[osg-users] 回复: Understanding osg::CulingSet::pixelSize() andcomputePixelSizeVector()

Young 337533078 at qq.com
Mon Jul 31 02:19:23 PDT 2017

Hi Robert

Is _pixelSizeVector  meaning the ratio of space distance to screen pixel?

Thanks for your reply.
------------------ 原始邮件 ------------------
发件人: "Robert Osfield";<robert.osfield at gmail.com>;
发送时间: 2017年7月31日(星期一) 下午4:51
收件人: "OpenSceneGraph Users"<osg-users at lists.openscenegraph.org>; 

主题: Re: [osg-users] Understanding osg::CulingSet::pixelSize() andcomputePixelSizeVector()

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.


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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