NAME
SoNurbsProfile -
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.
SYNOPSIS
#include <Inventor/nodes/SoNurbsProfile.h>
Inherits SoProfile.
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 ]
}
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 ]
}
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.
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] Return points and knotvector of the state.
Implements SoProfile.
void SoNurbsProfile::getVertices (SoState * state, int32_t & numvertices,
SbVec2f *& vertices) [virtual] Return vertex set of state.
Implements SoProfile.
Member Data Documentation
SoMFFloat SoNurbsProfile::knotVector Knot values for the nurbs curve.
Author
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