[osg-users] Question about OSG rasterisation relevant questions.

Chris Hanson xenon at alphapixel.com
Thu Dec 27 09:04:38 PST 2018

On Thu, Dec 27, 2018 at 12:48 PM Zachary1234 <poweruserm at live.com.au> wrote:

> I just wanted to know so that I am aware if  need to instantiate class
> object separately and submit them, or if this "faculties" of the rendering
> pipeline are already inside, behind the scenes, automatically.

  Everything I described as far as the bounding-sphere clipping is done

> -I had guessed that rear face culling was something inside, and automatic.

It is, unless you disable it.

> -I take it to be the case that pre-draw coincidence occlusion doesn't
> happen at all, and that towards a camera, things are just draw over things,
> certainly to start, by default.  Is this much true?

Yes. They are not drawn in any particular order, OpenGL normally just
relies on the Z buffer to sort out obscuring things.

If you have transparent/translucent objects, you can tell OSG to sort them
by distance so that they are drawn furthest to nearest, in order to make
transparency sort of work.

If you want to use OpenGL's occlusion culling extensions, there are some
examples out there of how to do this in OSG. However, usually you need some
fairly complex objects with a lot of depth layers before it's worthwhile.

> -There is a 2D user interface widgets package that now comes as part of
> OSG.  IS this just an inclusion of wxwidgets?  What is is the name of this
> toolkit?

  It is not wxWidgets. It's a simple 2D widget system. I don't know too
many people using it.

Chris 'Xenon' Hanson, omo sanza lettere. Xenon at AlphaPixel.com
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