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Question about OSG rasterisation relevant questions.


 
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Zachary1234
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Joined: 20 Nov 2018
Posts: 24

PostPosted: Mon Dec 24, 2018 6:06 am    Post subject:
Question about OSG rasterisation relevant questions.
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To who it may concern,

Merry Christmas and a Happy New Year.


I have the following two questions about the OSG library.


In the context of two 3D objects in a lit 3D universe,
with one camera pointing to view those two objects,



-Is there default backface culling elimination that goes on
by default before objects are sent to screen, in OSG?



-Are there any default occluding calculations that
go on with multiple relative 3D objects in an OSG 3D Universe
before things are sent to screen? Is this calculating, at default,
entirely ignored, or partly ignored?



Happy New Year!

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Chris Hanson
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PostPosted: Mon Dec 24, 2018 1:13 pm    Post subject:
Question about OSG rasterisation relevant questions.
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There is object-based bounding sphere culling before objects are sent to be drawn by the OpenGL pipeline. This isn't something you can normally disable,it's part of building OSG's Render List, which is which is the list of objects and primitives actually sent to OpenGL

When the objects are drawn, OpenGL usually performs primitive level face culling based on the vertex winding order. You can turn off OpenGL's culling if needed.




Can you elaborate on why you need these answers, perhaps we can be more helpful.


On Mon, Dec 24, 2018 at 7:06 AM A Z < (
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Quote:
To who it may concern,

Merry Christmas and a Happy New Year.


I have the following two questions about the OSG library.


In the context of two 3D objects in a lit 3D universe,
with one camera pointing to view those two objects,



-Is there default backface culling elimination that goes on
by default before objects are sent to screen, in OSG?



-Are there any default occluding calculations that
go on with multiple relative 3D objects in an OSG 3D Universe
before things are sent to screen?  Is this calculating, at default,
entirely ignored, or partly ignored?



Happy New Year!




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Zachary1234
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Joined: 20 Nov 2018
Posts: 24

PostPosted: Wed Dec 26, 2018 2:41 am    Post subject:
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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.

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

-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?

-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?

Happy New Year, and thanks for the answers!
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Chris Hanson
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PostPosted: Thu Dec 27, 2018 5:05 pm    Post subject:
Question about OSG rasterisation relevant questions.
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On Thu, Dec 27, 2018 at 12:48 PM Zachary1234 < (
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Quote:
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 automatically.
 
Quote:
-I had guessed that rear face culling was something inside, and automatic.


It is, unless you disable it.
 
Quote:
-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.
 
Quote:
-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.
 

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Chris 'Xenon' Hanson, omo sanza lettere. http://www.alphapixel.com/
Training • Consulting • Contracting
3D • Scene Graphs (Open Scene Graph/OSG) • OpenGL 2 • OpenGL 3 • OpenGL 4 • GLSL • OpenGL ES 1 • OpenGL ES 2 • OpenCL
Legal/IP • Forensics • Imaging • UAVs • GIS • GPS • osgEarth • Terrain • Telemetry • Cryptography • LIDAR • Embedded • Mobile • iPhone/iPad/iOS • Android
@alphapixel facebook.com/alphapixel (775) 623-PIXL [7495]

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