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Understanding osg::CulingSet::pixelSize() and computePixelSizeVector()


 
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白杨
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PostPosted: Mon Jul 31, 2017 8:27 am    Post subject:
Understanding osg::CulingSet::pixelSize() and computePixelSizeVector()
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Hi Folks,

I am tring to understand a parameter in the function
osg::CullintSet::pixelSize, _pixelSizeVector. It is computed by the function
osg::CullingSet:: computePixelSizeVector(W, P, M). Could you please explain what mathematical methods it is according to?
And especially, what these parameters following are meaning, P00, P20_00, scale_00, P23, P33?


Thanks a lot.

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robertosfield
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Joined: 18 Mar 2009
Posts: 11021

PostPosted: Mon Jul 31, 2017 8:52 am    Post subject:
Understanding osg::CulingSet::pixelSize() and computePixelSizeVector()
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Hi (could you sign with the name you'd like to be addressed as, it helps with flow of threads and threads friendlier.)


I wrote the pixelSize code well over a decade ago and worked out the maths myself, the aim was speed of operation rather than accuracy, so it's an approximation of pixel size when transforming into screen space.  The derivation was all done on paper which I will have discarded once I had implemented the functionality - the code remains as the formal specification of the maths.


As it's so long since I wrote the code or even looked at (it's been working reliably for over a decade:-)  so I'd need to sit down and work exactly what each variable does, personally I don't have time for this as I have lots of other work to do.



Robert.


On 31 July 2017 at 09:26, 白杨 < (
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Quote:
Hi Folks,

I am tring to understand a parameter in the function
osg::CullintSet::pixelSize, _pixelSizeVector. It is computed by the function
osg::CullingSet:: computePixelSizeVector(W, P, M). Could you please explain what mathematical methods it is according to?
And especially, what these parameters following are meaning, P00, P20_00, scale_00, P23, P33?


Thanks a lot.







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