (user-specified) error criterion is met.
To use this filter, set the input and specify the error measure to be used. The error measure options are 1) the absolute number of triangles to be produced; 2) a fractional reduction of the mesh (numTris/maxTris) where maxTris is the largest possible number of triangles 2*(dims[0]-1)*(dims[1]-1); 3) an absolute measure on error (maximum difference in height field to reduced TIN); and 4) relative error (the absolute error is normalized by the diagonal of the bounding box of the height field).
To create an instance of class vtkGreedyTerrainDecimation, simply invoke its constructor as follows
obj = vtkGreedyTerrainDecimation
obj
is an instance of the vtkGreedyTerrainDecimation class.
string = obj.GetClassName ()
int = obj.IsA (string name)
vtkGreedyTerrainDecimation = obj.NewInstance ()
vtkGreedyTerrainDecimation = obj.SafeDownCast (vtkObject o)
obj.SetErrorMeasure (int )
- Specify how to terminate the algorithm: either as an absolute number of
triangles, a relative number of triangles (normalized by the full
resolution mesh), an absolute error (in the height field), or relative
error (normalized by the length of the diagonal of the image).
int = obj.GetErrorMeasureMinValue ()
- Specify how to terminate the algorithm: either as an absolute number of
triangles, a relative number of triangles (normalized by the full
resolution mesh), an absolute error (in the height field), or relative
error (normalized by the length of the diagonal of the image).
int = obj.GetErrorMeasureMaxValue ()
- Specify how to terminate the algorithm: either as an absolute number of
triangles, a relative number of triangles (normalized by the full
resolution mesh), an absolute error (in the height field), or relative
error (normalized by the length of the diagonal of the image).
int = obj.GetErrorMeasure ()
- Specify how to terminate the algorithm: either as an absolute number of
triangles, a relative number of triangles (normalized by the full
resolution mesh), an absolute error (in the height field), or relative
error (normalized by the length of the diagonal of the image).
obj.SetErrorMeasureToNumberOfTriangles ()
- Specify how to terminate the algorithm: either as an absolute number of
triangles, a relative number of triangles (normalized by the full
resolution mesh), an absolute error (in the height field), or relative
error (normalized by the length of the diagonal of the image).
obj.SetErrorMeasureToSpecifiedReduction ()
- Specify how to terminate the algorithm: either as an absolute number of
triangles, a relative number of triangles (normalized by the full
resolution mesh), an absolute error (in the height field), or relative
error (normalized by the length of the diagonal of the image).
obj.SetErrorMeasureToAbsoluteError ()
- Specify how to terminate the algorithm: either as an absolute number of
triangles, a relative number of triangles (normalized by the full
resolution mesh), an absolute error (in the height field), or relative
error (normalized by the length of the diagonal of the image).
obj.SetErrorMeasureToRelativeError ()
- Specify the number of triangles to produce on output. (It is a
good idea to make sure this is less than a tessellated mesh
at full resolution.) You need to set this value only when
the error measure is set to NumberOfTriangles.
obj.SetNumberOfTriangles (vtkIdType )
- Specify the number of triangles to produce on output. (It is a
good idea to make sure this is less than a tessellated mesh
at full resolution.) You need to set this value only when
the error measure is set to NumberOfTriangles.
vtkIdType = obj.GetNumberOfTrianglesMinValue ()
- Specify the number of triangles to produce on output. (It is a
good idea to make sure this is less than a tessellated mesh
at full resolution.) You need to set this value only when
the error measure is set to NumberOfTriangles.
vtkIdType = obj.GetNumberOfTrianglesMaxValue ()
- Specify the number of triangles to produce on output. (It is a
good idea to make sure this is less than a tessellated mesh
at full resolution.) You need to set this value only when
the error measure is set to NumberOfTriangles.
vtkIdType = obj.GetNumberOfTriangles ()
- Specify the number of triangles to produce on output. (It is a
good idea to make sure this is less than a tessellated mesh
at full resolution.) You need to set this value only when
the error measure is set to NumberOfTriangles.
obj.SetReduction (double )
- Specify the reduction of the mesh (represented as a fraction). Note
that a value of 0.10 means a 10% reduction. You need to set this value
only when the error measure is set to SpecifiedReduction.
double = obj.GetReductionMinValue ()
- Specify the reduction of the mesh (represented as a fraction). Note
that a value of 0.10 means a 10% reduction. You need to set this value
only when the error measure is set to SpecifiedReduction.
double = obj.GetReductionMaxValue ()
- Specify the reduction of the mesh (represented as a fraction). Note
that a value of 0.10 means a 10% reduction. You need to set this value
only when the error measure is set to SpecifiedReduction.
double = obj.GetReduction ()
- Specify the reduction of the mesh (represented as a fraction). Note
that a value of 0.10 means a 10% reduction. You need to set this value
only when the error measure is set to SpecifiedReduction.
obj.SetAbsoluteError (double )
- Specify the absolute error of the mesh; that is, the error in height
between the decimated mesh and the original height field. You need to
set this value only when the error measure is set to AbsoluteError.
double = obj.GetAbsoluteErrorMinValue ()
- Specify the absolute error of the mesh; that is, the error in height
between the decimated mesh and the original height field. You need to
set this value only when the error measure is set to AbsoluteError.
double = obj.GetAbsoluteErrorMaxValue ()
- Specify the absolute error of the mesh; that is, the error in height
between the decimated mesh and the original height field. You need to
set this value only when the error measure is set to AbsoluteError.
double = obj.GetAbsoluteError ()
- Specify the absolute error of the mesh; that is, the error in height
between the decimated mesh and the original height field. You need to
set this value only when the error measure is set to AbsoluteError.
obj.SetRelativeError (double )
- Specify the relative error of the mesh; that is, the error in height
between the decimated mesh and the original height field normalized by
the diagonal of the image. You need to set this value only when the
error measure is set to RelativeError.
double = obj.GetRelativeErrorMinValue ()
- Specify the relative error of the mesh; that is, the error in height
between the decimated mesh and the original height field normalized by
the diagonal of the image. You need to set this value only when the
error measure is set to RelativeError.
double = obj.GetRelativeErrorMaxValue ()
- Specify the relative error of the mesh; that is, the error in height
between the decimated mesh and the original height field normalized by
the diagonal of the image. You need to set this value only when the
error measure is set to RelativeError.
double = obj.GetRelativeError ()
- Specify the relative error of the mesh; that is, the error in height
between the decimated mesh and the original height field normalized by
the diagonal of the image. You need to set this value only when the
error measure is set to RelativeError.
obj.SetBoundaryVertexDeletion (int )
- Turn on/off the deletion of vertices on the boundary of a mesh. This
may limit the maximum reduction that may be achieved.
int = obj.GetBoundaryVertexDeletion ()
- Turn on/off the deletion of vertices on the boundary of a mesh. This
may limit the maximum reduction that may be achieved.
obj.BoundaryVertexDeletionOn ()
- Turn on/off the deletion of vertices on the boundary of a mesh. This
may limit the maximum reduction that may be achieved.
obj.BoundaryVertexDeletionOff ()
- Turn on/off the deletion of vertices on the boundary of a mesh. This
may limit the maximum reduction that may be achieved.
obj.SetComputeNormals (int )
- Compute normals based on the input image. Off by default.
int = obj.GetComputeNormals ()
- Compute normals based on the input image. Off by default.
obj.ComputeNormalsOn ()
- Compute normals based on the input image. Off by default.
obj.ComputeNormalsOff ()
- Compute normals based on the input image. Off by default.