[osg-users] OSG in non-continuous rendering

Ralph Kern usenet04 at rk-se.de
Thu Oct 18 23:19:22 PDT 2007


Faraz Ravi schrieb:
> 1.       Does OSG have any internal dependencies on a continuous
> rendering loop?
> 

For a static scene in a CAD environment, the answer is 'no'. Continuous
rendering is needed for the "immersion effect" for VR systems, so for a
smooth animation or smooth camera movements. For animation, OSG has an
internal notion of "frame time".

> 2.       Are there any known uses of OSG like this, or in a similar
> environment?
> 
> 3.       Is there anything else I need to be aware of if I am doing this?

Look out for window repaint events. You need to rerender your scene
then, or you have to buffer your rendering output using FBO's or pbuffers.

> 
> 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.
> 

Geometry is internally processed in float precision by most OpenGL
implementations, but transformations are double precision. So put your
geometry in local coordinate systems with an origin nearby your geometry
and transform them to the correct places.

This is also valuable for your database design, as anyways floats or
doubles loose precision when they have large values.

regards Ralph




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