---
name: "SoLevelOfDetail"
section: "3"
platform: "linux"
package: "coin"
version: "1:4.0.10-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/SoLevelOfDetail"
---

# SoLevelOfDetail(3)

The SoLevelOfDetail class is used to choose a child based on projected size.

## NAME

SoLevelOfDetail - The **SoLevelOfDetail** class is used to choose a child based on projected size.

## SYNOPSIS

\#include \<Inventor/nodes/SoLevelOfDetail.h\>

Inherits **SoGroup**.

### Public Member Functions

virtual **SoType** **getTypeId** (void) const\
 **SoLevelOfDetail** (void)\
 **SoLevelOfDetail** (int numchildren)\
 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 **audioRender** (**SoAudioRenderAction** \*action)\
 virtual void **notify** (**SoNotList** \*nl)\

Public Member Functions inherited from **SoGroup** **SoGroup** (void)\
 **SoGroup** (int nchildren)\
 virtual void **addChild** (**SoNode** \*node)\
 virtual void **insertChild** (**SoNode** \*child, int newchildindex)\
 virtual **SoNode** \* **getChild** (int index) const\
 virtual int **findChild** (const **SoNode** \*node) const\
 virtual int **getNumChildren** (void) const\
 virtual void **removeChild** (int childindex)\
 virtual void **removeChild** (**SoNode** \*child)\
 virtual void **removeAllChildren** (void)\
 virtual void **replaceChild** (int index, **SoNode** \*newchild)\
 virtual void **replaceChild** (**SoNode** \*oldchild, **SoNode** \*newchild)\
 virtual void **getMatrix** (**SoGetMatrixAction** \*action)\
 virtual void **handleEvent** (**SoHandleEventAction** \*action)\
 virtual void **pick** (**SoPickAction** \*action)\
 virtual void **search** (**SoSearchAction** \*action)\
 virtual void **write** (**SoWriteAction** \*action)\
 virtual void **getPrimitiveCount** (**SoGetPrimitiveCountAction** \*action)\
 virtual **SoChildList** \* **getChildren** (void) const\
 virtual void **addWriteReference** (**SoOutput** \*out, SbBool isfromfield=FALSE)\

Public Member Functions inherited from **SoNode** void **setOverride** (const SbBool state)\
 SbBool **isOverride** (void) const\
 void **setNodeType** (const **NodeType** type)\
 **NodeType** **getNodeType** (void) const\
 virtual **SoNode** \* **copy** (SbBool copyconnections=FALSE) const\
 virtual SbBool **affectsState** (void) const\
 virtual void **GLRenderBelowPath** (**SoGLRenderAction** \*action)\
 virtual void **GLRenderInPath** (**SoGLRenderAction** \*action)\
 virtual void **GLRenderOffPath** (**SoGLRenderAction** \*action)\
 virtual void **grabEventsSetup** (void)\
 virtual void **grabEventsCleanup** (void)\
 virtual void **startNotify** (void)\
 SbUniqueId **getNodeId** (void) const\
 virtual void **writeInstance** (**SoOutput** \*out)\
 virtual **SoNode** \* **addToCopyDict** (void) const\
 virtual **SoFieldContainer** \* **copyThroughConnection** (void) const\

Public Member Functions inherited from **SoFieldContainer** void **setToDefaults** (void)\
 SbBool **hasDefaultValues** (void) const\
 SbBool **fieldsAreEqual** (const **SoFieldContainer** \*container) const\
 void **copyFieldValues** (const **SoFieldContainer** \*container, SbBool copyconnections=FALSE)\
 SbBool **set** (const char \*const fielddata)\
 void **get** (**SbString** &fielddata)\
 virtual int **getFields** (**SoFieldList** &l) const\
 virtual int **getAllFields** (**SoFieldList** &l) const\
 virtual **SoField** \* **getField** (const **SbName** &name) const\
 virtual **SoField** \* **getEventIn** (const **SbName** &name) const\
 virtual **SoField** \* **getEventOut** (const **SbName** &name) const\
 SbBool **getFieldName** (const **SoField** \*const field, **SbName** &name) const\
 SbBool **enableNotify** (const SbBool flag)\
 SbBool **isNotifyEnabled** (void) const\
 SbBool **set** (const char \*fielddata, **SoInput** \*input)\
 void **get** (**SbString** &fielddata, **SoOutput** \*out)\
 virtual SbBool **validateNewFieldValue** (**SoField** \*field, void \*newval)\
 SbBool **getIsBuiltIn** (void) const\
 virtual void **getFieldsMemorySize** (size\_t &managed, size\_t &unmanaged) const\
 void **setUserData** (void \*userdata) const\
 void \* **getUserData** (void) const\

Public Member Functions inherited from **SoBase** void **ref** (void) const\
 void **unref** (void) const\
 void **unrefNoDelete** (void) const\
 int32\_t **getRefCount** (void) const\
 void **touch** (void)\
 SbBool **isOfType** (**SoType** type) const\
 Returns TRUE if the type of this object is either of the same type or inherited from *type*.  virtual **SbName** **getName** (void) const\
 virtual void **setName** (const **SbName** &newname)\
 void **addAuditor** (void \*const auditor, const **SoNotRec::Type** type)\
 void **removeAuditor** (void \*const auditor, const **SoNotRec::Type** type)\
 const **SoAuditorList** & **getAuditors** (void) const\
 SbBool **shouldWrite** (void)\
 void **assertAlive** (void) const\

### Static Public Member Functions

static **SoType** **getClassTypeId** (void)\
 static void **initClass** (void)\
 Sets up initialization for data common to all instances of this class, like submitting necessary information to the Coin type system.

Static Public Member Functions inherited from **SoGroup** static **SoType** **getClassTypeId** (void)\
 static void **initClass** (void)\
 Sets up initialization for data common to all instances of this class, like submitting necessary information to the Coin type system.

Static Public Member Functions inherited from **SoNode** 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)\
 Sets up initialization for data common to all instances of this class, like submitting necessary information to the Coin type system.     static void **initClasses** (void)\
 static SbUniqueId **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)\

Static Public Member Functions inherited from **SoFieldContainer** static void **initClass** (void)\
 Sets up initialization for data common to all instances of this class, like submitting necessary information to the Coin type system.     static **SoType** **getClassTypeId** (void)\
 This static method returns the **SoType** object associated with objects of this class.     static void **cleanupClass** (void)\
 static void **initCopyDict** (void)\
 static void **addCopy** (const **SoFieldContainer** \*orig, const **SoFieldContainer** \*copy)\
 static **SoFieldContainer** \* **checkCopy** (const **SoFieldContainer** \*orig)\
 static **SoFieldContainer** \* **findCopy** (const **SoFieldContainer** \*orig, const SbBool copyconnections)\
 static void **copyDone** (void)\

Static Public Member Functions inherited from **SoBase** static void **initClass** (void)\
 Sets up initialization for data common to all instances of this class, like submitting necessary information to the Coin type system.  static **SoType** **getClassTypeId** (void)\
 This static method returns the **SoType** object associated with objects of this class.  static void **addName** (**SoBase** \*const base, const char \*const name)\
 static void **removeName** (**SoBase** \*const base, const char \*const name)\
 static void **incrementCurrentWriteCounter** (void)\
 static void **decrementCurrentWriteCounter** (void)\
 static **SoBase** \* **getNamedBase** (const **SbName** &name, **SoType** type)\
 static int **getNamedBases** (const **SbName** &name, **SoBaseList** &baselist, **SoType** type)\
 static SbBool **read** (**SoInput** \*input, **SoBase** \*&base, **SoType** expectedtype)\
 static void **setInstancePrefix** (const **SbString** &c)\
 static void **setTraceRefs** (SbBool trace)\
 static SbBool **getTraceRefs** (void)\
 static SbBool **connectRoute** (**SoInput** \*input, const **SbName** &fromnodename, const **SbName** &fromfieldname, const **SbName** &tonodename, const **SbName** &tofieldname)\
 static SbBool **readRoute** (**SoInput** \*input)\

### Public Attributes

**SoMFFloat** **screenArea**\

### Protected Member Functions

virtual const **SoFieldData** \* **getFieldData** (void) const\
 virtual **~SoLevelOfDetail** ()\

Protected Member Functions inherited from **SoGroup** virtual **~SoGroup** ()\
 virtual SbBool **readInstance** (**SoInput** \*in, unsigned short flags)\
 virtual SbBool **readChildren** (**SoInput** \*in)\
 virtual void **copyContents** (const **SoFieldContainer** \*from, SbBool copyconnections)\
 virtual **SoNotRec** **createNotRec** (void)\
 void **setOperation** (const **SoNotRec::OperationType** opType=SoNotRec::UNSPECIFIED, const **SoNode** \*cc=NULL, const **SoNode** \*pc=NULL, const int ci=-1)\

Protected Member Functions inherited from **SoNode** **SoNode** (void)\
 virtual **~SoNode** ()\

Protected Member Functions inherited from **SoFieldContainer** **SoFieldContainer** (void)\
 virtual **~SoFieldContainer** ()\

Protected Member Functions inherited from **SoBase** **SoBase** (void)\
 virtual **~SoBase** ()\
 virtual void **destroy** (void)\
 SbBool **hasMultipleWriteRefs** (void) const\
 SbBool **writeHeader** (**SoOutput** \*out, SbBool isgroup, SbBool isengine) const\
 void **writeFooter** (**SoOutput** \*out) const\
 virtual const char \* **getFileFormatName** (void) const\

### Static Protected Member Functions

static const **SoFieldData** \*\* **getFieldDataPtr** (void)\

Static Protected Member Functions inherited from **SoGroup** static const **SoFieldData** \*\* **getFieldDataPtr** (void)\

Static Protected Member Functions inherited from **SoNode** 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)\

Static Protected Member Functions inherited from **SoBase** static uint32\_t **getCurrentWriteCounter** (void)\
 static void **staticDataLock** (void)\
 static void **staticDataUnlock** (void)\

### Additional Inherited Members

Public Types inherited from **SoNode** 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, **INVENTOR\_6\_0** = 0x10000, **COIN\_4\_0** = 0x20000 }\

Protected Types inherited from **SoBase** enum **BaseFlags** { **IS\_ENGINE** = 0x01, **IS\_GROUP** = 0x02 }\

Protected Attributes inherited from **SoGroup** **SoChildList** \* **children**\

Protected Attributes inherited from **SoNode** SbUniqueId **uniqueId**\

Protected Attributes inherited from **SoFieldContainer** SbBool **isBuiltIn**\

Static Protected Attributes inherited from **SoNode** static SbUniqueId **nextUniqueId** = 1\
 static int **nextActionMethodIndex** = 0\

## Detailed Description

The **SoLevelOfDetail** class is used to choose a child based on projected size.

A level-of-detail mechanism is typically used by application programmers to assist the library in speeding up the rendering.

The way a level-of-detail mechanism works is basically like this:

Several versions of varying complexity of *the* *same* geometry / shape is provided by the application programmer in sorted order from "most complex" to "least complex" (where "complex" in this context should be taken to mean more or less detailed in the number of polygons / shapes used for rendering it).

The runtime rendering system then, upon scene graph traversal, will on-the-fly calculate either the distance from the camera to the 3D-model in question, or the number of pixels in the screen projection of the 3D-model. This value is then used to decide which version of the model to actually render: as the model is moved farther away from the camera, a less detailed version of the model is used. And vice versa, as the model moves closer to the camera, more and more detailed versions of it are rendered.

This is under many different circumstances a very effective way to let the application programmer assist to *profoundly* optimize the rendering of her 3D-scene.

There is of course a trade-off with the level-of-detail technique: more versions of the same 3D model means the scene graph will use up more application memory resources. Also, generating the set of less and less detailed versions of a 3D model from the original is often not a trivial task to do properly. The process is often assisted by software like what Kongsberg Oil & Gas Technologies offers in their \<a href="http://www.rational-reducer.com\>Rational Reducer\</a\> package.The SoLevelOfDetail node implements the "projected size" varietylevel-of-detail technique (as opposed to the "object distance"technique, as done by the SoLOD node).The node works by comparing the current projected size of thesmallest rectangle covering the bounding box of its child geometry.Along with this set of models of the same shape, a specification ofwhen to switch between them is also provided.Example scene graph layout:@code LevelOfDetail {   screenArea \[ 2000, 500, 50 \]   DEF version-0 Separator {     # most complex / detailed / heavy version of subgraph   }   DEF version-1 Separator {     # less complex version of subgraph   }   DEF version-2 Separator {     # even less complex version of subgraph   }   DEF version-3 Separator {     # simplest / "lightest" version of subgraph   }}\\endcodeThe way the above sub-scene graph would work would be the following:if the rectangular area around the model's projected bounding boxcovers \\e more than 2000 pixels (meaning it will be up pretty closeto the camera), the most complex version of the model (\\c version-0)would be traversed (and rendered, of course). If the projected areawould be \\e between 500 and 2000 pixels, the \\c version-1 modelwould be used. Ditto if the projected area was between 50 and 500pixels, the \\c version-2 version of the model would beused. Finally, if the projected bounding box area would be \\e lessthan 50 square pixels, the presumably least detailed version of themodel would be used.(A common "trick" is to let the last of the SoLevelOfDetail node'schildren be just an empty subgraph, so no geometry will be renderedat all if the model is sufficiently far away. This will of coursehave a positive effect on the total rendering time for the completescene graph.)Note that the SoLevelOfDetail::screenArea vector will be influencedby preceding SoComplexity nodes in the following way: ifSoComplexity::value is set from 0.0 up to 0.5, lower detail levelsthan normal will be selected for traversal. If SoComplexity::valueis above 0.5, higher level details than normal will be used. AnSoComplexity::value equal to 1.0 will cause the first child ofSoLevelOfDetail to always be used.As mentioned above, there is one other level-of-detail node in theCoin library: SoLOD. The difference between that one and this isjust that instead of projected bounding box area, SoLOD uses thedistance between the camera and the object to find out when toswitch between the different model versions.Using SoLOD is faster, since figuring out the projected bounding boxarea needs a certain amount of calculations. But usingSoLevelOfDetail is often "better", in the sense that it's really a model's size and visibility in the viewport that determines whether we could switch to a less complex version without losing enough detail that it gives a noticeable visual degradation.

**FILE FORMAT/DEFAULTS:**

```
LevelOfDetail {
    screenArea 0
}
```

**See also**

**SoLOD**

## Constructor & Destructor Documentation

### SoLevelOfDetail::SoLevelOfDetail (void )

Default constructor.

### SoLevelOfDetail::SoLevelOfDetail (int numchildren)

Constructor.

The argument should be the approximate number of children which is expected to be inserted below this node. The number need not be exact, as it is only used as a hint for better memory resource allocation.

### SoLevelOfDetail::~SoLevelOfDetail () \[protected\], \[virtual\]

Destructor.

## Member Function Documentation

### SoType SoLevelOfDetail::getClassTypeId (void ) \[static\]

This static method returns the **SoType** object associated with objects of this class.

### SoType SoLevelOfDetail::getTypeId (void ) const \[virtual\]

Returns the type identification of an object derived from a class inheriting **SoBase**. This is used for runtime type checking and "downward" casting.

Reimplemented from **SoGroup**.

### const SoFieldData \*\* SoLevelOfDetail::getFieldDataPtr (void ) \[static\], \[protected\]

*This API member is considered internal to the library, as it is not likely to be of interest to the application programmer.*\

 Returns the **SoFieldData** class which holds information about fields in this node.

### const SoFieldData \* SoLevelOfDetail::getFieldData (void ) const \[protected\], \[virtual\]

Returns a pointer to the class-wide field data storage object for this instance. If no fields are present, returns NULL.

Reimplemented from **SoGroup**.

### void SoLevelOfDetail::doAction (SoAction \* action) \[virtual\]

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

Reimplemented from **SoGroup**.

### void SoLevelOfDetail::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 SoLevelOfDetail::GLRender (SoGLRenderAction \* action) \[virtual\]

Action method for the **SoGLRenderAction**.

This is called during rendering traversals. Nodes influencing the rendering state in any way or want to throw geometry primitives at OpenGL override this method.

Reimplemented from **SoGroup**.

### void SoLevelOfDetail::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 override this method.

Reimplemented from **SoNode**.

### void SoLevelOfDetail::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 calculate their bounding box also override this method to change the relevant state variables.

Reimplemented from **SoGroup**.

### void SoLevelOfDetail::audioRender (SoAudioRenderAction \* action) \[virtual\]

Action method for **SoAudioRenderAction**.

Does common processing for **SoAudioRenderAction** *action* instances.

Reimplemented from **SoGroup**.

### void SoLevelOfDetail::notify (SoNotList \* l) \[virtual\]

Notifies all auditors for this instance when changes are made.

Reimplemented from **SoNode**.

## Member Data Documentation

### SoMFFloat SoLevelOfDetail::screenArea

The screen area limits for the children. See usage example in main class documentation of **SoLevelOfDetail** for an explanation of how this vector should be set up correctly.

By default this vector just contains a single value 0.0f.

## Author

Generated automatically by Doxygen for Coin from the source code.