ISurface.InterpolateShape Method

Interpolates z values for a defined geometric shape.

[Visual Basic .NET]
Public Sub InterpolateShape ( _
    ByVal pShape As IGeometry, _
    ByRef ppOutShape As IGeometry, _
    [ByRef pStepSize As Object] _
)

[C#]
public void InterpolateShape (
    IGeometry pShape,
    ref IGeometry ppOutShape,
    ref object pStepSize
);

[C++]
HRESULT InterpolateShape(
  IGeometry* pShape,
  IGeometry** ppOutShape,
  VARIANT* pStepSize
);

[C++]
Parameters
pShape [in]
  pShape is a parameter of type IGeometry
ppOutShape [out]
  ppOutShape is a parameter of type IGeometry
pStepSize [optional]
  pStepSize is a parameter of type VARIANT
  To indicate this parameter is undefined pass a reference to a VARIANT with type VT_ERROR and scode value of DISP_E_PARAMNOTFOUND.

Product Availability

Description

The Shape is an input 2D geometry. The method interpolates heights for it from the surface, and outputs the result as 3D geometry into OutShape.

The input geometry can be a point, polyline or polygon. Portions of the input not falling within the interpolation zone of the surface will be clipped. A NULL pointer ('Nothing' in VisualBasic) is returned when the input falls entirely off the surface.

If specified, input polylines and polygons will be densified by the stepSize. This takes place before interpolating heights from the surface. The densification ensures no two vertices are spaced more than stepSize apart.

The stepSize argument isn't very important when the surface is a TIN as the default sampling scheme of using input vertices and triangle edge intersections is sufficient to capture all surface information. If the surface is a raster it becomes more important. Generally, the smaller the interval the greater the detail (unless smaller than 1/2 cellsize), but at an increased cost in processing time and size of resulting geometry. The default stepSize for raster based surface is set equal to the cellsize.

InterpolateShape will handle differences in spatial reference between the input shape and the surface. It will project (a copy of) the input geometry to match the surface for the sake of interpolation. It will then re-project the output geometry so it's the same as the input shape.

Notes:

• On rasters, bilinear interpolation is used.
• If the surface is a raster stepSize should be considered. Generally, the smaller the interval the more detail that gets captured (unless smaller than 1/2 cellsize), but at an increased cost in processing time and size of resulting geometry. The default stepSize for raster based surface is set equal to the cellsize.
• On TINs the method of interpolation is controlled by ITinSurface3.InterpolationMethod.
• On TINs, if the interpolation meethod is linear, ITinSurface3.ProfileWeedTolerance may be useful in preventing oversampled output.
• On TINs, if the interpolation method is linear, the stepSize argument isn't very important since the default sampling scheme of using input vertices and triangle edge intersections is sufficient to capture all surface information. The use of stepSize is more relevant when the interpolation method is something other than linear.

See Also