Coin: SoNode Class Reference

Coin is a retained mode 3D visualization library (built on top of the immediate mode OpenGL library). "Retained mode" means that instead of passing commands to draw graphics primitives directly to the renderer, you build up data structures which are rendered by the library on demand.

The node classes are the main "primitive" for building these data structures. In Coin, you build tree hierarchies made up of different node types: group nodes (for the tree structure layout of the other nodes), appearance nodes (for setting up materials, textures, etc), shape nodes (for the actual geometry), and nodes for lighting and camera positioning.

One common issue with newcomers to the API is that you should not and can not use the C++ delete operator on nodes -- the destructor is protected. This is because node instances are using a common technique for memory resource handling called "reference counting". Nodes are deleted (actually, they delete themselves) when their unref() method is called and the reference count goes to zero.

One important side-effect of this is that SoNode-derived classes should not be statically allocated, neither in static module memory nor on function's stack-frames. SoNode-derived classes must always be allocated dynamically from the memory heap with the new operator (or else the scheme with self-destruction upon de-referencing to 0 would not work).

Usually application programmers won't manually ref() and unref() nodes a lot, because you pass the nodes directly to SoGroup::addChild() or So*ViewersetSceneGraph() or something similar. These functions will ref() the nodes they are passed, and unref() them when they are finished with them.

Make sure you do ref() nodes that you keep pointers to so they aren't accidentally deleted prematurely due to an unref() call from within the library itself. If you haven't manually called ref() on a top-level root node, it will then be deleted automatically. This code shows how to do it:

  SoSeparator * root = new SoSeparator; // root's refcount starts out at zero
  root->addChild(foo_node); // foo_node refcount is increased by 1
  root->addChild(bar_node); // bar_node refcount +1

  // increase refcount before passing it to setScenegraph(), to avoid
  // premature destruction
  root->ref();

  myviewer->setSceneGraph(root); // root's refcount +1, is now 2

  // [misc visualization and processing]

  // myviewer will let go of it's reference to the root node, thereby
  // decreasing it's referencecount by 1
  myviewer->setSceneGraph(NULL);

  // root's refcount goes from +1 to 0, and it will self-destruct controllably
  root->unref();
  // avoid dangling pointer, in case "root" is attempted used again
  // (not really necessary, but good for smoking out bugs early)
  root = NULL;

For full information and tutorial-style introductions to all API issues, see the "Inventor Mentor: Programming Object-Oriented 3D Graphics with Open Inventor" (ISBN 0-201-62495-8). It has detailed explanations on all the basic principles involved.

See specifically the section "References and Deletion" in Chapter 3 to learn about the reference counting techniques.

Often when using the Coin library, one is interested in making extensions to it. Of particular interest is setting up extension nodes, which are then traversed, rendered and otherwise used by the rest of the library as any internal node.

The Coin header file Inventor/nodes/SoSubNode.h includes a set of convenience macros for quick and easy construction of extension nodes. Here's a complete snippet of code which shows how to set up a skeleton framework for an extension node class:

  #include <Inventor/nodes/SoWWWInline.h>


  class MyWWWInline : public SoWWWInline {
    SO_NODE_HEADER(MyWWWInline);

  public:
    static void initClass(void);
    MyWWWInline(void);

  protected:
    virtual ~MyWWWInline();
  };


  SO_NODE_SOURCE(MyWWWInline);

  MyWWWInline::MyWWWInline(void)
  {
    SO_NODE_CONSTRUCTOR(MyWWWInline);
  }

  MyWWWInline::~MyWWWInline()
  {
  }

  void
  MyWWWInline::initClass(void)
  {
    SO_NODE_INIT_CLASS(MyWWWInline, SoWWWInline, "SoWWWInline");
  }


  int
  main(int argc, char ** argv)
  {
    SoDB::init();
    MyWWWInline::initClass();

    // [...]

    return 0;
  }

You can then override for instance the GLRender() method to have your new class render OpenGL geometry different from it's superclass.

For extending the Coin library with your own classes, we strongly recommend that you make yourself acquainted with the excellent «The Inventor Toolmaker» book (ISBN 0-201-62493-1), which describes the tasks involved in detail. This book was written by the original SGI Inventor designers and explains many of the underlying design ideas, aswell as having lots of hands-on examples on how to extend the Coin toolkit in ways that are true to the fundamental design ideas. («The Inventor Toolmaker» is also available at SGI's online library, at no cost. See Download The Inventor Toolmaker.) Reading the sourcecode of the built-in classes in Coin should also provide very helpful.

For information about dynamic loading of extension nodes, see the documentation of SoType::fromName().

Member Enumeration Documentation

enum SoNode::NodeType

Used to store node type.

Enumerator:

INVENTOR	Specifies Inventor node type.
VRML1	Node is VRML V1.0 compatible.
VRML2	Node is from the VRML V2.0 specification.
INVENTOR_1	Node was part of SGI Inventor version 1.
INVENTOR_2_0	Node was part of SGI Inventor version 2.0.
INVENTOR_2_1	Node was introduced with SGI / TGS Inventor version 2.1.
INVENTOR_2_5	Node was introduced with TGS Inventor version 2.5.
INVENTOR_2_6	Node was introduced with TGS Inventor version 2.6.
COIN_1_0	Node was part of Coin version 1.
COIN_2_0	Node was introduced with Coin 2.0.
EXTENSION	Node is a client code extension.

Constructor & Destructor Documentation

SoNode::SoNode ( void ) [protected]

Default constructor, initializes node instance.

SoNode::~SoNode ( ) [protected, virtual]

Destructor.

Member Function Documentation

void SoNode::setOverride ( const SbBool state )

Set the override flag.

If this flag is TRUE, the field values of this node will override the field values of other nodes of the same type during scene graph traversal.

A common applicaton for "override nodes" is to place them at the top of the tree as a convenient way to force e.g. a common drawstyle on the complete tree.

The override flag does not exist in the Inventor file format. This flag is in other words not persistent, and must be programmatically set. The rationale for this flag is for viewers to be able to control rendering style of the 3D models, so it would look stupid if some parts of certain models suddenly didn't adhere to the viewer mode.

SbBool SoNode::isOverride ( void ) const

Return status of override flag.

See also:: setOverride()

uint32_t SoNode::getCompatibilityTypes ( const SoType & nodetype ) [static]

Get the node compatibility mask for node type nodetype. The return value will be a bit mask of SoNode::NodeType flags, containing one or several flags.

This function is an extension for Coin, and it is not available in the original SGI Open Inventor v2.1 API.

Since:: Coin 2.0

void SoNode::setNodeType ( const NodeType type )

Sets the node type for this node to type. Since some nodes should be handled differently in VRML1 vs. Inventor, this should be used to get correct behavior for those cases. The default node type is INVENTOR.

This method is an extension versus the Open Inventor API.

See also:: getNodeType()

SoNode::NodeType SoNode::getNodeType ( void ) const

Returns the node type set for this node.

This method is an extension versus the Open Inventor API.

See also:: setNodeType()

SoNode * SoNode::copy ( SbBool copyconnections = 0 ) const [virtual]

Make a duplicate of this node and return a pointer to the duplicate.

If this node is a group node, children are also copied and we return a pointer to the root of a full copy of the subgraph rooted here.

If copyconnections is TRUE, we also copy the connections to fields within this node (and ditto for any children and children's children etc).

Note that this function has been made virtual in Coin, which is not the case in the original Open Inventor API. We may change this method back into being non-virtual again for major Coin versions after this, as it was made virtual more or less by mistake. So please don't write application code that depends on SoNode::copy() being virtual.

The reason this method should not be virtual is because this is not the function the application programmer should override in extension nodes if she needs some special behavior during a copy operation (like copying the value of internal data not exposed as fields).

For that purpose, override the copyContents() method. Your overridden copyContents() method should then both copy internal data aswell as calling the parent superclass' copyContents() method for automatically handling of fields and other common data.

SbBool SoNode::affectsState ( void ) const [virtual]

Returns TRUE if the node could have any effect on the state during traversal.

If it returns FALSE, no data in the traversal-state will change from the pre-traversal state to the post-traversal state. The SoSeparator node will for instance return FALSE, as it pushes and pops the state before and after traversal of its children. All SoShape nodes will also return FALSE, as just pushing out geometry data to the rendering engine won't affect the actual rendering state.

The default method returns TRUE, on a "better safe than sorry" philosophy.

Reimplemented in SoNodeKitListPart, SoSceneKit, SoArray, SoMultipleCopy, SoSeparator, SoShape, SoSwitch, SoVRMLLOD, SoVRMLParent, SoVRMLProximitySensor, SoVRMLShape, SoVRMLSwitch, and SoVRMLTouchSensor.

void SoNode::doAction ( SoAction * action ) [virtual]

This function performs the typical operation of a node for any action.

void SoNode::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.

void SoNode::GLRenderBelowPath ( SoGLRenderAction * action ) [virtual]

Implements the SoAction::BELOW_PATH traversal method for the rendering action.

Reimplemented in SoAnnotation, SoExtSelection, SoLOD, SoLocateHighlight, SoSeparator, SoVRMLBillboard, SoVRMLGroup, SoVRMLLOD, SoVRMLTransform, SoShadowGroup, and SoGeoSeparator.

void SoNode::GLRenderInPath ( SoGLRenderAction * action ) [virtual]

Implements the SoAction::IN_PATH traversal method for the rendering action.

Reimplemented in SoAnnotation, SoLOD, SoLocateHighlight, SoSeparator, SoVRMLBillboard, SoVRMLGroup, SoVRMLLOD, SoVRMLTransform, SoShadowGroup, and SoGeoSeparator.

void SoNode::GLRenderOffPath ( SoGLRenderAction * action ) [virtual]

Implements the SoAction::OFF_PATH traversal method for the rendering action.

Reimplemented in SoAnnotation, SoLOD, SoSeparator, SoVRMLBillboard, SoVRMLGroup, and SoVRMLLOD.

void SoNode::callback ( SoCallbackAction * action ) [virtual]

Action method for SoCallbackAction.

Simply updates the state according to how the node behaves for the render action, so the application programmer can use the SoCallbackAction for extracting information about the scene graph.

void SoNode::getBoundingBox ( SoGetBoundingBoxAction * action ) [virtual]

Action method for the SoGetBoundingBoxAction.

Calculates bounding box and center coordinates for node and modifies the values of the action to encompass the bounding box for this node and to shift the center point for the scene more towards the one for this node.

Nodes influencing how geometry nodes calculates their bounding box also overrides this method to change the relevant state variables.

Reimplemented in SoCenterballDragger, SoDragger, SoClipPlaneManip, SoDirectionalLightManip, SoPointLightManip, SoSpotLightManip, SoTransformManip, SoBaseKit, SoNodeKitListPart, SoAntiSquish, SoArray, SoBlinker, SoCallback, SoCamera, SoComplexity, SoCoordinate3, SoCoordinate4, SoFile, SoFont, SoFontStyle, SoGroup, SoIndexedLineSet, SoIndexedNurbsCurve, SoLOD, SoLevelOfDetail, SoLineSet, SoMatrixTransform, SoMultipleCopy, SoNurbsCurve, SoPathSwitch, SoPointSet, SoProfile, SoProfileCoordinate2, SoProfileCoordinate3, SoResetTransform, SoRotation, SoRotationXYZ, SoScale, SoSeparator, SoShape, SoShapeHints, SoSurroundScale, SoSwitch, SoTransform, SoTransformSeparator, SoTranslation, SoUnits, SoVertexProperty, SoWWWInline, SoVRMLBillboard, SoVRMLCoordinate, SoVRMLFontStyle, SoVRMLGroup, SoVRMLIndexedLineSet, SoVRMLInline, SoVRMLLOD, SoVRMLPointSet, SoVRMLProximitySensor, SoVRMLScript, SoVRMLShape, SoVRMLSwitch, SoVRMLTransform, SoVRMLVertexLine, SoVRMLVertexPoint, SoVRMLVertexShape, SoProfilerStats, SoGeoOrigin, SoGeoSeparator, SoGeoLocation, and SoGeoCoordinate.

void SoNode::getMatrix ( SoGetMatrixAction * action ) [virtual]

Action method for SoGetMatrixAction.

Updates action by accumulating with the transformation matrix of this node (if any).

Reimplemented in SoCenterballDragger, SoDragger, SoClipPlaneManip, SoDirectionalLightManip, SoPointLightManip, SoSpotLightManip, SoTransformManip, SoBaseKit, SoNodeKitListPart, SoAntiSquish, SoArray, SoBumpMapTransform, SoCallback, SoFile, SoGroup, SoMatrixTransform, SoMultipleCopy, SoPathSwitch, SoResetTransform, SoRotation, SoRotationXYZ, SoScale, SoSeparator, SoSurroundScale, SoSwitch, SoTexture2Transform, SoTexture3Transform, SoTransform, SoTransformSeparator, SoTranslation, SoUnits, SoWWWInline, SoVRMLBillboard, SoVRMLGroup, SoVRMLInline, SoVRMLSwitch, SoVRMLTextureTransform, SoVRMLTransform, SoProfilerStats, SoGeoOrigin, SoGeoSeparator, and SoGeoLocation.

void SoNode::handleEvent ( SoHandleEventAction * action ) [virtual]

Action method for SoHandleEventAction.

Inspects the event data from action, and processes it if it is something which this node should react to.

Nodes influencing relevant state variables for how event handling is done also overrides this method.

Reimplemented in SoDragger, SoClipPlaneManip, SoDirectionalLightManip, SoPointLightManip, SoSpotLightManip, SoTransformManip, SoBaseKit, SoNodeKitListPart, SoArray, SoCallback, SoCamera, SoEventCallback, SoExtSelection, SoFile, SoGroup, SoLocateHighlight, SoMultipleCopy, SoPathSwitch, SoSelection, SoSeparator, SoSwitch, SoWWWAnchor, SoWWWInline, SoVRMLAnchor, SoVRMLDragSensor, SoVRMLInline, SoVRMLScript, SoVRMLSwitch, SoVRMLTimeSensor, SoVRMLTouchSensor, and SoProfilerStats.

void SoNode::pick ( SoPickAction * action ) [virtual]

Action method for SoPickAction.

Does common processing for SoPickAction action instances.

void SoNode::rayPick ( SoRayPickAction * action ) [virtual]

Action method for SoRayPickAction.

Checks the ray specification of the action and tests for intersection with the data of the node.

Nodes influencing relevant state variables for how picking is done also overrides this method.

Reimplemented in SoDragger, SoBaseKit, SoBumpMap, SoCamera, SoCone, SoCube, SoCylinder, SoImage, SoIndexedNurbsCurve, SoIndexedNurbsSurface,


Public Types
	INVENTOR = 0x0000
	VRML1 = 0x0001
	VRML2 = 0x0002
	INVENTOR_1 = 0x0004
	INVENTOR_2_0 = 0x0008
	INVENTOR_2_1 = 0x0010
	INVENTOR_2_5 = 0x0020
	INVENTOR_2_6 = 0x0040
	COIN_1_0 = 0x0080
	COIN_2_0 = 0x0100
	EXTENSION = 0x0200
	COIN_2_2 = 0x0400
	COIN_2_3 = 0x0800
	COIN_2_4 = 0x1000
	INVENTOR_5_0 = 0x2000
	COIN_2_5 = 0x4000
	COIN_3_0 = 0x8000
enum	NodeType { INVENTOR = 0x0000, VRML1 = 0x0001, VRML2 = 0x0002, INVENTOR_1 = 0x0004, INVENTOR_2_0 = 0x0008, INVENTOR_2_1 = 0x0010, INVENTOR_2_5 = 0x0020, INVENTOR_2_6 = 0x0040, COIN_1_0 = 0x0080, COIN_2_0 = 0x0100, EXTENSION = 0x0200, COIN_2_2 = 0x0400, COIN_2_3 = 0x0800, COIN_2_4 = 0x1000, INVENTOR_5_0 = 0x2000, COIN_2_5 = 0x4000, COIN_3_0 = 0x8000 }
Public Member Functions
void	setOverride (const SbBool state)
SbBool	isOverride (void) const
void	setNodeType (const NodeType type)
NodeType	getNodeType (void) const
virtual SoNode *	copy (SbBool copyconnections=0) const
virtual SbBool	affectsState (void) const
virtual void	doAction (SoAction *action)
virtual void	GLRender (SoGLRenderAction *action)
virtual void	GLRenderBelowPath (SoGLRenderAction *action)
virtual void	GLRenderInPath (SoGLRenderAction *action)
virtual void	GLRenderOffPath (SoGLRenderAction *action)
virtual void	callback (SoCallbackAction *action)
virtual void	getBoundingBox (SoGetBoundingBoxAction *action)
virtual void	getMatrix (SoGetMatrixAction *action)
virtual void	handleEvent (SoHandleEventAction *action)
virtual void	pick (SoPickAction *action)
virtual void	rayPick (SoRayPickAction *action)
virtual void	search (SoSearchAction *action)
virtual void	write (SoWriteAction *action)
virtual void	audioRender (SoAudioRenderAction *action)
virtual void	getPrimitiveCount (SoGetPrimitiveCountAction *action)
virtual void	grabEventsSetup (void)
virtual void	grabEventsCleanup (void)
virtual void	startNotify (void)
virtual void	notify (SoNotList *l)
uint32_t	getNodeId (void) const
virtual SoChildList *	getChildren (void) const
virtual void	writeInstance (SoOutput *out)
virtual SoNode *	addToCopyDict (void) const
virtual void	copyContents (const SoFieldContainer *from, SbBool copyconnections)
virtual SoFieldContainer *	copyThroughConnection (void) const
Static Public Member Functions
static uint32_t	getCompatibilityTypes (const SoType &nodetype)
static SoType	getClassTypeId (void)
static SoNode *	getByName (const SbName &name)
static int	getByName (const SbName &name, SoNodeList &l)
static void	initClass (void)
static void	initClasses (void)
static uint32_t	getNextNodeId (void)
static int	getActionMethodIndex (const SoType type)
static void	getBoundingBoxS (SoAction action, SoNode node)
static void	GLRenderS (SoAction action, SoNode node)
static void	callbackS (SoAction action, SoNode node)
static void	getMatrixS (SoAction action, SoNode node)
static void	handleEventS (SoAction action, SoNode node)
static void	pickS (SoAction action, SoNode node)
static void	rayPickS (SoAction action, SoNode node)
static void	searchS (SoAction action, SoNode node)
static void	writeS (SoAction action, SoNode node)
static void	audioRenderS (SoAction action, SoNode node)
static void	getPrimitiveCountS (SoAction action, SoNode node)
Protected Member Functions
	SoNode (void)
virtual	~SoNode ()
virtual SbBool	readInstance (SoInput *in, unsigned short flags)
Static Protected Member Functions
static const SoFieldData **	getFieldDataPtr (void)
static void	setNextActionMethodIndex (int index)
static int	getNextActionMethodIndex (void)
static void	incNextActionMethodIndex (void)
static void	setCompatibilityTypes (const SoType &nodetype, const uint32_t bitmask)
Protected Attributes
uint32_t	uniqueId
Static Protected Attributes
static uint32_t	nextUniqueId = 1
static int	nextActionMethodIndex = 0

SoNode Class Reference
[Node Classes]

Detailed Description

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Static Protected Member Functions

Protected Attributes

Static Protected Attributes

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

SoNode Class Reference [Node Classes]

Detailed Description

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Static Protected Member Functions

Protected Attributes

Static Protected Attributes

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

SoNode Class Reference
[Node Classes]