SoLevelOfDetail.h

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/*=======================================================================
** Author      : Paul S. Strauss (MMM yyyy)
** Modified by : Nick Thompson (MMM yyyy)
**=======================================================================*/
/*=======================================================================
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**=======================================================================*/
/*=======================================================================
** Modified by : VSG (MMM YYYY)
**=======================================================================*/
 
 
#ifndef  _SO_LEVEL_OF_DETAIL_
#define  _SO_LEVEL_OF_DETAIL_
 
#include <Inventor/fields/SoMFFloat.h>
#include <Inventor/nodes/SoGroup.h>
 
//
//  Class: SoLevelOfDetail
//
//  Level-of-detail group node. The children of this node typically
//  represent the same object or objects at varying levels of detail,
//  from highest detail to lowest. The size of the objects when
//  projected into the viewport is used to determine which version to
//  use (i.e., which child to traverse).
//
//  The size is computed as the area of the screen rectangle enclosing
//  the projection of the 3D bounding box that encloses all of the
//  children. When rendering, this size is compared to the values in
//  the screenArea field. If the size is greater than the first value,
//  child 0 is traversed. If it is smaller than the first, but greater
//  than the second, child 1 is traversed, and so on. If there are
//  fewer children than are required by this rule, the last child is
//  traversed. The screenArea field contains just 0 by default, so the
//  first child is always traversed.
//
//  The size calculation takes the current complexity into account. If
//  the complexity is 0 or is of type BOUNDING_BOX, the last child is
//  always traversed. If the complexity is less than .5, the computed
//  size is scaled down appropriately to use (possibly) a less
//  detailed representation. If the complexity is greater than .5, the
//  size is scaled up. At complexity 1, the first child is always used.
//
//  Picking and the callback action use the same traversal rules as
//  rendering. Bounding boxes are computed to enclose all children (as
//  is needed to compute the projected size). All other actions are
//  implemented as for SoGroup, except that SoLevelOfDetail
//  saves/restores state (like a separator) when applying any action.
//
 
class  SoLevelOfDetail : public SoGroup {
 
  SO_NODE_HEADER(SoLevelOfDetail);
 
 public:
  // Fields
  SoMFFloat           screenArea;
 
  SoLevelOfDetail();
 
  SoLevelOfDetail(int nChildren);
 
 private:
  // Implement actions:
  virtual void        doAction(SoAction *action);
  virtual void        callback(SoCallbackAction *action);
  virtual void        GLRender(SoGLRenderAction *action);
  virtual void        rayPick(SoRayPickAction *action);
 
 private:
  static void         initClass();
  static void         exitClass();
 
 private:
  virtual ~SoLevelOfDetail();
 
 private:
  // This action is used to compute the screen-space bbox
  static SoGetBoundingBoxAction      *bboxAction;
};
 
#endif /* _SO_LEVEL_OF_DETAIL_ */