NAME
vtkCell - abstract class to specify cell behavior
SYNOPSIS
#include "/opt/vtk-c++/common/vtkCell.h"
class VTK_EXPORT vtkCell : public vtkObject
vtkCell();
void Initialize(int npts, int *pts, vtkPoints *p);
const char *GetClassName() {return "vtkCell";};
void PrintSelf(ostream& os, vtkIndent indent);
virtual vtkCell *MakeObject() = 0;
virtual int GetCellType() = 0;
virtual int GetCellDimension() = 0;
CAVEATS
The #define VTK_CELL_SIZE is a parameter used to construct cells and provide a general guideline for controlling object execution. This parameter is not a hard boundary: you can create cells with more points.
SEE ALSO
vtkHexahedron vtkLine vtkPixel vtkPolyLine vtkPolyVertex vtkPolygon vtkQuad vtkTetra vtkTriangle vtkTriangleStrip vtkVertex vtkVoxel
DEFINED MACROS
VTK_CELL_SIZE 512
VTK_TOL 1.e-05 // Tolerance for geometric calculation
SUMMARY
virtual vtkCell *MakeObject() = 0;
Create concrete copy of this cell.
virtual int GetCellType() = 0;
Return the type of cell.
virtual int GetCellDimension() = 0;
Return the topological dimensional of the cell (0,1,2, or 3).
virtual int GetInterpolationOrder() {return 1;}; //usually linear
Return the interpolation order of the cell.
virtual int GetNumberOfEdges() = 0;
Get the point coordinates for the cell. Return the number of points in the cell. Return the number of edges in the cell.
virtual int GetNumberOfFaces() = 0;
Return the number of faces in the cell.
virtual vtkCell *GetEdge(int edgeId) = 0;
Return the list of point ids defining the cell. For cell point i, return the actual point id. Return the edge cell from the edgeId of the cell.
virtual vtkCell *GetFace(int faceId) = 0;
Return the face cell from the faceId of the cell.
virtual int CellBoundary(int subId, float pcoords[3], vtkIdList& pts) = 0;
Given parametric coordinates of a point, return the closest cell boundary, and whether the point is inside or outside of the cell. The cell boundary is defined by a list of points (pts) that specify a face (3D cell), edge (2D cell), or vertex (1D cell). If the return value of the method is != 0, then the point is inside the cell.
virtual int EvaluatePosition(float x[3], float closestPoint[3], Given a point x[3] return inside(=1) or outside(=0) cell; evaluate parametric coordinates, sub-cell id (!=0 only if cell is composite), distance squared of point x[3] to cell (in particular, the sub-cell indicated), closest point on cell to x[3], and interpolation weights in cell. (The number of weights is equal to the number of points defining the cell). Note: on rare occasions a -1 is returned from the method. This means that numerical error has occurred and all data returned from this method should be ignored. Also, inside/outside is determine parametrically. That is, a point is inside if it satisfies parametric limits. This can cause problems for cells of topological dimension 2 or less, since a point in 3D can project onto the cell within parametric limits but be "far" from the cell. Thus the value dist2 may be checked to determine true in/out.
virtual void EvaluateLocation(int& subId, float pcoords[3], Determine global coordinate (x[3]) from subId and parametric coordinates. Also returns interpolation weights. (The number of weights is equal to the number of points in the cell.)
virtual void Contour(float value, vtkFloatScalars *cellScalars,
Generate contouring primitives. The scalar list cellScalars are scalar values at each cell point. The point locator is essentially a points list that merges points as they are inserted (i.e., prevents duplicates). Contouring primitives can be vertices, lines,
or polygons. It is possible to interpolate point data along the edge by providing input and output point data - if outPd is NULL, then no interpolation is performed.
virtual void Clip(float value, vtkFloatScalars *cellScalars, Cut (or clip) the cell based on the input cellScalars and the specified value. The output of the clip operation will be one or more cells of the same topological dimension as the original cell. The flag insideOut controls what part of the cell is considered inside normally cell points whose scalar value is greater than
"value" are considered inside. If insideOut is on, this is reversed.
virtual int IntersectWithLine(float p1[3], float p2[3], float tol, float& t,
Intersect with a ray. Return parametric coordinates (both line and cell) and global intersection coordinates, given ray definition and tolerance. The method returns non-zero value if intersection occurs.
virtual int Triangulate(int index, vtkIdList &ptIds, vtkFloatPoints &pts) = 0;
Generate simplices of proper dimension. If cell is 3D, tetrahedron are generated; if 2D triangles; if 1D lines; if 0D points. The form of the output is a sequence of points, each n+1 points (where n is topological cell dimension) defining a simplex. The index
is a parameter that controls which triangulation to use (if more than one is possible). If numerical degeneracy encountered, 0 is returned, otherwise 1 is returned.
virtual void Derivatives(int subId, float pcoords[3], float *values,
Compute derivatives given cell subId and parametric coordinates. The values array is a series of data value(s) at the cell points. There is a one-to-one correspondence between cell point and data value(s). Dim is the number of data values per cell point. Derivs are derivatives in the x-y-z coordinate directions for each data value. Thus, if computing derivatives for a scalar function in a hexahedron, dim=1, 8 values are supplied, and 3 deriv values are returned (i.e., derivatives in x-y-z directions). On the other hand, if computing derivatives of velocity (vx,vy,vz) dim=3, 24 values are supplied ((vx,vy,vz)1, (vx,vy,vz)2, ....()8), and 9 deriv values are returned ((d(vx)/dx),(d(vx)/dy),(d(vx)/dz),
char HitBBox (float bounds[6], float origin[3], float dir[3],
float coord[3], float& t)
Bounding box intersection modified from Graphics Gems Vol I. Note: the intersection ray is assumed normalized, such that valid intersections can only occur between [0,1]. Method returns non-zero value if bounding box is hit. Origin[3] starts the ray, dir[3] is the components of the ray in the x-y-z directions, coord[3] is the location of hit, and t is the parametric coordinate along line.
float *GetBounds ()
Compute cell bounding box (xmin,xmax,ymin,ymax,zmin,zmax). Return pointer to array of six float values.
void GetBounds(float bounds[6])
Compute cell bounding box (xmin,xmax,ymin,ymax,zmin,zmax). Copy result into user provided array.
float GetLength2 ()
Compute Length squared of cell (i.e., bounding box diagonal squared).