[osg-users] Understanding osg::CulingSet::pixelSize() and computePixelSizeVector()

[Robert Osfield]

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 <337533078 at qq.com> wrote:

> 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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