SoShapeHints Class Reference

Node that provides hints about shapes. More...

#include <Inventor/nodes/SoShapeHints.h>

Inheritance diagram for SoShapeHints:

Public Types
enum	VertexOrdering {   UNKNOWN_ORDERING = SoShapeHintsElement::UNKNOWN_ORDERING ,   CLOCKWISE = SoShapeHintsElement::CLOCKWISE ,   COUNTERCLOCKWISE = SoShapeHintsElement::COUNTERCLOCKWISE }
	Hints about ordering of face vertices: if ordering of all vertices of all faces is known to be consistent when viewed from "outside" shape or not. More...
enum	ShapeType {   UNKNOWN_SHAPE_TYPE = SoShapeHintsElement::UNKNOWN_SHAPE_TYPE ,   SOLID = SoShapeHintsElement::SOLID }
	Hints about entire shape: if shape is known to be a solid object, as opposed to a surface. More...
enum	FaceType {   UNKNOWN_FACE_TYPE = SoShapeHintsElement::UNKNOWN_FACE_TYPE ,   CONVEX = SoShapeHintsElement::CONVEX }
	Hints about faces of shape: if all faces are known to be convex or not. More...
enum	WindingType {   NO_WINDING_TYPE = SoShapeHintsElement::NO_WINDING_TYPE ,   ODD_TYPE = SoShapeHintsElement::ODD_TYPE ,   NON_ZERO_TYPE = SoShapeHintsElement::NON_ZERO_TYPE ,   POSITIVE_TYPE = SoShapeHintsElement::POSITIVE_TYPE ,   NEGATIVE_TYPE = SoShapeHintsElement::NEGATIVE_TYPE ,   ABS_GEQ_TWO_TYPE = SoShapeHintsElement::ABS_GEQ_TWO_TYPE }
	Winding type possible values. More...

Public Member Functions
virtual SoType	getTypeId () const
	Returns the type identifier for this specific instance.
	SoShapeHints ()
	Creates a shape hints node with default settings.
virtual void	setOverride (const SbBool state)
	Set the state of the override field.
virtual SbBool	isOverride () const
	Returns the state of the override field.
Public Member Functions inherited from SoNode
virtual SoNode *	copy (SbBool copyConnections=FALSE) const
	Creates and returns an exact copy of the node.
virtual SbBool	affectsState () const
	Returns TRUE if a node has an effect on the state during traversal.
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 SbBool	isVBOSupported ()
	Indicates if Vertex Buffer Object (VBO) is supported by your graphics board.
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
SoSFEnum	vertexOrdering
	Indicates how the vertices of faces are ordered.
SoSFEnum	shapeType
	Indicates whether the shape is known to enclose a volume (SOLID) or not.
SoSFEnum	faceType
	Indicates whether each face is convex.
SoSFEnum	windingType
	Indicates the winding rule used to define holes in a polygon.
SoSFBool	useVBO
	This field controls whether subsequent shapes in the scene graph can use OpenGL Vertex Buffer Objects (VBO) to speed up rendering.
SoSFFloat	creaseAngle
	Indicates the minimum angle (in radians) between two adjacent face normals required to form a sharp crease at the edge when normal vectors are computed automatically by Open Inventor.
SoSFFloat	neighborTolerance
	Specifies the tolerance value to use when default normals are computed.

Detailed Description

Node that provides hints about shapes.

By default, Open Inventor assumes very little about the shapes it renders. You can use the SoShapeHints node to indicate that vertex-based shapes (those derived from SoVertexShape) are solid, contain ordered vertices, or contain convex faces. For fastest rendering, specify SOLID, COUNTERCLOCKWISE, CONVEX shapes.

These hints allow Open Inventor to optimize certain rendering features. Optimizations that may be performed include enabling back-face culling and disabling two-sided lighting. For example, if an object is solid and has ordered vertices, Open Inventor turns on backface culling and turns off two-sided lighting. If the object is not solid but has ordered vertices, it turns off backface culling and turns on two-sided lighting. In all other cases, both backface culling and two-sided lighting are off.
Summary:

• Two-sided lighting: enabled if not solid and has ordered vertices.
  Set vertexOrdering to COUNTERCLOCKWISE (usually) or CLOCKWISE.
• Backface culling: enabled if solid and has ordered vertices.
  Set shapeType to SOLID.

Note: Two-sided lighting is automatically enabled for VolumeViz "slice" primitives, such as SoOrthoSlice and SoVolumeSkin.

This node allows the creation of polygons with holes. See the windingType field description, SoIndexedFaceSet, and SoFaceSet for details.

The SoShapeHints node also affects how default normals are generated. When a node derived from SoVertexShape has to generate default normals, it uses the creaseAngle field to determine which edges should be smooth-shaded and which ones should have a sharp crease. The crease angle is the angle between surface normals on adjacent polygons. For example, a crease angle of .5 radians means that an edge between two adjacent polygonal faces will be smooth shaded if the normals to the two faces form an angle that is less than .5 radians (about 30 degrees). Otherwise, it will be faceted.

creaseAngle = 0	creaseAngle = 0.5	creaseAngle = PI
br

Smooth shaded means that the normal vectors of all the faces that share a vertex are averaged together to compute the normal vector for that vertex.

Normal averaging

br

Normal generation is fastest when the creaseAngle is 0 (the default), producing one normal per facet. However, if a vertex is shared by two (or more) faces that should be faceted, the result of normal generation will be multiple normal vectors (one for each face) associated with that vertex. This is in conflict with using OpenGL Vertex Buffer Objects (VBO), which usually provide the best performance. VBO rendering only allows per-vertex (not per-face) normal vectors and only one normal vector per vertex. Some high-level shapes, like SoIndexedFaceSet, will automatically reorganize the geometry data to produce the requested appearance and still use VBOs for rendering. Lower level shapes like SoBufferedShape will ignore the creaseAngle field and compute normals using a crease angle of Pi in order to use VBOs for rendering. A creaseAngle of Pi produces one averaged normal per vertex.

See SoVertexShape for more information about Vertex Buffer Objects and shape rendering.

FILE FORMAT/DEFAULT

ShapeHints {

vertexOrdering	UNKNOWN_ORDERING
shapeType	UNKNOWN_SHAPE_TYPE
faceType	CONVEX
windingType	NO_WINDING_TYPE
creaseAngle	0
neighborTolerance	1e-6
useVBO	TRUE

}

ACTION BEHAVIOR

SoGLRenderAction, SoCallbackAction, SoRayPickAction, SoGetBoundingBoxAction
Sets the state to contain the hints; sets up optimizations based on the hints. Sets: SoShapeHintsElement, SoCreaseAngleElement, SoNeighborToleranceElement

SEE ALSO

SoVertexShape SoIndexedFaceSet SoFaceSet

Definition at line 171 of file SoShapeHints.h.

Member Enumeration Documentation

FaceType

enum SoShapeHints::FaceType

Hints about faces of shape: if all faces are known to be convex or not.

Enumerator
UNKNOWN_FACE_TYPE	Nothing is known about faces.
CONVEX	All faces are convex.

Definition at line 212 of file SoShapeHints.h.

ShapeType

enum SoShapeHints::ShapeType

Hints about entire shape: if shape is known to be a solid object, as opposed to a surface.

Enumerator
UNKNOWN_SHAPE_TYPE	Nothing is known about the shape.
SOLID	The shape encloses a volume.

Definition at line 200 of file SoShapeHints.h.

VertexOrdering

enum SoShapeHints::VertexOrdering

Hints about ordering of face vertices: if ordering of all vertices of all faces is known to be consistent when viewed from "outside" shape or not.

Enumerator
UNKNOWN_ORDERING	Ordering of vertices is unknown.
CLOCKWISE	Face vertices are ordered clockwise (from the outside)
COUNTERCLOCKWISE	Face vertices are ordered counterclockwise (from the outside)

Definition at line 181 of file SoShapeHints.h.

WindingType

enum SoShapeHints::WindingType

Winding type possible values.

Enumerator
NO_WINDING_TYPE	Draw without holes (default).
ODD_TYPE	Regions with odd winding numbers are filled. This is the most commonly used winding rule.
NON_ZERO_TYPE	Regions with non-zero winding numbers are filled.
POSITIVE_TYPE	Regions with positive winding numbers are filled.
NEGATIVE_TYPE	Regions with negative winding numbers are filled.
ABS_GEQ_TWO_TYPE	Regions with winding numbers whose absolute value is greater than or equal to two are filled.

Definition at line 224 of file SoShapeHints.h.

Constructor & Destructor Documentation

SoShapeHints()

SoShapeHints::SoShapeHints

(

)

Creates a shape hints node with default settings.

Member Function Documentation

getClassTypeId()

static SoType SoShapeHints::getClassTypeId ( )

static

Returns the type identifier for this class.

getTypeId()

virtual SoType SoShapeHints::getTypeId ( ) const

virtual

Returns the type identifier for this specific instance.

Reimplemented from SoNode.

isOverride()

virtual SbBool SoShapeHints::isOverride ( ) const

inlinevirtual

Returns the state of the override field.

Reimplemented from SoNode.

Definition at line 388 of file SoShapeHints.h.

isVBOSupported()

static SbBool SoShapeHints::isVBOSupported ( )

static

Indicates if Vertex Buffer Object (VBO) is supported by your graphics board.

setOverride()

virtual void SoShapeHints::setOverride ( const SbBool  state )

inlinevirtual

Set the state of the override field.

see SoNode::setOverride doc.

Reimplemented from SoNode.

Definition at line 382 of file SoShapeHints.h.

Member Data Documentation

creaseAngle

SoSFFloat SoShapeHints::creaseAngle

Indicates the minimum angle (in radians) between two adjacent face normals required to form a sharp crease at the edge when normal vectors are computed automatically by Open Inventor.

It has no effect when normal vectors are explicitly provided by the application.

Definition at line 349 of file SoShapeHints.h.

faceType

SoSFEnum SoShapeHints::faceType

Indicates whether each face is convex.

Because the penalty for non-convex faces is very steep (faces must be triangulated expensively), the default assumes all faces are convex. Therefore, shapes with concave faces may not be displayed correctly unless this hint is set to UNKNOWN_FACE_TYPE. Use enum FaceType. Default is CONVEX.

Definition at line 280 of file SoShapeHints.h.

neighborTolerance

SoSFFloat SoShapeHints::neighborTolerance

Specifies the tolerance value to use when default normals are computed.

The default is 1e-6.

Specifically it determines which (other) points in the shape are close enough to influence the normal at each vertex.
Setting a smaller tolerance value will select a smaller number of points and can reduce the time required for computing normals on very large, very dense geometry.

If the OIV_NORMGEN_TOLERANCE environment variable is set, the default is 1/OIV_NORMGEN_TOLERANCE.

NOTE: field available since Open Inventor 8.0

Definition at line 366 of file SoShapeHints.h.

shapeType

SoSFEnum SoShapeHints::shapeType

Indicates whether the shape is known to enclose a volume (SOLID) or not.

If the inside (the side away from the surface normal) of any part of the shape is visible, the shape is not solid. Use enum ShapeType. Default is UNKNOWN_SHAPE_TYPE.

Definition at line 272 of file SoShapeHints.h.

useVBO

SoSFBool SoShapeHints::useVBO

This field controls whether subsequent shapes in the scene graph can use OpenGL Vertex Buffer Objects (VBO) to speed up rendering.

Default is TRUE (since Open Inventor 8.1). The default value can be set using the OIV_FORCE_USE_VBO environment variable (see SoPreferences).

In most cases there is no reason to set this field. Open Inventor will automatically choose the best rendering strategy. For example, VBOs generally provide the best performance for large shapes (many vertices), but not necessarily for small shapes. In specific cases it may be useful to influence these decisions using this field and/or the related environment variables including OIV_MIN_VERTEX_VBO and OIV_MIN_VERTEX_VAVBO_NOCACHE. See SoVertexShape for more discussion about shape rendering strategy.

NOTE: field available since Open Inventor 5.0

Definition at line 341 of file SoShapeHints.h.

vertexOrdering

SoSFEnum SoShapeHints::vertexOrdering

Indicates how the vertices of faces are ordered.

CLOCKWISE ordering means that the vertices of each face form a clockwise loop around the face, when viewed from the outside (the side toward which the normal points). Use enum VertexOrdering. Default is UNKNOWN_ORDERING.

Definition at line 265 of file SoShapeHints.h.

windingType

SoSFEnum SoShapeHints::windingType

Indicates the winding rule used to define holes in a polygon.

It is used by SoIndexedFaceSet and SoFaceSet to determine which parts of the polygon are on the interior and which are on the exterior and should not be filled. By default this field value is NO_WINDING_TYPE, that is, no winding rules are used, so there are no holes. Use enum WindingType.

For a single contour, the winding number of a point is the signed number of revolutions we make around that point while traveling once around the contour (where a counterclockwise revolution is positive and a clockwise revolution is negative). When there are several contours, the individual winding numbers are summed. This procedure associates a signed integer value with each point in the plane. Note that the winding number is the same for all points in a single region.

The following figure shows three sets of contours and winding numbers for points inside those contours. In the left set, all three contours are counterclockwise, so each nested interior region adds one to the winding number. For the middle set, the two interior contours are drawn clockwise, so the winding number decreases and actually becomes negative.

br

The winding rule classifies a region as inside if its winding number belongs to the chosen category (odd, nonzero, positive, negative, or "absolute value of greater than or equal to two"). The odd and nonzero rules are common ways to define the interior. The positive, negative, and "absolute value>=2" winding rules have some limited use for polygon CSG (computational solid geometry) operations. The four sets of contours shown in the following figure are used with different winding rule properties to see their effects. For each winding rule, the dark areas represent interiors. Note the effect of clockwise and counterclockwise winding.

br

NOTE: In LINES drawing style (see SoDrawStyle), if windingType is not NO_WINDING_TYPE, or if faceType is UNKNOWN_FACE_TYPE, the edges of the tessellated triangles will be drawn.

NOTE: field available since Open Inventor 4.0

Definition at line 323 of file SoShapeHints.h.

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

• Inventor/nodes/SoShapeHints.h