NAME
SoLOD -
The SoLOD class is used to choose a child based distance between viewer
and object.
The class documentation for the SoLOD node class would be similar
enough to that of SoLevelOfDetail that we will refer you to look at
that one first. It will explain the general principles of what a level-
of-detail mechanism is, and why and how to use it.
SYNOPSIS
#include <Inventor/nodes/SoLOD.h>
Inherits SoGroup.
Public Member Functions
SoLOD (void)
SoLOD (int numchildren)
virtual void doAction (SoAction *action)
virtual void callback (SoCallbackAction *action)
virtual void GLRender (SoGLRenderAction *action)
virtual void GLRenderBelowPath (SoGLRenderAction *action)
virtual void GLRenderInPath (SoGLRenderAction *action)
virtual void GLRenderOffPath (SoGLRenderAction *action)
virtual void rayPick (SoRayPickAction *action)
virtual void getBoundingBox (SoGetBoundingBoxAction *action)
virtual void getPrimitiveCount (SoGetPrimitiveCountAction *action)
virtual void audioRender (SoAudioRenderAction *action)
virtual void notify (SoNotList *nl)
Static Public Member Functions
static void initClass (void)
Public Attributes
SoMFFloat range
SoSFVec3f center
Protected Member Functions
virtual ~SoLOD ()
virtual int whichToTraverse (SoAction *)
Detailed Description
The SoLOD class is used to choose a child based distance between viewer
and object.
The class documentation for the SoLOD node class would be similar
enough to that of SoLevelOfDetail that we will refer you to look at
that one first. It will explain the general principles of what a level-
of-detail mechanism is, and why and how to use it.
(The main difference between SoLOD and SoLevelOfDetail is that SoLOD
uses the speedier ’distance-to-viewer’ technique for implementing
level-of-detail functionality, versus the more correct (but potentially
slower) ’projected-bbox-area’ technique used by SoLevelOfDetail.)
Here’s a mockup example (in Inventor file format style, but easily
converted to code) that shows how to use this node:
LOD {
range [ 10, 20, 30, 40 ]
Sphere { }
Cylinder { }
Cone { }
Cube { }
Info { }
}
For the sub-scenegraph above, when the LOD-object is less than 10 units
away from the viewpoint camera, an SoSphere will be shown. For
distances 10 - 20 units away, this will be changed to the SoCylinder,
and so on. For distances of more than 40 units from the camera, an
SoInfo node will be traversed / rendered -- ie, nothing will be shown.
(This is a common ’trick’ used to optimize rendering when models get
far enough away from the camera that we want to remove them
completely).
Note that when using an SoOrthographicCamera in the examiner viewers of
the SoQt, SoWin and SoXt libraries, it will seem like the SoLOD node is
not working when using the ’Zoom’ functionality. What happens is that
an SoOrthographicCamera is not actually moved, the ’zoom’ effect is
accomplished simply by changing its height-of-view setting (i.e. the
value of the SoOrthographicCamera::height field), but its position
remains constant. So the distance to the camera will not change, which
means SoLOD will pick the same child, no matter how much one ’zooms’.
(The SoLevelOfDetail node uses the screen space area of the object to
decide when to switch children, so that node will still work with
SoOrthographicCamera.)
FILE FORMAT/DEFAULTS:
LOD {
center 0 0 0
range [ ]
}
Since:
Inventor 2.1
See also:
SoLevelOfDetail
Constructor & Destructor Documentation
SoLOD::SoLOD (void) Default constructor.
SoLOD::SoLOD (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.
SoLOD::~SoLOD () [protected, virtual] Destructor.
Member Function Documentation
void SoLOD::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.
void SoLOD::doAction (SoAction * action) [virtual] This function performs
the typical operation of a node for any action.
Reimplemented from SoGroup.
void SoLOD::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 SoLOD::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 SoLOD::GLRenderBelowPath (SoGLRenderAction * action) [virtual]
Implements the SoAction::BELOW_PATH traversal method for the rendering
action.
Reimplemented from SoNode.
void SoLOD::GLRenderInPath (SoGLRenderAction * action) [virtual] Implements
the SoAction::IN_PATH traversal method for the rendering action.
Reimplemented from SoNode.
void SoLOD::GLRenderOffPath (SoGLRenderAction * action) [virtual]
Implements the SoAction::OFF_PATH traversal method for the rendering
action.
Reimplemented from SoNode.
void SoLOD::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 SoLOD::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 SoLOD::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 SoLOD::audioRender (SoAudioRenderAction * action) [virtual] Action
method for SoAudioRenderAction.
Does common processing for SoAudioRenderAction action instances.
Reimplemented from SoGroup.
void SoLOD::notify (SoNotList * l) [virtual] Notifies all auditors for this
instance when changes are made.
Reimplemented from SoNode.
int SoLOD::whichToTraverse (SoAction * action) [protected, virtual] Returns
the child to traverse based on the ranges in SoLOD::range. Will clamp
to index to the number of children. This method will return -1 if no
child should be traversed. This will only happen if the node has no
children though.
Member Data Documentation
SoMFFloat SoLOD::range The distance ranges which decides when to use each
child for traversal / rendering. See usage example in main class
documentation of SoLOD for an explanation of how this vector should be
set up correctly.
By default this vector just contains a single value 0.0f.
SoSFVec3f SoLOD::center This vector represents an offset within the object
from the geometric center point to the center point the application
programmer would actually like the distance between the viewer and the
object to be calculated from.
Default value is [0, 0, 0]. It is usually not necessary to change this
field.
Author
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