[osg-users] Refactoring DatabasePagerNeedToRemovestringflagging technique

Wojciech Lewandowski lewandowski at ai.com.pl
Mon Nov 23 09:35:55 PST 2009


Thanks Glenn. I will look at this. Wojtek
  ----- Original Message ----- 
  From: Glenn Waldron 
  To: OpenSceneGraph Users 
  Sent: Monday, November 23, 2009 5:41 PM
  Subject: Re: [osg-users] Refactoring DatabasePagerNeedToRemovestringflagging technique


  On Mon, Nov 23, 2009 at 11:10 AM, Robert Osfield <robert.osfield at gmail.com> wrote:

    Hi Wojtek,

    On Mon, Nov 23, 2009 at 2:34 PM, Wojciech Lewandowski

    <lewandowski at ai.com.pl> wrote:

    > But I would strongly defend merits of arguments in the post. You say we did
    > wrong, but whats you recommendation on mixing many intersections with
    > rendering ?  Its very common scenario. How  should we tackle it, if current
    > approach is wrong ?


    The right approach is a difficult one.  Getting a paged scene graph to
    work with intersections at highest resolutions and at the same time
    manage things for rendering with requires just the appropriate LOD
    child for the needs of visuals is awkward.   I know often vis-sim apps
    don't even try to mix the two, and have a separate process entirely
    for dealing intersections as for doing the visuals.  Some sims even
    run the visuals and intersection testing on entirely different
    machines.  Other sims use entirely separate databases for intersection
    testing and visuals.  Then there are others that use a height field
    for height above terrain testing...


  Wojtek,

  The "keep it separate" approach is what we use in osgEarth. The idea is to fetch terrain tiles directly, based on your target sampling resolution, instead of traversing the whole LOD hierarchy. Take a took at the ElevationManager utility. Perhaps it can provide some inspiration:

  http://wush.net/trac/osgearth/browser/trunk/src/osgEarthUtil/ElevationManager

  Glenn
   




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