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Public Member Functions | Static Public Member Functions | Public Attributes | Protected Member Functions

SoNurbsProfile Class Reference

The SoNurbsProfile class is a node for specifying smooth profile curves.Use nodes of this type if you want to set up profiles that are smooth curves. More...

#include <Inventor/nodes/SoNurbsProfile.h>

Inheritance diagram for SoNurbsProfile:
SoProfile SoNode SoFieldContainer SoBase

List of all members.

Public Member Functions

 SoNurbsProfile (void)
virtual void getTrimCurve (SoState *state, int32_t &numpoints, float *&points, int &floatspervec, int32_t &numknots, float *&knotvector)
virtual void getVertices (SoState *state, int32_t &numvertices, SbVec2f *&vertices)

Static Public Member Functions

static void initClass (void)

Public Attributes

SoMFFloat knotVector

Protected Member Functions

virtual ~SoNurbsProfile ()

Detailed Description

The SoNurbsProfile class is a node for specifying smooth profile curves.

Use nodes of this type if you want to set up profiles that are smooth curves.

A typical usage case for SoNurbsProfile is to specify NURBS trimming curves. For example:

  #Inventor V2.1 ascii

  ShapeHints {
    vertexOrdering COUNTERCLOCKWISE
  }

  Coordinate3 {
    point [ 
      -3 -3 -3, -3 -1 -3, -3 1 -3, -3 3 -3,
      -1 -3 -3, -1 -1  3, -1 1  3, -1 3 -3,
       1 -3 -3,  1 -1  3,  1 1  3,  1 3 -3,
       3 -3 -3,  3 -1 -3,  3 1 -3,  3 3 -3
     ]
  }

  ProfileCoordinate2 {
    point [ 0.0 0.0 ,
            0.75 0.0,
            0.75 0.75 ,
            0.25 0.75 ,
            0.0 0.0  ]
  }

  NurbsProfile {
     index [ 0 , 1 , 2 , 3, 4 ]
     linkage START_NEW
     knotVector [ 0, 0, 0, 0, 0.5, 1, 1, 1, 1 ]
  }

  NurbsSurface {
    numUControlPoints 4
    numVControlPoints 4
    uKnotVector [ 0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.0, 1.0 ]
    vKnotVector [ 0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.0, 1.0 ]
  }
nurbsprofile.png

Note that the coordinates of the NurbsProfile live in the parametric space of the trimmed SoNurbsSurface, and that the same complexity setting (which is calculated based on the dimensions of the bounding box of the nurbs surface) is used to determine the sampling tolerance both for the SoNurbsSurface and the SoNurbsProfile.

This means that if you want to change the tessellation of the trimming curve itself (i.e. increase or decrease the resolution of the boundaries of the "cut-out"), you should not change the SoComplexity setting but rather adapt the parametric scale in relation to the trimmed surface.

As an example, to increase the resolution of the curve in the above example, replace...

  ProfileCoordinate2 {
    point [ 0.0 0.0, 0.75 0.0, 0.75 0.75, 0.25 0.75, 0.0 0.0 ]
  }

.. with...

  ProfileCoordinate2 {
    point [ 0.0 0.0, 7.5 0.0, 7.5 7.5, 2.5 7.5, 0.0 0.0 ]
  }

and change the uKnotVector and vKnotVector of the NurbsSurface to be

    uKnotVector [ 0.0, 0.0, 0.0, 0.0, 10, 10, 10, 10 ]
    vKnotVector [ 0.0, 0.0, 0.0, 0.0, 10, 10, 10, 10 ]

However, keep in mind that increasing the accuracy of the trimming curve results in a much more complex tesselation of the trimmed surface. As a general rule of thumb, the extent of the trimming curve coordinates should never be greater than its "real" extents in relation to the trimmed surface, and often can be much lower.

If you find the above confusing, you probably do not want to use NURBS without reading up on the general concepts first. An explanation of NURBS is beyond the scope of the Coin documentation; for detailed information, refer to the specialized literature on the topic (for example "An Introduction to NURBS: With Historical Perspective" by David F. Rogers). A basic overview of curve and surface rendering using NURBS can also be found in chapter 8 of "The Inventor Mentor".

FILE FORMAT/DEFAULTS:

    NurbsProfile {
        index 0
        linkage START_FIRST
        knotVector 0
    }

Constructor & Destructor Documentation

SoNurbsProfile::SoNurbsProfile ( void  )

Constructor.

References knotVector.

SoNurbsProfile::~SoNurbsProfile ( ) [protected, virtual]

Destructor.


Member Function Documentation

void SoNurbsProfile::initClass ( void  ) [static]

Sets up initialization for data common to all instances of this class, like submitting necessary information to the Coin type system.

Reimplemented from SoProfile.

void SoNurbsProfile::getTrimCurve ( SoState state,
int32_t &  numpoints,
float *&  points,
int &  floatspervec,
int32_t &  numknots,
float *&  knotvector 
) [virtual]
void SoNurbsProfile::getVertices ( SoState state,
int32_t &  numvertices,
SbVec2f *&  vertices 
) [virtual]

Member Data Documentation

Knot values for the nurbs curve.

Referenced by getTrimCurve(), and SoNurbsProfile().


The documentation for this class was generated from the following files:

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