Element Classes

The element classes in Coin are the containers of state information during action traversals of scene graphs. More...

## Classes

class | SoGLCacheContextElement
| The SoGLCacheContextElement class handles the OpenGL cache for a context. More...
class | SoGLClipPlaneElement
| The SoGLClipPlaneElement class is yet to be documented. More...
class | SoGLColorIndexElement
| The SoGLColorIndexElement class sets the current OpenGL color. More...
class | SoGLCoordinateElement
| The SoGLCoordinateElement class is yet to be documented. More...
class | SoGLDepthBufferElement
| The SoGLDepthBufferElement controls the OpenGL depth buffer. More...
class | SoGLDrawStyleElement
| The SoGLDrawStyleElement updates the current draw style in OpenGL. More...
class | SoGLEnvironmentElement
| The SoGLEnvironmentElement class is for setting GL fog etc. More...
class | SoGLLazyElement
| The SoGLLazyElement class is meant to optimize GL rendering. More...
class | SoGLLightIdElement
| The SoGLLightIdElement class is yet to be documented. More...
class | SoGLLinePatternElement
| The SoGLLinePatternElement class changes the line stipple pattern of the OpenGL render state. More...
class | SoGLLineWidthElement
| The SoGLLineWidthElement class changes the line width setting of the OpenGL render state. More...
class | SoGLModelMatrixElement
| The SoGLModelMatrixElement class is yet to be documented. More...
class | SoGLMultiTextureCoordinateElement
| The SoGLMultiTextureCoordinateElement class stores the current gltexture coordinates for several units. More...
class | SoGLMultiTextureEnabledElement
| The SoGLMultiTextureEnabledElement class is an element which controls whether texturing is enabled or not. More...
class | SoGLMultiTextureMatrixElement
| The SoGLMultiTextureMatrixElement class is used to update the OpenGL texture matrix. More...
class | SoGLMultiTextureImageElement
| The SoGLMultiTextureImageElement class is used to control the current GL texture for texture units. More...
class | SoGLNormalElement
| The SoGLNormalElement class is yet to be documented. More...
class | SoGLPointSizeElement
| The SoGLPointSizeElement class changes the point size setting of the OpenGL render state. More...
class | SoGLPolygonOffsetElement
| The SoGLPolygonOffsetElement class is yet to be documented. More...
class | SoGLProjectionMatrixElement
| The SoGLProjectionMatrixElement class is yet to be documented. More...
class | SoGLRenderPassElement
| The SoGLRenderPassElement class is yet to be documented. More...
class | SoGLShapeHintsElement
| The SoGLShapeHintsElement class is yet to be documented. More...
class | SoGLUpdateAreaElement
| The SoGLUpdateAreaElement class is yet to be documented. More...
class | SoGLVBOElement
| The SoGLVBOElement class is used to store VBO state. More...
class | SoGLViewingMatrixElement
| The SoGLViewingMatrixElement class is used to store the current viewing matrix. More...
class | SoGLViewportRegionElement
| The SoGLViewportRegionElement class is yet to be documented. More...
class | SoGLDisplayList
| The SoGLDisplayList class stores and manages OpenGL display lists. More...
class | SoGLVertexAttributeElement
| The SoGLVertexAttributeElement class is yet to be documented. More...
class | SoAccumulatedElement
| The SoAccumulatedElement class is an abstract class for storing accumulated state. More...
class | SoAmbientColorElement
| The SoAmbientColorElement class is yet to be documented. More...
class | SoAnnoText3CharOrientElement
| The SoAnnoText3CharOrientElement class is yet to be documented. More...
class | SoAnnoText3FontSizeHintElement
| The SoAnnoText3FontSizeHintElement class is yet to be documented. More...
class | SoAnnoText3RenderPrintElement
| The SoAnnoText3RenderPrintElement class is yet to be documented. More...
class | SoBBoxModelMatrixElement
| The SoBBoxModelMatrixElement class keeps track of the current model matrix during a scene graph traversal. It is used by amongst others the SoGetBoundingBoxAction class. More...
class | SoBumpMapElement
| The SoBumpMapElement class is yet to be documented. More...
class | SoBumpMapCoordinateElement
| The SoBumpMapCoordinateElement class is yet to be documented. More...
class | SoBumpMapMatrixElement
| The SoBumpMapMatrixElement class is used to manage the bump map matrix stack. More...
class | SoCacheElement
| The SoCacheElement class stores and manages the open caches. More...
class | SoCacheHintElement
| The SoCacheHintElement class is yet to be documented. More...
class | SoClipPlaneElement
| The SoClipPlaneElement class is used to manage the clip plane stack. More...
class | SoComplexityElement
| The SoComplexityElement class contains the current shape complexity for a graph traverser. More...
class | SoComplexityTypeElement
| The SoComplexityTypeElement class is yet to be documented. More...
class | SoCoordinateElement
| The SoCoordinateElement class is yet to be documented. More...
class | SoCreaseAngleElement
| The SoCreaseAngleElement class stores the crease angle during a scene graph traversal. More...
class | SoCullElement
| The SoCullElement class is used internally for render and pick culling. More...
class | SoDecimationPercentageElement
| The SoDecimationPercentageElement class is yet to be documented. More...
class | SoDecimationTypeElement
| The SoDecimationTypeElement class is yet to be documented. More...
class | SoDepthBufferElement
| The SoDepthBufferElement controls the depth buffer settings. More...
class | SoDiffuseColorElement
| The SoDiffuseColorElement class is yet to be documented. More...
class | SoDrawStyleElement
| The SoDrawStyleElement class is yet to be documented. More...
class | SoElement
| SoElement is the abstract base class for all elements. More...
class | SoEmissiveColorElement
| The SoEmissiveColorElement class is yet to be documented. More...
class | SoEnvironmentElement
| The SoEnvironmentElement class is yet to be documented. More...
class | SoFloatElement
| SoFloatElement is an abstract base class for elements that consists of a single float value. More...
class | SoFocalDistanceElement
| The SoFocalDistanceElement class is yet to be documented. More...
class | SoFontNameElement
| The SoFontNameElement class is yet to be documented. More...
class | SoFontSizeElement
| The SoFontSizeElement class is yet to be documented. More...
class | SoInt32Element
| The SoInt32Element class is the base class for elements that simply store a 32-bit integer. More...
class | SoLazyElement
| The SoLazyElement class is used to handle material and shape properties. More...
class | SoLightAttenuationElement
| The SoLightAttenuationElement class is yet to be documented. More...
class | SoLightElement
| The SoLightElement class manages the currently active light sources. More...
class | SoLightModelElement
| The SoLightModelElement class is yet to be documented. More...
class | SoLinePatternElement
| The SoLinePatternElement class defines the line stipple pattern. More...
class | SoLineWidthElement
| The SoLineWidthElement class changes the line width setting of the render state. More...
class | SoLocalBBoxMatrixElement
| The SoLocalBBoxMatrixElement class is yet to be documented. More...
class | SoMaterialBindingElement
| The SoMaterialBindingElement class is yet to be documented. More...
class | SoVertexAttributeBindingElement
| The SoVertexAttributeBindingElement class is yet to be documented. More...
class | SoMultiTextureCoordinateElement
| The SoMultiTextureCoordinateElement class is yet to be documented. More...
class | SoMultiTextureEnabledElement
| The SoMultiTextureEnabledElement class is an element which stores whether texturing is enabled or not. More...
class | SoMultiTextureMatrixElement
| The SoMultiTextureMatrixElement class is used to manage the texture matrix stack for texture units > 0. More...
class | SoMultiTextureImageElement
| The SoMultiTextureImageElement class is yet to be documented. More...
class | SoModelMatrixElement
| The SoModelMatrixElement class is used to manage the current transformation. More...
class | SoNormalBindingElement
| The SoNormalBindingElement is yet to be documented. More...
class | SoNormalElement
| The SoNormalElement class is yet to be documented. More...
class | SoOverrideElement
| The SoOverrideElement maintains a list of overridable elements and a list over which elements should be overridden. More...
class | SoPickRayElement
| The SoPickRayElement class is yet to be documented. More...
class | SoPickStyleElement
| The SoPickStyleElement is yet to be documented. More...
class | SoPointSizeElement
| The SoPointSizeElement changes the point size setting of the render state. More...
class | SoPolygonOffsetElement
| The SoPolygonOffsetElement class is yet to be documented. More...
class | SoProfileCoordinateElement
| The SoProfileCoordinateElement class is yet to be documented. More...
class | SoProfileElement
| The SoProfileElement class is yet to be documented. More...
class | SoProjectionMatrixElement
| The SoProjectionMatrixElement class is yet to be documented. More...
class | SoReplacedElement
| The SoReplacedElement class is an abstract element superclass. More...
class | SoShapeHintsElement
| The SoShapeHintsElement class is yet to be documented. More...
class | SoShapeStyleElement
| The SoShapeStyleElement class is yet to be documented. More...
class | SoShininessElement
| The SoShininessElement class is yet to be documented. More...
class | SoSpecularColorElement
| The SoSpecularColorElement is yet to be documented. More...
class | SoSwitchElement
| The SoSwitchElement class is yet to be documented. More...
class | SoTextOutlineEnabledElement
| The SoTextOutlineEnabledElement class is yet to be documented. More...
class | SoTextureCombineElement
| The SoTextureCombineElement class is yet to be documented. More...
class | SoTextureCoordinateBindingElement
| The SoTextureCoordinateBindingElement class is yet to be documented. More...
class | SoTextureOverrideElement
| The SoTextureOverrideElement makes it possible to override texture elements. More...
class | SoTextureUnitElement
| The SoTextureUnitElement class is yet to be documented. More...
class | SoTextureQualityElement
| The SoTextureQualityElement is yet to be documented. More...
class | SoTransparencyElement
| The SoTransparencyElement is yet to be documented. More...
class | SoUnitsElement
| The SoUnitsElement class is yet to be documented. More...
class | SoViewVolumeElement
| The SoViewVolumeElement class is yet to be documented. More...
class | SoViewingMatrixElement
| The SoViewingMatrixElement class stores the world-to-camera transformation. More...
class | SoViewportRegionElement
| The SoViewportRegionElement class is yet to be documented. More...
class | SoWindowElement
| The SoWindowElement class is used to store current window attributes. More...
class | SoListenerPositionElement
| The SoListenerPositionElement holds the position of the current listener. More...
class | SoListenerOrientationElement
| The SoListenerOrientationElement holds the orientation of the current listener. More...
class | SoListenerGainElement
| The SoListenerGainElement class stores the SoListener gain during a scene graph traversal. More...
class | SoListenerDopplerElement
| The SoListenerDopplerElement holds the Doppler velocity and factor of the current listener. More...
class | SoSoundElement
| The SoSoundElement is used for optimizing audio rendering and for turning off inactive SoVRMLSound nodes. More...
class | SoVertexAttributeElement
| The SoVertexAttributeElement class is yet to be documented. More...
class | SoShadowStyleElement
| The SoShadowStyleElement class is yet to be documented. More...
class | SoGLShadowCullingElement
| The SoGLShadowCullingElement class is yet to be documented. More...
class | SoGeoElement
| The SoGeoElement class is yet to be documented. More...
class | SoProfilerTopEngine
| The SoProfilerTopEngine class is yet to be documented. More...
class | SoNodeVisualize
| The SoNodeVisualize class is yet to be documented. More...

## Detailed Description

The element classes in Coin are the containers of state information during action traversals of scene graphs.

One element usually corresponds to one item of information, or sometimes a group of related information values. The elements work like a stack that is pushed and popped as the action traverses in and out of SoSeparator nodes, and the action will always just inspect the top of the stack when it needs to know a value.

Elements are internal implementation details of the workings of nodes and actions, and is not something one needs to worry about before writing ones own extension nodes. Writing extension elements is even more removed from plain Open Inventor usage, but is fully possible for the experienced Open Inventor developer.

### The Element Classes

Elements are mostly internal to Coin, unless you create new extension nodes over Coin. Then you will probably need to know about them.
Elements are part of the design for scene graph traversal in Coin.
It works like this: any traversal action instantiates and keeps a single SoState instance during traversal. The SoState instance uses SoElement objects as "memory units" to keep track of the current state for any feature of the scene graph nodes.
As an example, consider the SoPointSize node: when the SoPointSize node is traversed by for instance a SoGLRenderAction, it will itself push a SoPointSizeElement onto the SoGLRenderAction's SoState stack. Later, when a SoPointSet node occurs in the scene graph, it will request the current point size value from the SoState by reading off the value of its SoPointSizeElement.
SoSeparator nodes will push and pop elements on and off the state stack, so anything that changes state below a SoSeparator node will not influence anything above the SoSeparator.

For more information on the theoretical underpinnings of this traversal design, you should consider reading available literature on the so-called "Visitor pattern". We recommend "Design Patterns", by Gamma, Helm, Johnson, Vlissides (aka the "Gang Of Four"). This book actually uses the Inventor API traversal mechanism as the case study for explaining the Visitor pattern.
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, as well 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 source code of the built-in classes in Coin should also prove very helpful.
The following is a complete example on how to extend Coin with your own traversal elements. First, the class declaration of the new element (i.e. the header include file):

// [texturefilenameelement.h]
#ifndef TEXTUREFILENAMEELEMENT_H
#define TEXTUREFILENAMEELEMENT_H
#include <Inventor/elements/SoReplacedElement.h>
#include <Inventor/SbString.h>
class TextureFilenameElement : public SoReplacedElement {
typedef SoReplacedElement inherited;
SO_ELEMENT_HEADER(TextureFilenameElement);
public:
static void initClass(void);
virtual void init(SoState * state);
static void set(SoState * const state, SoNode * const node,
const SbString & filename);
static const SbString & get(SoState * const state);
static const TextureFilenameElement * getInstance(SoState * state);
protected:
virtual ~TextureFilenameElement();
virtual void setElt(const SbString & filename);
private:
SbString filename;
};
#endif // !TEXTUREFILENAMEELEMENT_H
SbString
The SbString class is a string class with convenience functions for string operations.
Definition SbString.h:52
SoNode
The SoNode class is the base class for nodes used in scene graphs.
Definition SoNode.h:56
SoReplacedElement
The SoReplacedElement class is an abstract element superclass.
Definition SoReplacedElement.h:39
SoReplacedElement::initClass
static void initClass(void)
Definition SoReplacedElement.cpp:77
SoReplacedElement::init
virtual void init(SoState *state)
Definition SoReplacedElement.cpp:91
SoState
The SoState class manages the Coin scene graph traversal state data.
Definition SoState.h:44

The implementation of the element:

// [texturefilenameelement.cpp]
//
// The purpose of the code in this file is to demonstrate how you can
// make your own elements for scene graph traversals.
//
// Code by Peder Blekken <pederb@sim.no>. Copyright (C)
// Kongsberg Oil & Gas Technologies.
#include "texturefilenameelement.h"
SO_ELEMENT_SOURCE(TextureFilenameElement);
void
TextureFilenameElement::initClass(void)
{
SO_ELEMENT_INIT_CLASS(TextureFilenameElement, inherited);
}
void
TextureFilenameElement::init(SoState * state)
{
this->filename = "<none>";
}
TextureFilenameElement::~TextureFilenameElement()
{
}
void
TextureFilenameElement::set(SoState * const state, SoNode * const node,
const SbString & filename)
{
TextureFilenameElement * elem = (TextureFilenameElement *)
SoReplacedElement::getElement(state, classStackIndex, node);
elem->setElt(filename);
}
const SbString &
TextureFilenameElement::get(SoState * const state)
{
return TextureFilenameElement::getInstance(state)->filename;
}
void
TextureFilenameElement::setElt(const SbString & filename)
{
this->filename = filename;
}
const TextureFilenameElement *
TextureFilenameElement::getInstance(SoState * state)
{
return (const TextureFilenameElement *)
SoElement::getConstElement(state, classStackIndex);
}
SoElement::getConstElement
static const SoElement * getConstElement(SoState *const state, const int stackIndex)
Definition SoElement.h:123
SoReplacedElement::getElement
static SoElement * getElement(SoState *const state, const int stackIndex, SoNode *const node)
Definition SoReplacedElement.cpp:142

And a small, standalone test application putting the new element to use:

// [lstextures.cpp]
//
// The purpose of this file is to make a small wrapper "tool" around
// the TextureFilenameElement extension element, just for showing
// example code on how to make use of a user-defined custom element.
//
// The code goes like this:
//
// We initialize the element, enable it for the SoCallbackAction, read
// a scene graph file, set callbacks on SoTexture2 and all shape nodes
// and applies the SoCallbackAction. The callbacks will then print out
// the texture filename information from the TextureFilenameElement
// each time an interesting node is hit.
//
//
// Code by Peder Blekken <pederb@sim.no>. Cleaned up, integrated in
// Coin distribution and commented by Morten Eriksen
// <mortene@sim.no>. Copyright (C) Kongsberg Oil & Gas Technologies.
#include <Inventor/SoDB.h>
#include <Inventor/SoInput.h>
#include <Inventor/actions/SoCallbackAction.h>
#include <Inventor/nodes/SoSeparator.h>
#include <Inventor/nodes/SoTexture2.h>
#include <Inventor/nodes/SoShape.h>
#include <Inventor/misc/SoState.h>
#include <cstdio>
#include "texturefilenameelement.h"
SoCallbackAction::Response
pre_tex2_cb(void * data, SoCallbackAction * action, const SoNode * node)
{
const SbString & filename = ((SoTexture2 *)node)->filename.getValue();
TextureFilenameElement::set(action->getState(), (SoNode *)node, filename);
(void)fprintf(stdout, "=> New texture: %s\n",
filename.getLength() == 0 ?
"<inlined>" : filename.getString());
return SoCallbackAction::CONTINUE;
}
SoCallbackAction::Response
pre_shape_cb(void * data, SoCallbackAction * action, const SoNode * node)
{
const SbString & filename =
TextureFilenameElement::get(action->getState());
(void)fprintf(stdout, " Texturemap on %s: %s\n",
node->getTypeId().getName().getString(),
filename.getLength() == 0 ?
"<inlined>" : filename.getString());
return SoCallbackAction::CONTINUE;
}
void
usage(const char * appname)
{
(void)fprintf(stderr, "\n\tUsage: %s <modelfile.iv>\n\n", appname);
(void)fprintf(stderr,
"\tLists all texture filenames in the model file,\n"
"\tand on which shape nodes they are used.\n\n"
"\tThe purpose of this example utility is simply to\n"
"\tshow how to create and use an extension element for\n"
"\tscene graph traversal.\n\n");
}
int
main(int argc, char ** argv)
{
if (argc != 2) {
usage(argv[0]);
exit(1);
}
SoDB::init();
TextureFilenameElement::initClass();
SO_ENABLE(SoCallbackAction, TextureFilenameElement);
SoInput input;
if (!input.openFile(argv[1])) {
(void)fprintf(stderr, "ERROR: couldn't open file \"%s\".\n", argv[1]);
exit(1);
}
SoSeparator * root = SoDB::readAll(&input);
if (root) {
root->ref();
SoCallbackAction cbaction;
cbaction.addPreCallback(SoTexture2::getClassTypeId(), pre_tex2_cb, NULL);
cbaction.addPreCallback(SoShape::getClassTypeId(), pre_shape_cb, NULL);
cbaction.apply(root);
root->unref();
return 0;
}
return 1;
}
SbName::getString
const char * getString(void) const
Definition SbName.cpp:144
SbString::getLength
int getLength(void) const
Definition SbString.h:76
SbString::getString
const char * getString(void) const
Definition SbString.h:84
SoAction::getState
SoState * getState(void) const
Definition SoAction.cpp:1084
SoAction::apply
virtual void apply(SoNode *root)
Definition SoAction.cpp:463
SoBase::unref
void unref(void) const
Definition SoBase.cpp:530
SoBase::getTypeId
virtual SoType getTypeId(void) const =0
Returns the type identification of an object derived from a class inheriting SoBase....
SoBase::ref
void ref(void) const
Definition SoBase.cpp:478
SoCallbackAction
The SoCallbackAction class invokes callbacks at specific nodes.
Definition SoCallbackAction.h:80
SoCallbackAction::Response
Response
Definition SoCallbackAction.h:94
SoCallbackAction::CONTINUE
@ CONTINUE
Definition SoCallbackAction.h:94
SoCallbackAction::addPreCallback
void addPreCallback(const SoType type, SoCallbackActionCB *cb, void *userdata)
Definition SoCallbackAction.cpp:524
SoDB::readAll
static SoSeparator * readAll(SoInput *input)
Definition SoDB.cpp:682
SoDB::init
static void init(void)
Definition SoDB.cpp:200
SoInput
The SoInput class is an abstraction of file import functionality.
Definition SoInput.h:61
SoInput::openFile
virtual SbBool openFile(const char *fileName, SbBool okIfNotFound=FALSE)
Definition SoInput.cpp:495
SoSeparator
The SoSeparator class is a state-preserving group node.
Definition SoSeparator.h:44
SoShape::getClassTypeId
static SoType getClassTypeId(void)
Definition SoShape.cpp:343
SoTexture2
The SoTexture2 class is used to map a 2D texture onto subsequent geometry in the scene graph.
Definition SoTexture2.h:49
SoTexture2::getClassTypeId
static SoType getClassTypeId(void)
Definition SoTexture2.cpp:407
SoType::getName
SbName getName(void) const
Definition SoType.cpp:675