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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