[osg-users] OSG in non-continuous rendering

Robert Osfield robert.osfield at gmail.com
Thu Oct 18 23:21:18 PDT 2007


Hi Faraz,

W.r.t continous (frame driven) vs events driven, the OSG can do both,
as its up to your app to call Viewer::frame() (unless you use the high
level Viewer::run to run the frame loop).   The main problem with
going event driven is that animations won't update continously and any
database paging would become rather slow - if you don't use either of
these it should be fine for an interactive app.

W.r.t coordinate system just place a MatrixTransform above you models
to place them in large coord system.  The models should have a local
origin to keep floats nice a small.

Robert.

On 10/19/07, Faraz Ravi <faraz at igloo-soft.com> wrote:
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> Hi All
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> I'm taking a look at OSG and I really like what it offers. I am looking to
> possibly use it in a CAD like environment where it is windowed and there is
> no continuous rendering loop. Rendering is performed as and when it is
> required, for example if the viewpoint is changed. This is important since
> the scene may take 0.5s or more to render and is degraded for higher fps
> during movement.
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> I've adapted the fltk example to test this and it seems to work fine. So
> what I wanted to know is:
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> 1.       Does OSG have any internal dependencies on a continuous rendering
> loop?
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> 2.       Are there any known uses of OSG like this, or in a similar
> environment?
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> 3.       Is there anything else I need to be aware of if I am doing this?
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> Note that when there is a continuous rendering loop in the fltk example the
> UI performance is hit badly, ie menus slow down and so on – it would also
> hit any CPU processes so this is not really a realistic model for my
> application.
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> I noticed osgDirector uses a continuous loop with wxWidgets, seems to work
> quite well. I guess its rendering in another thread.
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> On a different note does anyone know what method OSG uses to manage
> coordinate truncation / scaling issues when dealing with the teapot in the
> desert like scenario? Does it performance multiple passes or is there a
> different coordinate frame for each scale? Lets say I wanted to show a
> building in a large landscape without losing coordinate precision in the
> building for example.
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> Thanks for any help
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>
> Faraz
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