NAME
SoNurbsSurface -
The SoNurbsSurface class is used to render smooth surfaces.
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/SoNurbsSurface.h>
Inherits SoShape.
Public Member Functions
SoNurbsSurface (void)
virtual void GLRender (SoGLRenderAction *action)
virtual void rayPick (SoRayPickAction *action)
virtual void getPrimitiveCount (SoGetPrimitiveCountAction *action)
void sendPrimitive (SoAction *, SoPrimitiveVertex *)
Static Public Member Functions
static void initClass (void)
Public Attributes
SoSFInt32 numUControlPoints
SoSFInt32 numVControlPoints
SoSFInt32 numSControlPoints
SoSFInt32 numTControlPoints
SoMFFloat uKnotVector
SoMFFloat vKnotVector
SoMFFloat sKnotVector
SoMFFloat tKnotVector
Protected Member Functions
virtual ~SoNurbsSurface ()
virtual void generatePrimitives (SoAction *action)
virtual void computeBBox (SoAction *action, SbBox3f &box, SbVec3f
¢er)
SoDetail * createTriangleDetail (SoRayPickAction *action, const
SoPrimitiveVertex *v1, const SoPrimitiveVertex *v2, const
SoPrimitiveVertex *v3, SoPickedPoint *pp)
Detailed Description
The SoNurbsSurface class is used to render smooth surfaces.
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 surface 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.)
A basic usage 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
]
}
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 ]
}
FILE FORMAT/DEFAULTS:
NurbsSurface {
numUControlPoints 0
numVControlPoints 0
numSControlPoints 0
numTControlPoints 0
uKnotVector 0
vKnotVector 0
sKnotVector 0
tKnotVector 0
}
Constructor & Destructor Documentation
SoNurbsSurface::SoNurbsSurface (void) Constructor.
SoNurbsSurface::~SoNurbsSurface () [protected, virtual] Destructor.
Member Function Documentation
void SoNurbsSurface::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 SoShape.
void SoNurbsSurface::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 SoNurbsSurface::rayPick (SoRayPickAction * action) [virtual]
Calculates picked point based on primitives generated by subclasses.
Reimplemented from SoShape.
void SoNurbsSurface::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 SoNurbsSurface::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 SoNurbsSurface::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 SoNurbsSurface::computeBBox (SoAction * action, SbBox3f & box, SbVec3f
& center) [protected, virtual] Calculates the bounding box of all
control points, and sets the center to the average of these points.
Implements SoShape.
SoDetail * SoNurbsSurface::createTriangleDetail (SoRayPickAction * action,
const SoPrimitiveVertex * v1, const SoPrimitiveVertex * v2, const
SoPrimitiveVertex * v3, SoPickedPoint * pp) [protected, virtual] Will
create triangle 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 SoNurbsSurface::numUControlPoints Number of control points in the
U direction.
SoSFInt32 SoNurbsSurface::numVControlPoints Number of control points in the
V direction.
SoSFInt32 SoNurbsSurface::numSControlPoints Number of control points in the
S direction.
SoSFInt32 SoNurbsSurface::numTControlPoints Number of control points in the
T direction.
SoMFFloat SoNurbsSurface::uKnotVector The Bezier knot vector for the U
direction.
SoMFFloat SoNurbsSurface::vKnotVector The Bezier knot vector for the V
direction.
SoMFFloat SoNurbsSurface::sKnotVector The Bezier knot vector for the S
direction.
SoMFFloat SoNurbsSurface::tKnotVector The Bezier knot vector for the T
direction.
Author
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