NAME
SoGetBoundingBoxAction -
The SoGetBoundingBoxAction class calculates bounding boxes for nodes
and subgraphs.
If this action is applied to a path or scene graph root, it will
calculate the bounding box and the center point of the geometry
contained within the scene.
SYNOPSIS
#include <Inventor/actions/SoGetBoundingBoxAction.h>
Inherits SoAction.
Public Types
enum ResetType { TRANSFORM = 0x1, BBOX = 0x2, ALL = TRANSFORM | BBOX
}
Public Member Functions
SoGetBoundingBoxAction (const SbViewportRegion &vp)
virtual ~SoGetBoundingBoxAction (void)
void setViewportRegion (const SbViewportRegion &newregion)
const SbViewportRegion & getViewportRegion (void) const
SbBox3f getBoundingBox (void) const
SbXfBox3f & getXfBoundingBox (void)
const SbVec3f & getCenter (void) const
void setInCameraSpace (const SbBool flag)
SbBool isInCameraSpace (void) const
void setResetPath (const SoPath *path, const SbBool resetbefore=1,
const ResetType what=ALL)
const SoPath * getResetPath (void) const
SbBool isResetPath (void) const
SbBool isResetBefore (void) const
SoGetBoundingBoxAction::ResetType getWhatReset (void) const
void checkResetBefore (void)
void checkResetAfter (void)
void extendBy (const SbBox3f &box)
void extendBy (const SbXfBox3f &box)
void setCenter (const SbVec3f ¢er, const SbBool transformcenter)
SbBool isCenterSet (void) const
void resetCenter (void)
Static Public Member Functions
static void initClass (void)
Protected Member Functions
virtual void beginTraversal (SoNode *node)
Detailed Description
The SoGetBoundingBoxAction class calculates bounding boxes for nodes
and subgraphs.
If this action is applied to a path or scene graph root, it will
calculate the bounding box and the center point of the geometry
contained within the scene.
You don’t have to apply an SoGetBoundingBoxAction to the root of a
scene. When using the action, you will get the bounding box of the node
you are applying it to and that node’s sub-tree in the scene graph (if
any).
The calculated bounding box will be in the local coordinates of that
sub-tree. If applying it to a scene graph root node, the calculated
bounding box will be in global coordinates.
The use of bounding boxes is ubiquitous within the Coin library. It is
needed for the correct execution of and for performance enhancements
during rendering, picking, caching, culling, etc.
SoSeparator nodes are aggressively caching the results of bounding box
calculations, so that they are really only re-calculated whenever the
scenegraph rooted below any SoSeparator node has been modified. This
means that applying this action to scenegraphs, or parts of
scenegraphs, should be very quick on successive runs for ’static’ parts
of the scene.
Note that the algorithm used is not guaranteed to always give an exact
bounding box: it combines bounding boxes in pairs and extends one of
them to contain the other. Since the boxes need not be parallel to the
principal axes the new box might not be a perfect fit for the box not
extended (it’s coordinate system has been changed).
Note also that what is returned from getBoundingBox() will be projected
so as to be oriented along the principal axes, which can often cause it
to become quite a lot larger than what it was before projection. For
client code to obtain the best bounding box that Coin can calculate
(and which will usually be exact), you need to use the
getXfBoundingBox() method after having applied the
SoGetBoundingBoxAction.
See also:
SoSeparator::boundingBoxCaching
Member Enumeration Documentation
enum SoGetBoundingBoxAction::ResetType This API member is considered
internal to the library, as it is not likely to be of interest to the
application programmer.
Constructor & Destructor Documentation
SoGetBoundingBoxAction::SoGetBoundingBoxAction (const SbViewportRegion &
vp) Constructor.
It might seem unnecessary to have to pass in a viewport region argument
to calculate bounding boxes, but there is a good reason for this: a few
shape nodes needs to know the viewport region to calculate their
bounding box -- these include SoText2 and SoImage, among others.
What is particular about these shapes is that they are fundamentally 2D
shapes, but they are being rendered on the screen ’surface’ as if they
were in a 3D scene. (This is possible because we can match each pixel’s
depth value against the 3D shapes in the scene.)
To compute an accurate 3D bounding box of a shape rendered in 2D on the
screen ’surface’, you need to ’de-project’ the screen-space area it
occupies to a 2D rectangle placed at some depth in the scene. This ’de-
projecting’ operation needs to know about the dimensions of the
viewport.
Also, some 3D shapes like for instance SoNurbsSurface, get slightly
distorted if there’s an SoComplexity node in the scenegraph with the
SoComplexity::value field set to SCREEN_SPACE. Then it is also
necessary to know the viewport region to find out how to accurately
calculate the bounding box of those shapes.
You would usually want to pass in a viewport region equal to the layout
of the current renderarea canvas. If you have a viewer or So available,
you can get hold of the viewport region data simply by doing
const SbViewportRegion & vpreg = viewer->getViewportRegion();
(If you don’t have a viewer or renderarea available in your application
at the point where you want to get the bounding box, it probably
doesn’t matter much what you set it to. The accuracy of the bounding
box calculation might be slightly wrong versus the actual rendered
appearance of the scene, but this is usually not noticable.)
SoGetBoundingBoxAction::~SoGetBoundingBoxAction (void) [virtual]
Destructor.
Member Function Documentation
void SoGetBoundingBoxAction::initClass (void) [static] Initializes the run-
time type system for this class, and sets up the enabled elements and
action method list.
Reimplemented from SoAction.
void SoGetBoundingBoxAction::setViewportRegion (const SbViewportRegion &
newregion) Set a new viewport region with this method, if it has
changed from the one passed in with the constructor.
const SbViewportRegion & SoGetBoundingBoxAction::getViewportRegion (void)
const Returns the viewport region used by the action instance.
SbBox3f SoGetBoundingBoxAction::getBoundingBox (void) const Returns the
projected bounding box after (or during) traversal.
SbXfBox3f & SoGetBoundingBoxAction::getXfBoundingBox (void) Returns the
bounding box and transformation matrix to global coordinates. Use after
(or during) traversal.
const SbVec3f & SoGetBoundingBoxAction::getCenter (void) const Returns
center point of scene after the action has been applied.
This might differ from the geometric center of the bounding box, as
shape nodes may ’weight’ the center point according to various criteria
(i.e. a faceset could for instance weight the center point according to
the area within its bounding box where there are more polygons).
void SoGetBoundingBoxAction::setInCameraSpace (const SbBool on) Sets
whether the returned bounding box should be calculated in the
coordinate system of the camera space or not.
SbBool SoGetBoundingBoxAction::isInCameraSpace (void) const Returns whether
the bounding box returned is to be in camera space.
void SoGetBoundingBoxAction::setResetPath (const SoPath * path, const
SbBool resetbefore = 1, const ResetType what = ALL) Forces the computed
bounding box to be reset and the transformation to be identity before
or after the tail node of path, depending on the resetbefore argument.
NULL can be specified for the path argument to disable this behavior.
See also:
getResetPath(), isResetPath(), isResetBefore(), getWhatReset()
const SoPath * SoGetBoundingBoxAction::getResetPath (void) const Returns
the reset path (or NULL).
See also:
setResetPath(), isResetPath(), isResetBefore(), getWhatReset()
SbBool SoGetBoundingBoxAction::isResetPath (void) const Returns whether a
reset path is set or not.
See also:
setResetPath(), getResetPath(), isResetBefore(), getWhatReset()
SbBool SoGetBoundingBoxAction::isResetBefore (void) const Returns whether
the bounding box and transformation is reset before or after the tail
node of the reset path.
See also:
setResetPath(), getResetPath(), isResetPath(), getWhatReset()
SoGetBoundingBoxAction::ResetType SoGetBoundingBoxAction::getWhatReset
(void) const Returns what type of reset has been specified for the
reset path.
See also:
setResetPath(), getResetPath(), isResetPath(), isResetBefore()
void SoGetBoundingBoxAction::checkResetBefore (void) This API member is
considered internal to the library, as it is not likely to be of
interest to the application programmer.
Called before node traversal of each node (from SoNode action method).
void SoGetBoundingBoxAction::checkResetAfter (void) This API member is
considered internal to the library, as it is not likely to be of
interest to the application programmer.
Called after node traversal of each node (from SoNode action method).
void SoGetBoundingBoxAction::extendBy (const SbBox3f & box) Extend bounding
box by the given box. Called from nodes during traversal.
Should usually not be of interest to application programmers, unless
you’re extending Coin with your own shapenode extension classes.
void SoGetBoundingBoxAction::extendBy (const SbXfBox3f & box) This is an
overloaded member function, provided for convenience. It differs from
the above function only in what argument(s) it accepts.
void SoGetBoundingBoxAction::setCenter (const SbVec3f & centerarg, const
SbBool transformcenter) This API member is considered internal to the
library, as it is not likely to be of interest to the application
programmer.
Set a new center point during traversal.
SbBool SoGetBoundingBoxAction::isCenterSet (void) const This API member is
considered internal to the library, as it is not likely to be of
interest to the application programmer.
Query about the center point during traversal.
void SoGetBoundingBoxAction::resetCenter (void) This API member is
considered internal to the library, as it is not likely to be of
interest to the application programmer.
Reset the scene center point during traversal.
void SoGetBoundingBoxAction::beginTraversal (SoNode * node) [protected,
virtual] This virtual method is called from SoAction::apply(), and is
the entry point for the actual scenegraph traversal.
It can be overridden to initialize the action at traversal start, for
specific initializations in the action subclasses inheriting SoAction.
Default method just calls traverse(), which any overridden
implementation of the method must do too (or call
SoAction::beginTraversal()) to trigger the scenegraph traversal.
Reimplemented from SoAction.
Author
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