NAME

       Element Classes -

   Classes
       class SoGLClipPlaneElement
           The SoGLClipPlaneElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLColorIndexElement
       The SoGLColorIndexElement class sets the current OpenGL color.

       This element is only used when the OpenGL canvas is in colorindex mode, ie where colors
       for individual pixels are fetched from a color lookup table ('CLUT'). The usual thing to
       do is to set up a canvas in RGBA truecolor mode. "
   class SoGLCoordinateElement
       The SoGLCoordinateElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLDepthBufferElement
       The SoGLDepthBufferElement controls the OpenGL depth buffer.
   class SoGLDisplayList
       The SoGLDisplayList class stores and manages OpenGL display lists.

       The TEXTURE_OBJECT type is not directly supported in Coin. We handle textures differently
       in a more flexible class called SoGLImage, which also stores some information about the
       texture used when rendering. Old code which use this element should not stop working
       though. The texture object extension will just not be used, and the texture will be stored
       in a display list instead. "
   class SoGLDrawStyleElement
       The SoGLDrawStyleElement updates the current draw style in OpenGL.
   class SoGLEnvironmentElement
       The SoGLEnvironmentElement class is for setting GL fog etc.
   class SoGLLazyElement
       The SoGLLazyElement class is meant to optimize GL rendering.

       This is just a wrap-around implementation for compatibility. It should (hopefully) work in
       the same way as the Inventor class though. "
   class SoGLLightIdElement
       The SoGLLightIdElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLLinePatternElement
       The SoGLLinePatternElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLLineWidthElement
       The SoGLLineWidthElement class changes the linewidth setting of the OpenGL render state.

       Requests from the scenegraph to change the linewidth when rendering OpenGL line primitives
       will be made through this element, which forwards it to the appropriate native OpenGL
       call. "
   class SoGLModelMatrixElement
       The SoGLModelMatrixElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLMultiTextureCoordinateElement
       The SoGLMultiTextureCoordinateElement class stores the current gltexture coordinates for
       several units.
   class SoGLMultiTextureImageElement
       The SoGLMultiTextureImageElement is used to control the current GL texture for texture
       units.
   class SoGLMultiTextureMatrixElement
       The SoGLMultiTextureMatrixElement class is used to update the OpenGL texture matrix.

       Since (for some weird reason) most OpenGL implementations have a very small texture matrix
       stack, and since the matrix stack also is broken on many OpenGL implementations, the
       texture matrix is always loaded into OpenGL. We do not push() and pop() matrices. "
   class SoGLNormalElement
       The SoGLNormalElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLPointSizeElement
       The SoGLPointSizeElement class changes the pointsize setting of the OpenGL render state.

       Requests from the scenegraph to change the pointsize when rendering point primitives will
       be made through this element, which forwards it to the appropriate native OpenGL call. "
   class SoGLPolygonOffsetElement
       The SoGLPolygonOffsetElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLProjectionMatrixElement
       The SoGLProjectionMatrixElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLRenderPassElement
       The SoGLRenderPassElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLShapeHintsElement
       The SoGLShapeHintsElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLUpdateAreaElement
       The SoGLUpdateAreaElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLVBOElement
       The SoGLVBOElement class is used to store VBO state.

       FIXME: write doc. "
   class SoGLViewingMatrixElement
       The SoGLViewingMatrixElement class is used to store the current viewing matrix.

       The viewing matrix contains the inverse camera coordinate system matrix. The camera
       coordinate system is built from the field values in the current SoCamera (currently either
       SoPerspectiveCamera or SoOrthographicCamera) and any transformations prior to the camera
       in the scene graph. "
   class SoGLViewportRegionElement
       The SoGLViewportRegionElement class is yet to be documented.

       FIXME: write doc. "
   class SoAccumulatedElement
       The SoAccumulatedElement class is an abstract class for storing accumulated state.

       This is the superclass of elements where new element data accumulates with older data. "
   class SoAmbientColorElement
       The SoAmbientColorElement class is yet to be documented.
   class SoAnnoText3CharOrientElement
       The SoAnnoText3CharOrientElement class is yet to be documented.

       FIXME: write doc. "
   class SoAnnoText3FontSizeHintElement
       The SoAnnoText3FontSizeHintElement class is yet to be documented.

       FIXME: write doc. "
   class SoAnnoText3RenderPrintElement
       The SoAnnoText3RenderPrintElement class is yet to be documented.

       FIXME: write doc. "
   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.
   class SoBumpMapCoordinateElement
       The SoBumpMapCoordinateElement class is yet to be documented.

       FIXME: write doc. "
   class SoBumpMapMatrixElement
       The SoBumpMapMatrixElement class is used to manage the bump map matrix stack.

       The bump map matrix is used to transform bump map coordinates before being used to map
       bump maps onto polygons. "
   class SoCacheElement
       The SoCacheElement class stores and manages the open caches.
   class SoClipPlaneElement
       The SoClipPlaneElement class is used to manage the clip plane stack.
   class SoComplexityElement
       The SoComplexityElement class contains the current shape complexity for a graph traverser.
   class SoComplexityTypeElement
       The SoComplexityTypeElement class is yet to be documented.

       FIXME: write doc. "
   class SoCoordinateElement
       The SoCoordinateElement class is yet to be documented.

       FIXME: write doc. "
   class SoCreaseAngleElement
       The SoCreaseAngleElement class stores the crease angle during a scene graph traversal.
   class SoCullElement
       The SoCullElement class is used internally for render and pick culling.

       The element holds all planes the geometry should be inside, and keeps a bitflag to signal
       which planes need to be tested. "
   class SoDecimationPercentageElement
       The SoDecimationPercentageElement class is yet to be documented.

       FIXME: write doc. "
   class SoDecimationTypeElement
       The SoDecimationTypeElement class is yet to be documented.

       FIXME: write doc. "
   class SoDepthBufferElement
       The SoDepthBufferElement controls the depth buffer settings.
   class SoDiffuseColorElement
       The SoDiffuseColorElement class is yet to be documented.

       FIXME: write doc. "
   class SoDrawStyleElement
       The SoDrawStyleElement class is yet to be documented.

       FIXME: write doc. "
   class SoElement
       SoElement is the abstract base class for all elements.
   class SoEmissiveColorElement
       The SoEmissiveColorElement class is yet to be documented.

       FIXME: write doc. "
   class SoEnvironmentElement
       The SoEnvironmentElement class is yet to be documented.

       FIXME: write doc. "
   class SoFloatElement
       SoFloatElement is an abstract base class for elements that consists of a single float
       value.

       This is the superclass of elements where the new element data replaces the old data, and
       where the data the element stores is a simple single precision floating point value. "
   class SoFocalDistanceElement
       The SoFocalDistanceElement class is yet to be documented.

       FIXME: write doc. "
   class SoFontNameElement
       The SoFontNameElement class is yet to be documented.

       FIXME: write doc. "
   class SoFontSizeElement
       The SoFontSizeElement class is yet to be documented.

       FIXME: write doc. "
   class SoInt32Element
       The SoInt32Element class is the base class for elements that simply store a 32-bit
       integer.

       This is the superclass of elements where the new element data replaces the old data, and
       where the data the element stores is a simple 32-bit integer value. "
   class SoLazyElement
       The SoLazyElement class is used to handle material and shape properties.

       So[GL]LazyElement is, as the name implies, an element that is lazy about sending things to
       OpenGL. The changes are not sent to OpenGL until SoGLLazyElement::send() is called. This
       means that you can change the state of certain attributes several times, but the state
       will only be sent to OpenGL once. "
   class SoLightAttenuationElement
       The SoLightAttenuationElement class is yet to be documented.

       FIXME: write doc. "
   class SoLightElement
       The SoLightElement class manages the currently active light sources.
   class SoLightModelElement
       The SoLightModelElement class is yet to be documented.

       FIXME: write doc. "
   class SoLinePatternElement
       The SoLinePatternElement class is yet to be documented.

       FIXME: write doc. "
   class SoLineWidthElement
       The SoLineWidthElement class changes the linewidth setting of the render state.

       Requests from the scenegraph to change the linewidth when rendering line primitives will
       be made through this element, which forwards it to the appropriate native call in the
       underlying rendering library. "
   class SoListenerDopplerElement
       The SoListenerDopplerElement holds the doppler velocity and factor of the current
       listener.

       The dopplerVelocity and dopplerFactor is set by SoListener nodes during audio rendering.
       The SoListenerDopplerElement is used when the SoVRMLSound nodes render themselves. "
   class SoListenerGainElement
       The SoListenerGainElement class stores the SoListener gain during a scene graph traversal.

       This gain is set by SoListener nodes during audio rendering. The SoListenerGainElement is
       used when the SoVRMLSound nodes render themselves. "
   class SoListenerOrientationElement
       The SoListenerOrientationElement holds the orientation of the current listener.

       This orientation is set by SoListener nodes and SoCamera Nodes during audio rendering.
       When a SoListener is visited by the SoAudioRenderAction, it will add a new
       SoListenerOrientationElement to the state, holding it's orientation and with the
       setbylistener flag set. When a SoCamera is visited by SoAudioRenderAction, it will add a
       new SoListenerOrientationElement only if there are no previous elements with the
       setbylistener flag set. "
   class SoListenerPositionElement
       The SoListenerPositionElement holds the position of the current listener.

       This position is set by SoListener nodes and SoCamera Nodes during audio rendering. When a
       SoListener is visited by the SoAudioRenderAction, it will add a new
       SoListenerPositionElement to the state, holding it's position and with the setbylistener
       flag set. When a SoCamera is visited by SoAudioRenderAction, it will add a new
       SoListenerPositionElement only if there are no previous elements with the setbylistener
       flag set. "
   class SoLocalBBoxMatrixElement
       The SoLocalBBoxMatrixElement class is yet to be documented.

       FIXME: write doc. "
   class SoMaterialBindingElement
       The SoMaterialBindingElement class is yet to be documented.

       FIXME: write doc. "
   class SoModelMatrixElement
       The SoModelMatrixElement class is used to manage the current transformation.

       SoModelMatrixElement contains the object-to-world matrix. "
   class SoMultiTextureEnabledElement
       The SoMultiTextureEnabledElement class is an element which stores whether texturing is
       enabled or not.

       Be aware that this class is an extension for Coin, and it is not available in the original
       SGI Open Inventor v2.1 API. "
   class SoMultiTextureImageElement
       The SoMultiTextureImageElement class is yet to be documented.

       FIXME: write doc. "
   class SoMultiTextureMatrixElement
       The SoMultiTextureMatrixElement class is used to manage the texture matrix stack for
       texture units > 0.

       The texture matrix is used to transform texture coordinates before being used to map
       textures onto polygons. "
   class SoNormalBindingElement
       The SoNormalBindingElement is yet to be documented.

       FIXME: write doc. "
   class SoNormalElement
       The SoNormalElement class is yet to be documented.

       FIXME: write doc. "
   class SoOverrideElement
       The SoOverrideElement maintains a list of overridable elements and a list over which
       elements should be overridden.

       Only certain elements can be overridden. "
   class SoPickRayElement
       The SoPickRayElement class is yet to be documented.

       FIXME: write doc. "
   class SoPickStyleElement
       The SoPickStyleElement is yet to be documented.

       FIXME: write doc. "
   class SoPointSizeElement
       The SoPointSizeElement changes the pointsize setting of the render state.

       Requests from the scenegraph to change the pointsize when rendering point primitives will
       be made through this element. "
   class SoPolygonOffsetElement
       The SoPolygonOffsetElement class is yet to be documented.

       FIXME: write doc. "
   class SoProfileCoordinateElement
       The SoProfileCoordinateElement class is yet to be documented.

       FIXME: write doc. "
   class SoProfileElement
       The SoProfileElement class is yet to be documented.

       FIXME: write doc. "
   class SoReplacedElement
       The SoReplacedElement class is an abstract element superclass.

       This is the superclass of all elements where the new element data replaces the old data,
       and where the data the element stores is not just a simple float or integer value. "
   class SoShapeStyleElement
       The SoShapeStyleElement class is yet to be documented.

       FIXME: write doc. "
   class SoShininessElement
       The SoShininessElement class is yet to be documented.

       FIXME: write doc. "
   class SoSoundElement
       The SoSoundElement is used for optimizing audio rendering and for turning off inactive
       SoVRMLSound nodes.
   class SoSpecularColorElement
       The SoSpecularColorElement is yet to be documented.

       FIXME: write doc. "
   class SoSwitchElement
       The SoSwitchElement class is yet to be documented.

       FIXME: write doc. "
   class SoTextOutlineEnabledElement
       The SoTextOutlineEnabledElement class is yet to be documented.

       FIXME: write doc. "
   class SoTextureCombineElement
       The SoTextureCombineElement class is yet to be documented.

       FIXME: write doc. "
   class SoTextureCoordinateBindingElement
       The SoTextureCoordinateBindingElement class is yet to be documented.

       FIXME: write doc. "
   class SoTextureOverrideElement
       The SoTextureOverrideElement makes it possible to override texture elements.
   class SoTextureQualityElement
       The SoTextureQualityElement is yet to be documented.

       FIXME: write doc. "
   class SoTextureUnitElement
       The SoTextureUnitElement class is yet to be documented.
   class SoTransparencyElement
       The SoTransparencyElement is yet to be documented.

       FIXME: write doc. "
   class SoUnitsElement
       The SoUnitsElement class is yet to be documented.

       FIXME: write doc. "
   class SoVertexAttributeBindingElement
       The SoVertexAttributeBindingElement class is yet to be documented.

       FIXME: write doc. "
   class SoViewingMatrixElement
       The SoViewingMatrixElement class stores the world-to-camera transformation.
   class SoViewportRegionElement
       The SoViewportRegionElement class is yet to be documented.

       FIXME: write doc. "
   class SoViewVolumeElement
       The SoViewVolumeElement class is yet to be documented.

       FIXME: write doc. "
   class SoWindowElement
       The SoWindowElement class is used to store current window attributes.

       In Coin, this element is not API-compatible with SGI Inventor, since it contains platform
       specific stuff, which we want to avoid. "
   class SoGeoElement
       The SoGeoElement class is yet to be documented.

       FIXME: write doc. "
   class SoGLShadowCullingElement
       The SoGLShadowCullingElement class is yet to be documented.

       FIXME: write doc. "
   class SoShadowStyleElement
       The SoShadowStyleElement class is yet to be documented.

       FIXME: write doc. "

Detailed Description

       The element classes in Coin are the containers of state information during action
       traversals of scene graphs. One element usually corresponts 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 scenegraph 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 scenegraph 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 scenegraph,
       it will request the current pointsize value from the SoState by reading off the value of
       it's 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, 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.

       The following is a complete example on how to extend Coin with your own traversal
       elements. First, the class declaration of the new element (ie 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

       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);
       }

       And a small, stand-alone 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: %s0,
                       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: %s0,
                       node->getTypeId().getName().getString(),
                       filename.getLength() == 0 ?
                       "<inlined>" : filename.getString());

         return SoCallbackAction::CONTINUE;
       }

       void
       usage(const char * appname)
       {
         (void)fprintf(stderr, "Usage: %s <modelfile.iv>0, appname);
         (void)fprintf(stderr,
                       "Lists all texture filenames in the model file,0
                       "and on which shape nodes they are used.0
                       "The purpose of this example utility is simply to0
                       "show how to create and use an extension element for0
                       "scene graph traversal.0);
       }

       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''.0, 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;
       }

Author

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