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92 lines
3.7 KiB
C++
92 lines
3.7 KiB
C++
/*=========================================================================
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Program: Visualization Toolkit
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Module: vtkTriangleMeshPointNormals.h
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Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
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All rights reserved.
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See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
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This software is distributed WITHOUT ANY WARRANTY; without even
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the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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PURPOSE. See the above copyright notice for more information.
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=========================================================================*/
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/**
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* @class vtkTriangleMeshPointNormals
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* @brief compute point normals for triangle mesh
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*
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* vtkTriangleMeshPointNormals is a filter that computes point normals for
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* a triangle mesh to enable high-performance rendering. It is a fast-path
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* version of the vtkPolyDataNormals filter in order to be able to compute
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* normals for triangle meshes deforming rapidly.
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*
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* The computed normals (a vtkFloatArray) are set to be the active normals
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* (using SetNormals()) of the PointData. The array name is "Normals", so
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* they can be retrieved either with `output->GetPointData()->GetNormals()`
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* or with `output->GetPointData()->GetArray("Normals")`.
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*
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* The algorithm works by determining normals for each triangle and adding
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* these vectors to the triangle points. The resulting vectors at each
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* point are then normalized.
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*
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* @warning
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* Normals are computed only for triangular polygons: the filter can not
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* handle meshes with other types of cells (Verts, Lines, Strips) or Polys
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* with the wrong number of components (not equal to 3).
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*
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* @warning
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* Unlike the vtkPolyDataNormals filter, this filter does not apply any
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* splitting nor checks for cell orientation consistency in order to speed
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* up the computation. Moreover, normals are not calculated the exact same
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* way as the vtkPolyDataNormals filter since the triangle normals are not
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* normalized before being added to the point normals: those cell normals
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* are therefore weighted by the triangle area. This is not more nor less
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* correct than normalizing them before adding them, but it is much faster.
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*
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* @sa
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* If you do not need to do high-performance rendering, you should use
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* vtkPolyDataNormals if your mesh is not only triangular, if you need to
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* split vertices at sharp edges, or if you need to check that the cell
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* orientations are consistent to flip inverted normals.
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*
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* @sa
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* If you still need high-performance rendering but your input polydata is
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* not a triangular mesh and/or does not have consistent cell orientations
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* (causing inverted normals), you can still use this filter by using
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* vtkTriangleFilter and/or vtkCleanPolyData respectively beforehand. If
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* your mesh is deforming rapidly, you should be deforming the output mesh
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* of those two filters instead in order to only run them once.
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*
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*/
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#ifndef vtkTriangleMeshPointNormals_h
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#define vtkTriangleMeshPointNormals_h
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#include "vtkFiltersCoreModule.h" // For export macro
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#include "vtkPolyDataAlgorithm.h"
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class vtkPolyData;
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class VTKFILTERSCORE_EXPORT vtkTriangleMeshPointNormals : public vtkPolyDataAlgorithm
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{
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public:
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vtkTypeMacro(vtkTriangleMeshPointNormals, vtkPolyDataAlgorithm);
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void PrintSelf(ostream& os, vtkIndent indent) override;
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static vtkTriangleMeshPointNormals* New();
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protected:
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vtkTriangleMeshPointNormals() {}
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~vtkTriangleMeshPointNormals() override {}
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// Usual data generation method
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int RequestData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) override;
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private:
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vtkTriangleMeshPointNormals(const vtkTriangleMeshPointNormals&) = delete;
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void operator=(const vtkTriangleMeshPointNormals&) = delete;
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};
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#endif
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