[osg-users] PagedLOD glitches

[Robert Osfield]

Hi Andreas,

The PagedLOD is designed to only switch to a higher level of detail
once that level of detail is merged, it'll fallback automatically to
next highest level of detail automatically until this happens.  This
"should" mean that you never get gaps where neither LOD is available.

I've done lots of testing of PageLOD over the years and haven't come
across issue like you describe, however, a probably haven't come
across a database constructed in the particular way you have probably
built yours with so perhaps there is something in your database that
is introducing the problem.

Robert.

Robert.

On 26 August 2016 at 15:18, Andreas Ekstrand
<andreas.ekstrand at remograph.com> wrote:
> Hi Robert,
>
> The glitches are purely visual. I have no overlapping ranges, my problem is
> the opposite - when I'm moving towards a level and the range switches, it
> takes a while to load the high level and the low level is switched off.
> While loading, there is just empty space for a while until the high level
> has been loaded and is visualized.
>
> Attached is an attempt to illustrate the problem. When moving from position
> 1 to 2, the middle level is switched out and although the high level is
> within its range it takes a while to load it, so there is a hole until it's
> finally been loaded in 3. Note that I don't have to move the viewer between
> 2 and 3, just wait for the loading. I would want the middle level to be
> visible until the high level is actually loaded.
>
> Maybe I'm misunderstanding something about PagedLOD, the database pager, or
> how to create quad-tree scene graphs for it to work properly? I have only
> developed these things myself before in other projects, and actually not
> used PagedLOD until now.
>
> Regards,
> Andreas
>
>
>
> On 2016-08-26 15:58, Robert Osfield wrote:
>
> Hi Andreas,
>
> On 26 August 2016 at 12:09, Andreas Ekstrand
> <andreas.ekstrand at remograph.com> wrote:
>
> Is there any way to avoid glitches in the PagedLOD during loading of the
> higher level after the lower level has switched out?
>
> Are we talking just a visual glitch or a frame rate drop, or both?
>
> When flying over my
> quad-tree terrain the tiles are flickering and the background color is
> visible a short while before the higher level has been loaded.
>
> One can of course override and implement logic that waits to switch the
> lower level of until the higher has been loaded, but maybe I have missed
> some existing setting?
>
> The logic in PageLOD::traverse() that decides between which LOD's to
> display depends entirely on the LOD ranges used for each child, if the
> ranges are distinct then no two children of a single PageLOD will be
> displayed at the same time.
>
> If you built the database such that the PageLOD's overlap a bit then
> you have a case where both a lower level of detail and higher level of
> detail could be visible at once.  Given your description this sounds
> like it may be possibility.  I wouldn't recommend building PageLOD
> databases with overlapping LOD range though - they can abut but
> shouldn't overlap.
>
> The other possibility might be display latency, or if you have some
> kinds of higher level effect for visually blending between LOD levels.
>
> Robert.
> _______________________________________________
> osg-users mailing list
> osg-users at lists.openscenegraph.org
> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>
>
>
> _______________________________________________
> osg-users mailing list
> osg-users at lists.openscenegraph.org
> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>