PlaneGeometryIntersection Class Reference

(Preview feature) [Medical] Class for computing the intersection of geometry with a plane. More...

#include <Medical/nodes/PlaneGeometryIntersection.h>

Inheritance diagram for PlaneGeometryIntersection:

Public Member Functions
virtual SoType	getTypeId () const
	Returns the type identifier for this specific instance.
const SoShape *	getShape () const
	Get the shape node that contains the computed vertices and indices.
int	recompute ()
	Recompute the intersection.
	PlaneGeometryIntersection ()
	Constructor.
Public Member Functions inherited from SoSeparator
	SoSeparator ()
	Creates a separator node with default settings.
	SoSeparator (int nChildren)
	Constructor that takes approximate number of children.
Public Member Functions inherited from SoGroup
	SoGroup ()
	Creates an empty group node.
	SoGroup (int nChildren)
	Constructor that takes approximate number of children.
virtual void	addChild (SoNode *child)
	Adds a child as last one in group.
virtual void	insertChild (SoNode *child, int newChildIndex)
	Adds a child so that it becomes the one with the given index.
virtual SoNode *	getChild (int index) const
	Returns pointer the child node with the given index.
virtual int	findChild (const SoNode *child) const
	Finds index of given child within group.
virtual int	getNumChildren () const
	Returns number of children.
virtual void	removeChild (int index)
	Removes child with given index from group.
virtual void	removeChild (SoNode *child)
	Removes first instance of given child from group.
virtual void	removeAllChildren ()
	Removes all children from group.
virtual void	replaceChild (int index, SoNode *newChild)
	Replaces child with given index with new child.
virtual void	replaceChild (SoNode *oldChild, SoNode *newChild)
	Replaces first instance of given child with new child.
Public Member Functions inherited from SoNode
virtual void	setOverride (const SbBool state)
	Turns the override flag on or off.
virtual SbBool	isOverride () const
	Returns the state of the override flag.
virtual SoNode *	copy (SbBool copyConnections=FALSE) const
	Creates and returns an exact copy of the node.
virtual void	touch ()
	Marks an instance as modified, simulating a change to it.
Public Member Functions inherited from SoFieldContainer
void	setToDefaults ()
	Sets all fields in this object to their default values.
SbBool	hasDefaultValues () const
	Returns TRUE if all of the object's fields have their default values.
SbBool	fieldsAreEqual (const SoFieldContainer *fc) const
	Returns TRUE if this object's fields are exactly equal to fc's fields.
void	copyFieldValues (const SoFieldContainer *fc, SbBool copyConnections=FALSE)
	Copies the contents of fc's fields into this object's fields.
SoNONUNICODE SbBool	set (const char *fieldDataString)
	Sets one or more fields in this object to the values specified in the given string, which should be a string in the Open Inventor file format.
SbBool	set (const SbString &fieldDataString)
	Sets one or more fields in this object to the values specified in the given string, which should be a string in the Open Inventor file format.
void	get (SbString &fieldDataString)
	Returns the values of the fields of this object in the Open Inventor ASCII file format in the given string.
virtual int	getFields (SoFieldList &list) const
	Appends references to all of this object's fields to resultList, and returns the number of fields appended.
virtual int	getAllFields (SoFieldList &list) const
	Returns a list of fields, including the eventIn's and eventOut's.
virtual SoField *	getField (const SbName &fieldName) const
	Returns a the field of this object whose name is fieldName.
virtual SoField *	getEventIn (const SbName &fieldName) const
	Returns a the eventIn with the given name.
virtual SoField *	getEventOut (const SbName &fieldName) const
	Returns the eventOut with the given name.
SbBool	getFieldName (const SoField *field, SbName &fieldName) const
	Returns the name of the given field in the fieldName argument.
SbBool	enableNotify (SbBool flag)
	Notification at this Field Container is enabled (if flag == TRUE) or disabled (if flag == FALSE).
SbBool	isNotifyEnabled () const
	Notification is the process of telling interested objects that this object has changed.
virtual void	setUserData (void *data)
	Sets application data.
void *	getUserData (void) const
	Gets user application data.
Public Member Functions inherited from SoBase
virtual SbName	getName () const
	Returns the name of an instance.
virtual void	setName (const SbName &name)
	Sets the name of an instance.
void	setSynchronizable (const bool b)
	Sets this to be a ScaleViz synchronizable object.
bool	isSynchronizable () const
	Gets the ScaleViz synchronizable state of this object.
Public Member Functions inherited from SoRefCounter
void	ref () const
	Adds a reference to an instance.
void	unref () const
	Removes a reference from an instance.
void	unrefNoDelete () const
	unrefNoDelete() should be called when it is desired to decrement the reference count, but not delete the instance if this brings the reference count to zero.
int	getRefCount () const
	Returns current reference count.
void	lock () const
	lock this instance.
void	unlock () const
	unlock this instance.
Public Member Functions inherited from SoTypedObject
SbBool	isOfType (const SoType &type) const
	Returns TRUE if this object is of the type specified in type or is derived from that type.
template<typename TypedObjectClass >
SbBool	isOfType () const
	Returns TRUE if this object is of the type of class TypedObjectClass or is derived from that class.

Static Public Member Functions
static SoType	getClassTypeId ()
	Returns the type identifier for this class.
static void	initClass ()
	Initialize class (called automatically by InventorMedical::init()).
static void	exitClass ()
	Finish using class (called automatically by InventorMedical::finish()).
Static Public Member Functions inherited from SoSeparator
static SoType	getClassTypeId ()
	Returns the type identifier for this class.
Static Public Member Functions inherited from SoGroup
static SoType	getClassTypeId ()
	Returns the type identifier for this class.
Static Public Member Functions inherited from SoNode
static SoType	getClassTypeId ()
	Returns the type identifier for this class.
static SoNode *	getByName (const SbName &name)
	A node's name can be set using SoBase::setName().
static int	getByName (const SbName &name, SoNodeList &list)
	A node's name can be set using SoBase::setName().
Static Public Member Functions inherited from SoFieldContainer
static SoType	getClassTypeId ()
	Returns the type of this class.
Static Public Member Functions inherited from SoBase
static SoType	getClassTypeId ()
	Returns type identifier for this class.
Static Public Member Functions inherited from SoTypedObject
static SoType	getClassTypeId ()
	Returns the type identifier for this class.

Public Attributes
SoSFNode	scene
	Scene to intersect with plane.
SoSFPlane	plane
	Plane to intersect with.
SoSFBool	polygon
	Specifies whether to compute a capping polygon (default false).
SoSFBool	automatic
	Specifies whether to recompute the intersection automatically or not (default true).
SoSFFloat	tolerance
	Tolerance for testing if vertices are equal.
Public Attributes inherited from SoSeparator
SoSFEnum	boundingBoxCaching
	Whether to cache during bounding box traversal.
SoSFEnum	renderCulling
	Whether to cull during rendering traversal.
SoSFEnum	pickCulling
	Whether to cull during picking traversal.
SoSFEnum	fastEditing
	Specifies the fast edit mode of the separator node.
SoSFInt32	renderUnitId
	Used during the ScaleViz depth compositing process, this field specifies which render unit (OIRU) will render the sub scene graph below this separator.
SoDEPRECATED SoSFEnum	renderCaching
	Whether to cache during rendering traversal.
Public Attributes inherited from SoGroup
SoSFBool	boundingBoxIgnoring
	Whether to ignore this node during bounding box traversal.

Additional Inherited Members
Public Types inherited from SoSeparator
enum	CacheEnabled {   OFF ,   ON ,   AUTO }
	Possible values for caching. More...
enum	FastEditing {   DISABLE = 0x01 ,   KEEP_ZBUFFER = 0x02 ,   CLEAR_ZBUFFER = 0x03 }
	Fast editing policy enumeration values. More...

Detailed Description

(Preview feature) [Medical] Class for computing the intersection of geometry with a plane.

This class computes and (optionally) renders the intersection of the geometry in the specified scene graph with the specified plane. In curve mode it computes a set of line segments corresponding to the intersection. In polygon mode it computes a set of polygon boundaries that can be used as a "cap" for clipped geometry. The intent is that the specified scene graph is one shape. In fact it can be any scene graph, but the result is always a single polygon with multiple boundaries (if necessary). The computed vertices (and indices in polygon mode) can be accessed using the getShape() method. The curve or polygon may be exported to a file like any other Open Inventor geometry using SoWriteAction, SoSTLWriteAction, etc.

Curve mode:
By default we compute and render the curve(s) defined by the intersection of the scene geometry and the plane. This is fast and works reliably for any Open Inventor geometry that produces triangles when an SoCallbackAction is applied (almost all Open Inventor geometry nodes). The appearance of the intersection curve can be controlled like any Open Inventor geometry using SoMaterial, SoDrawStyle, etc. nodes. The application may need to use an SoPolygonOffset node to "push" the scene geometry behind the intersection curve (polygon offset does not affect the intersection curve because it is a line set). Curve mode is useful to see where a clip plane intersects the geometry. Because it is much faster than polygon mode it is useful as a preview of where the polygons will be generated (if possible).

Polygon mode:
When the polygon field is set to true, the node converts the intersection curves to polygon boundaries. All the boundaries are stored in an SoIndexedFaceSet node and an SoShapeHints node is created with the 'windingType' field set to ODD_TYPE. All boundaries have counterclockwise vertex ordering and the face normal vector is the opposite of the current plane normal vector (because for a clip plane the plane normal points toward the unclipped half space which is effectively toward the interior of the shape). The appearance of the polygon can be controlled like any Open Inventor geometry using SoMaterial, etc. nodes. There are cases where polygons cannot be constructed, for example if the geometry is self-intersecting.

The coordinates of the intersection boundaries can be accessed using the getShape() method. This is an SoLineSet in curve mode and an SoIndexedFaceSet in polygon mode. In either case the coordinates are in the shape's attached SoVertexProperty node. Note that in curve mode the line segments are in random order and do not form a connected polyline. This allows the intersection geometry to be computed in minimum time and does not (visually) effect rendering. If you need the boundary(s) as a connected polyline for some purpose, use the polygon mode. Note that in polygon mode there are redundant vertices in the vertex list because it still contains all the line segments. To follow the boundaries in connection order use the coordinate indices in the SoIndexedFaceSet node.

Notes:

• Multiple boundaries in polygon mode.
  Currently does not test if whether multiple boundaries are "holes" or "islands". Rendering should be correct in either case, but eventually some optimization could be done if all boundaries are disjoint.
• Memory.
  Memory allocated for vertices and indices is re-used on each recomputation and is not freed until the node is destroyed. This is best for performance. Eventually there should be a method to force memory to be freed.

Limitations:

• Valid geometry.
  For polygon mode to work correctly, the geometry must obey the same rules as a valid STL geometry. In particular the geometry must form a closed solid and must not be self-intersecting. All the intersection boundaries must be closed and must not intersect any other boundary.
  However in curve mode, there are no limitations. For example, the node can be used to render the intersection of a surface with a plane.
• Triangulation of the polygon.
  This node simply computes the intersection boundary(s). For rendering it relies on Open Inventor to convert the polygon to triangles. In many cases the resulting triangles have a poor (large) aspect ratio.
• Floating point precision.
  Curve mode should work reasonably well with any geometry and any coordinates. However constructing polygon boundaries is very sensitive to floating point precision problems. If the results are not good, try adjusting the tolerance value.
• Redundant coordinates.
  In polygon mode the SoVertexProperty node contains all the coordinates computed for the intersection line segments. The SoIndexedFaceSet node only indexes a subset of these vertices (typically about half). Not removing the unused vertices saves time and has no effect on rendering. To get only the coordinates that are actually used, extract vertices based on the index values in the SoIndexedFaceSet node. Eventually could be an option.
• Performamce.
  This is currently a "brute force" implementation and performance could be better.

FILE FORMAT/DEFAULT

PlaneGeometryIntersection {

scene	NONE
plane	1 0 0 0
polygon	FALSE
automatic	TRUE
tolerance	1e-6

}

SEE ALSO

InventorMedical, SoClipPlane, SoClipPlaneManip, SoSTLWriteAction

Definition at line 142 of file PlaneGeometryIntersection.h.

Constructor & Destructor Documentation

PlaneGeometryIntersection()

PlaneGeometryIntersection::PlaneGeometryIntersection

(

)

Constructor.

Member Function Documentation

exitClass()

static void PlaneGeometryIntersection::exitClass ( )

static

Finish using class (called automatically by InventorMedical::finish()).

getClassTypeId()

static SoType PlaneGeometryIntersection::getClassTypeId ( )

static

Returns the type identifier for this class.

getShape()

const SoShape * PlaneGeometryIntersection::getShape

(

)

const

Get the shape node that contains the computed vertices and indices.

Returns null if no shape has been computed yet. In curve mode this is an SoLineSet. In polygon mode this is an SoIndexedFaceSet. In both cases the vertices are in the shape node's attached SoVertexProperty node's 'vertex' field.

The application must not modify these nodes.

getTypeId()

virtual SoType PlaneGeometryIntersection::getTypeId ( ) const

virtual

Returns the type identifier for this specific instance.

Reimplemented from SoSeparator.

initClass()

static void PlaneGeometryIntersection::initClass ( )

static

Initialize class (called automatically by InventorMedical::init()).

recompute()

int PlaneGeometryIntersection::recompute

(

)

Recompute the intersection.

Recomputes the intersection boundary(s) based on the current scene and plane. Normally used when the automatic field is set to false. Useful when the goal is simply to compute the intersection. Also useful if recomputation is too slow. For example, to defer recomputation until the user has finished moving the clip plane.

Returns 0 if successful. Any other value means that an error occured during the computation and the geometry may not be valid.

Member Data Documentation

automatic

SoSFBool PlaneGeometryIntersection::automatic

Specifies whether to recompute the intersection automatically or not (default true).

If true, the intersection (curve or polygon depending on the polygon field) will be re-computed automatically when the scene or the plane changes. If false, the intersection will only be re-computed when the recompute method is called.

Definition at line 167 of file PlaneGeometryIntersection.h.

plane

SoSFPlane PlaneGeometryIntersection::plane

Plane to intersect with.

Default is (1,0,0) at 0 (same as SoClipPlane). Typically this field is connected from the clipping node's 'plane' field.

Definition at line 155 of file PlaneGeometryIntersection.h.

polygon

SoSFBool PlaneGeometryIntersection::polygon

Specifies whether to compute a capping polygon (default false).

If true, compute a capping polygon. If false, compute only the intersection curve.

Definition at line 160 of file PlaneGeometryIntersection.h.

scene

SoSFNode PlaneGeometryIntersection::scene

Scene to intersect with plane.

Default is none.

Definition at line 149 of file PlaneGeometryIntersection.h.

tolerance

SoSFFloat PlaneGeometryIntersection::tolerance

Tolerance for testing if vertices are equal.

Default is 1e-6. This tolerance is used for calculation of triangle intersections with the plane.

Definition at line 173 of file PlaneGeometryIntersection.h.

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

• Medical/nodes/PlaneGeometryIntersection.h