[osg-users] osgvolume multipass (hybrid geometric/volumic) bug...?

Robert Osfield robert.osfield at gmail.com
Mon Mar 6 01:21:54 PST 2017

Hi Julian,

I have just had a bash at recreating issues and have found a volume
model that works in close enough dimensional space to the cessna.osg
that I start seeing problems with the rendering of the volume
occluding the cessna at times when it shouldn't and at certain angles
the parts of the cessna appear in the wrong part of the volume cube.

I haven't seen this issue before so at this stage can't provide any
suggestions as to what might be wrong.  I will need to investigate,
but this will need to wait as I'm currently doing a major rewrite of
osgText to resolve issues with how it handles VAO's.


On 5 March 2017 at 17:04, Julien Valentin <julienvalentin51 at gmail.com> wrote:
> Hi Robert et al
> It's been a while I use a customized osgVolume::MultipassTechnique and experienced a bug I think was coming from my code but in fact it affect osgvolume application too.
> It seams there a bug in texgen (or somerhing like that) when writing back Pre rendered scene FB  to the main FB..
> It lead to artifact such as
> 1)models out of volume tend to disappears (experienced in osgvolume ex)
> 2)In my own code it cause all sort of strange artifacts
> to reproduce
> Code:
> osgvolume image --multipass --model cessna.osg
> I would like to debug but would like to be sure how it work,
> I tend to understand the following, stop me if I'm wrong:
> 1/VolumeScene children (except tiles) is rendered as in depth and color textures
> 2/Frontface then backface Hull are rendered to determine per pixels ray lengths and then per pixel numiterations ( so rays can be casted in BFHull pass)
> It's been a while I haven't dive in there. Can you tellme if I'm wrong and give me directions of what could possibly go wrong in the current MultipassTechnique...
> Thank you!
> Cheers,
> Julien
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=70407#70407
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