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# SoVRMLLOD Class Reference
[VRML97 classes]

The SoVRMLLOD class is used to represent various levels of detail based on distance. More...

`#include <Inventor/VRMLnodes/SoVRMLLOD.h>`

Inheritance diagram for SoVRMLLOD:

List of all members.

## Public Methods
| SoVRMLLOD (void)
| SoVRMLLOD (int levels)
virtual SbBool | affectsState (void) const
void | addLevel (SoNode *level)
void | insertLevel (SoNode *level, int idx)
SoNode * | getLevel (int idx) const
int | findLevel (const SoNode *level) const
int | getNumLevels (void) const
void | removeLevel (int idx)
void | removeLevel (SoNode *level)
void | removeAllLevels (void)
void | replaceLevel (int idx, SoNode *level)
void | replaceLevel (SoNode *old, SoNode *level)
virtual void | doAction (SoAction *action)
virtual void | callback (SoCallbackAction *action)
virtual void | GLRender (SoGLRenderAction *action)
virtual void | rayPick (SoRayPickAction *action)
virtual void | getBoundingBox (SoGetBoundingBoxAction *action)
virtual void | search (SoSearchAction *action)
virtual void | write (SoWriteAction *action)
virtual void | getPrimitiveCount (SoGetPrimitiveCountAction *action)
virtual void | audioRender (SoAudioRenderAction *action)
virtual void | GLRenderBelowPath (SoGLRenderAction *action)
virtual void | GLRenderInPath (SoGLRenderAction *action)
virtual void | GLRenderOffPath (SoGLRenderAction *action)
void | addChild (SoNode *child)
void | insertChild (SoNode *child, int idx)
SoNode * | getChild (int idx) const
int | findChild (const SoNode *child) const
int | getNumChildren (void) const
void | removeChild (int idx)
void | removeChild (SoNode *child)
void | removeAllChildren (void)
void | replaceChild (int idx, SoNode *child)
void | replaceChild (SoNode *old, SoNode *child)
virtual SoChildList * | getChildren (void) const
## Static Public Methods
void | initClass (void)
## Protected Methods
virtual | ~SoVRMLLOD ()
virtual void | notify (SoNotList *list)
virtual SbBool | readInstance (SoInput *in, unsigned short flags)
virtual void | copyContents (const SoFieldContainer *from, SbBool copyConn)
virtual int | whichToTraverse (SoAction *action)

## Detailed Description

The SoVRMLLOD class is used to represent various levels of detail based on distance.

The detailed class documentation is taken verbatim from the VRML97 standard (ISO/IEC 14772-1:1997). It is copyright The Web3D Consortium, and is used by permission of the Consortium:

      LOD {
        exposedField MFNode  level    []
        field        SFVec3f center   0 0 0    # (-,)
        field        MFFloat range    []       # (0,)
      }

The LOD node specifies various levels of detail or complexity for a given object, and provides hints allowing browsers to automatically choose the appropriate version of the object based on the distance from the user. The level field contains a list of nodes that represent the same object or objects at varying levels of detail, ordered from highest level of detail to the lowest level of detail. The range field specifies the ideal distances at which to switch between the levels. Subclause 4.6.5, Grouping and children nodes (<http://www.web3d.org/technicalinfo/specifications/vrml97/part1/concepts.html#4.6.5>), contains details on the types of nodes that are legal values for level.

The center field is a translation offset in the local coordinate system that specifies the centre of the LOD node for distance calculations.

The number of nodes in the level field shall exceed the number of values in the range field by one (i.e., N+1 level values for N range values). The range field contains monotonic increasing values that shall be greater than zero. In order to calculate which level to display, first the distance is calculated from the viewer's location, transformed into the local coordinate system of the LOD node (including any scaling transformations), to the center point of the LOD node. Then, the LOD node evaluates the step function L(d) to choose a level for a given value of d (where d is the distance from the viewer position to the centre of the LOD node). Let n ranges, R0, R1, R2, ..., Rn-1, partition the domain (0, +infinity) into n+1 subintervals given by (0, R0), [R0, R1)... , [Rn-1, +infinity). Also, let n levels L0, L1, L2, ..., Ln-1 be the values of the step function function L(d). The level node, L(d), for a given distance d is defined as follows:

        L(d) = L0,   if d < R0,
             = Li+1, if Ri <= d < Ri+1, for -1 < i < n-1,
             = Ln-1, if d >= Rn-1.

Specifying too few levels will result in the last level being used repeatedly for the lowest levels of detail. If more levels than ranges are specified, the extra levels are ignored. An empty range field is an exception to this rule. This case is a hint to the browser that it may choose a level automatically to maintain a constant display rate. Each value in the range field shall be greater than the previous value.

LOD nodes are evaluated top-down in the scene graph. Only the descendants of the currently selected level are rendered. All nodes under an LOD node continue to receive and send events regardless of which LOD node's level is active. For example, if an active TimeSensor node is contained within an inactive level of an LOD node, the TimeSensor node sends events regardless of the LOD node's state.

## Constructor & Destructor Documentation

SoVRMLLOD::SoVRMLLOD | ( | void |  | ) |

| Constructor.

SoVRMLLOD::SoVRMLLOD | ( | int | levels | ) |

| Constructor. levels is the expected number of levels.

SoVRMLLOD::~SoVRMLLOD | ( |  | ) | `[protected, virtual]`

| Destructor.

## Member Function Documentation

void SoVRMLLOD::initClass | ( | void |  | ) | `[static]`

| Sets up initialization for data common to all instances of this class, like submitting necessary information to the Coin type system. Reimplemented from SoGroup.

SbBool SoVRMLLOD::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 from SoNode.

void SoVRMLLOD::addLevel | ( | SoNode * | level | ) |

| Adds a new level.

void SoVRMLLOD::insertLevel | ( | SoNode * | level,
|  | int | idx
| ) |

| Inserts a new level.

SoNode * SoVRMLLOD::getLevel | ( | int | idx | ) | const

| Returns a level.

int SoVRMLLOD::findLevel | ( | const SoNode * | node | ) | const

| Find node, and return the level index or -1 if not found.

int SoVRMLLOD::getNumLevels | ( | void |  | ) | const

| Return the number of levels.

void SoVRMLLOD::removeLevel | ( | int | idx | ) |

| Removes the level at index idx.

void SoVRMLLOD::removeLevel | ( | SoNode * | level | ) |

| Find level, and remove it if found.

void SoVRMLLOD::removeAllLevels | ( | void |  | ) |

| Remove all levels.

void SoVRMLLOD::replaceLevel | ( | int | idx,
|  | SoNode * | node
| ) |

| Replace the level at idx with node.

void SoVRMLLOD::replaceLevel | ( | SoNode * | oldnode,
|  | SoNode * | newnode
| ) |

| Find oldnode, and replace it with newnode.

void SoVRMLLOD::doAction | ( | SoAction * | action | ) | `[virtual]`

| This function performs the typical operation of a node for any action. Reimplemented from SoGroup.

void SoVRMLLOD::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. Reimplemented from SoGroup.

void SoVRMLLOD::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. Reimplemented from SoGroup.

void SoVRMLLOD::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 from SoNode.

void SoVRMLLOD::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 from SoGroup.

void SoVRMLLOD::search | ( | SoSearchAction * | action | ) | `[virtual]`

| Action method for SoSearchAction. Compares the search criteria from the action to see if this node is a match. Searching is done by matching up all criteria set up in the SoSearchAction -- if any of the requested criteria is a miss, the search is not deemed successful for the node. See also: SoSearchAction Reimplemented from SoGroup.

void SoVRMLLOD::write | ( | SoWriteAction * | action | ) | `[virtual]`

| Action method for SoWriteAction. Writes out a node object, and any connected nodes, engines etc, if necessary. Reimplemented from SoGroup.

void SoVRMLLOD::getPrimitiveCount | ( | SoGetPrimitiveCountAction * | action | ) | `[virtual]`

| Action method for the SoGetPrimitiveCountAction. Calculates the number of triangle, line segment and point primitives for the node and adds these to the counters of the action. Nodes influencing how geometry nodes calculates their primitive count also overrides this method to change the relevant state variables. Reimplemented from SoGroup.

void SoVRMLLOD::audioRender | ( | SoAudioRenderAction * | action | ) | `[virtual]`

| Action method for SoAudioRenderAction. Does common processing for SoAudioRenderAction action instances. Reimplemented from SoGroup.

void SoVRMLLOD::GLRenderBelowPath | ( | SoGLRenderAction * | action | ) | `[virtual]`

| Implements the SoAction::BELOW_PATH traversal method for the rendering action. Reimplemented from SoNode.

void SoVRMLLOD::GLRenderInPath | ( | SoGLRenderAction * | action | ) | `[virtual]`

| Implements the SoAction::IN_PATH traversal method for the rendering action. Reimplemented from SoNode.

void SoVRMLLOD::GLRenderOffPath | ( | SoGLRenderAction * | action | ) | `[virtual]`

| Implements the SoAction::OFF_PATH traversal method for the rendering action. Reimplemented from SoNode.

void SoVRMLLOD::addChild | ( | SoNode * | child | ) | `[virtual]`

| Append a child node to the list of children nodes this group node is managing. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

void SoVRMLLOD::insertChild | ( | SoNode * | child,
|  | int | idx
| ) | `[virtual]`

| Insert a child node at position newchildindex. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

SoNode * SoVRMLLOD::getChild | ( | int | idx | ) | const`[virtual]`

| Returns pointer to child node at index. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

int SoVRMLLOD::findChild | ( | const SoNode * | child | ) | const`[virtual]`

| Returns index in our list of children for child node, or -1 if node is not a child of this group node. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

int SoVRMLLOD::getNumChildren | ( | void |  | ) | const`[virtual]`

| Returns number of child nodes managed by this group. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

void SoVRMLLOD::removeChild | ( | int | idx | ) | `[virtual]`

| Remove node at childindex in our list of children. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

void SoVRMLLOD::removeChild | ( | SoNode * | child | ) | `[virtual]`

| Remove child from the set of children managed by this group node. Will decrease the reference count of child by 1. This is a convenience method. It will simply call findChild() with child as argument, and then call removeChild(int) if the child is found. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

void SoVRMLLOD::removeAllChildren | ( | void |  | ) | `[virtual]`

| Do not manage the children anymore. Will dereference all children by 1 as they are removed. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

void SoVRMLLOD::replaceChild | ( | int | idx,
|  | SoNode * | child
| ) | `[virtual]`

| Replace child at index with newChild. Dereferences the child previously at index, and increases the reference count of newChild by 1. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

void SoVRMLLOD::replaceChild | ( | SoNode * | old,
|  | SoNode * | child
| ) | `[virtual]`

| Replace oldchild with newchild. Dereferences oldchild by 1, and increases the reference count of newchild by 1. This is a convenience method. It will simply call findChild() with oldchild as argument, and call replaceChild(int, SoNode*) if the child is found. Please note that this method is not virtual in the original SGI Inventor API. Reimplemented from SoGroup.

SoChildList * SoVRMLLOD::getChildren | ( | void |  | ) | const`[virtual]`

| Returns list of children. Reimplemented from SoGroup.

void SoVRMLLOD::notify | ( | SoNotList * | list | ) | `[protected, virtual]`

| Notifies all auditors for this instance when changes are made. Reimplemented from SoNode.

SbBool SoVRMLLOD::readInstance | ( | SoInput * | in,
|  | unsigned short | flags
| ) | `[protected, virtual]`

| This method is mainly intended for internal use during file import operations. It reads a definition of an instance from the input stream in. The input stream state points to the start of a serialized / persistant representation of an instance of this class type. `TRUE` or `FALSE` is returned, depending on if the instantiation and configuration of the new object of this class type went ok or not. The import process should be robust and handle corrupted input streams by returning `FALSE`. flags is used internally during binary import when reading user extension nodes, group nodes or engines. Reimplemented from SoGroup.

void SoVRMLLOD::copyContents | ( | const SoFieldContainer * | from,
|  | SbBool | copyConn
| ) | `[protected, virtual]`

| Makes a deep copy of all data of from into this instance, except external scenegraph references if copyconnections is `FALSE`. This is the method that should be overridden by subclasses which needs to account for internal data that are not handled automatically. Make sure that when you override the copyContents() method in your extension class that you also make it call upwards to it's parent superclass in the inheritance hierarchy, as copyContents() in for instance SoNode and SoFieldContainer does important work. It should go something like this:
      void
      MyCoinExtensionNode::copyContents(const SoFieldContainer * from,
                                        SbBool copyconnections)
      {
        // let parent superclasses do their thing (copy fields, copy
        // instance name, etc etc)
        SoNode::copyContents(from, copyconnections);

        // [..then copy internal data..]
      }
Reimplemented from SoGroup.

int SoVRMLLOD::whichToTraverse | ( | SoAction * | action | ) | `[protected, virtual]`

| Returns the child to traverse based on distance to current viewpoint.

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

- SoVRMLLOD.h
- LOD.cpp