Provided by: libcoin80-doc_3.1.4~abc9f50-4ubuntu2_all 
NAME
SoNurbsCurve -
The SoNurbsCurve class is a node for representing smooth curves.
A general 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 be found in chapter 8 of 'The Inventor
Mentor'.
SYNOPSIS
#include <Inventor/nodes/SoNurbsCurve.h>
Inherits SoShape.
Public Member Functions
virtual SoType getTypeId (void) const
Returns the type identification of an object derived from a class inheriting SoBase.
This is used for run-time type checking and 'downward' casting.
SoNurbsCurve (void)
virtual void GLRender (SoGLRenderAction *action)
virtual void rayPick (SoRayPickAction *action)
virtual void getPrimitiveCount (SoGetPrimitiveCountAction *action)
virtual void getBoundingBox (SoGetBoundingBoxAction *action)
void sendPrimitive (SoAction *, SoPrimitiveVertex *)
Static Public Member Functions
static SoType getClassTypeId (void)
static void initClass (void)
Public Attributes
SoSFInt32 numControlPoints
SoMFFloat knotVector
Protected Member Functions
virtual const SoFieldData * getFieldData (void) const
virtual ~SoNurbsCurve ()
virtual void generatePrimitives (SoAction *action)
virtual void computeBBox (SoAction *action, SbBox3f &box, SbVec3f ¢er)
virtual SoDetail * createLineSegmentDetail (SoRayPickAction *action, const
SoPrimitiveVertex *v1, const SoPrimitiveVertex *v2, SoPickedPoint *pp)
Static Protected Member Functions
static const SoFieldData ** getFieldDataPtr (void)
Additional Inherited Members
Detailed Description
The SoNurbsCurve class is a node for representing smooth curves.
A general 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 be found in chapter 8 of 'The Inventor
Mentor'.
Note that knot values should be specified as [0, 1, 2,..., a] rather than [0, 1/a,
2/a,..., 1] to avoid tesselation errors due to floating point precision problems. (Even if
the rendered curve looks correct, such issues might surface when e.g. doing picking, since
the tesselated representation used internally is not the same as the one you see rendered
by OpenGL on-screen.)
Each control point has a weight that changes the shape of its basis function. Weight is
analogous to having magnets pulling on the curve. Coordinate3 sets control points to have
an equal weight of 1.0 (nonrational). Use Coordinate4 to specify x, y, z and weight values
(rational).
A small usage example (drawing a circle using a rational curve):
#Inventor V2.1 ascii
Coordinate4 {
point [
0.0 -5.0 0.0 1.0,
2.5 -2.5 0.0 0.5,
2.5 -0.66987 0.0 1.0,
0.0 1.94013 0.0 0.5,
-2.5 -0.66987 0.0 1.0,
-2.5 -2.5 0.0 0.5,
0.0 -5.0 0.0 1.0
]
}
NurbsCurve {
numControlPoints 7
knotVector [ 0, 0, 0, 1, 1, 2, 2, 3, 3, 3 ]
}
# debug: show all the control points
BaseColor { rgb 1 1 0 }
DrawStyle { pointSize 3 }
PointSet { numPoints 7 }
FILE FORMAT/DEFAULTS:
NurbsCurve {
numControlPoints 0
knotVector 0
}
Constructor & Destructor Documentation
SoNurbsCurve::SoNurbsCurve (void)
Constructor.
SoNurbsCurve::~SoNurbsCurve () [protected], [virtual]
Destructor.
Member Function Documentation
SoType SoNurbsCurve::getTypeId (void) const [virtual]
Returns the type identification of an object derived from a class inheriting SoBase. This
is used for run-time type checking and 'downward' casting. Usage example:
void foo(SoNode * node)
{
if (node->getTypeId() == SoFile::getClassTypeId()) {
SoFile * filenode = (SoFile *)node; // safe downward cast, knows the type
}
}
For application programmers wanting to extend the library with new nodes, engines,
nodekits, draggers or others: this method needs to be overridden in all subclasses. This
is typically done as part of setting up the full type system for extension classes, which
is usually accomplished by using the pre-defined macros available through for instance
Inventor/nodes/SoSubNode.h (SO_NODE_INIT_CLASS and SO_NODE_CONSTRUCTOR for node classes),
Inventor/engines/SoSubEngine.h (for engine classes) and so on.
For more information on writing Coin extensions, see the class documentation of the
toplevel superclasses for the various class groups.
Reimplemented from SoShape.
const SoFieldData * SoNurbsCurve::getFieldData (void) const [protected], [virtual]
Returns a pointer to the class-wide field data storage object for this instance. If no
fields are present, returns NULL.
Reimplemented from SoShape.
void SoNurbsCurve::GLRender (SoGLRenderAction *action) [virtual]
Action method for the SoGLRenderAction.
This is called during rendering traversals. Nodes influencing the rendering state in any
way or who wants to throw geometry primitives at OpenGL overrides this method.
Reimplemented from SoShape.
void SoNurbsCurve::rayPick (SoRayPickAction *action) [virtual]
Calculates picked point based on primitives generated by subclasses.
Reimplemented from SoShape.
void SoNurbsCurve::getPrimitiveCount (SoGetPrimitiveCountAction *action) [virtual]
Action method for the SoGetPrimitiveCountAction.
Calculates the number of triangle, line segment and point primitives for the node and adds
these to the counters of the action.
Nodes influencing how geometry nodes calculates their primitive count also overrides this
method to change the relevant state variables.
Reimplemented from SoShape.
void SoNurbsCurve::getBoundingBox (SoGetBoundingBoxAction *action) [virtual]
Redefined to notify open caches that this shape contains lines.
Reimplemented from SoShape.
void SoNurbsCurve::sendPrimitive (SoAction *, SoPrimitiveVertex *)
This method is part of the original SGI Inventor API, but not implemented in Coin, as it
looks like a method that should probably have been private in Open Inventor.
void SoNurbsCurve::generatePrimitives (SoAction *action) [protected], [virtual]
The method implements action behavior for shape nodes for SoCallbackAction. It is invoked
from SoShape::callback(). (Subclasses should not override SoNode::callback().)
The subclass implementations uses the convenience methods SoShape::beginShape(),
SoShape::shapeVertex(), and SoShape::endShape(), with SoDetail instances, to pass the
primitives making up the shape back to the caller.
Implements SoShape.
void SoNurbsCurve::computeBBox (SoAction *action, SbBox3f &box, SbVec3f ¢er) [protected],
[virtual]
Calculates the bounding box of all control points, and sets the center to the average of
these points.
Implements SoShape.
SoDetail * SoNurbsCurve::createLineSegmentDetail (SoRayPickAction *action, const
SoPrimitiveVertex *v1, const SoPrimitiveVertex *v2, SoPickedPoint *pp) [protected],
[virtual]
Will create line detail for a SoPickedPoint. This method will only be called internally,
when generatePrimitives() is used for picking (SoShape::rayPick() is not overridden).
This method returns NULL in Open Inventor, and subclasses will need to override this
method to create details for a SoPickedPoint.
This is not necessary with Coin. Of course, if you choose to override it, it will work in
the same way as Open Inventor.
For this to work, you must supply a face or line detail when generating primitives. If you
supply NULL for the detail argument in SoShape::beginShape(), you'll have to override this
method.
Reimplemented from SoShape.
Member Data Documentation
SoSFInt32 SoNurbsCurve::numControlPoints
Number of control points to use in this NURBS curve.
SoMFFloat SoNurbsCurve::knotVector
The knot vector.
Values should be specified as [0, 1, 2,..., a] rather than [0, 1/a, 2/a,..., 1] to avoid
tesselation errors due to floating point precision problems.
Author
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