[osg-users] Changes in osgVolume from 3.0 to 3.4

[Robert Osfield]

Hi Alex,

There were quite a few improvements to osgVolume between OSG-3.0 and
OSG-3.4, both in shaders and the introduction of the new
MultiPassTechnique.  One thing to look at with your own setup is that you
aren't picking up on old
 shaders such as by having your own path to old shaders.

It's quite a while since I did the work on osgVolume, around two years, so
won't be able to be specific without viewing code and being able to
reproduce the problems you are seeing first hand.

Robert.

On 28 January 2016 at 15:25, Alex Taylor <alextaylor at gmail.com> wrote:

> Hi,
>
> I'm working on upgrading the OSG version used in the product I work on.
> When OSG is upgraded with the same client code, I'm noticing differences is
> the way my volumes are rendered with all of the rendering algorithms that I
> can't explain. I've fixed the parameters I'm using to define the osgVolume
> in both versions, so it can't be a matter of picking up a different default
> option for a parameter.
>
> *OSG 3.4 Fixed Function*
> [image: osg34RayTraced.jpg]
> *OSG 3.0 Fixed Function*
>
> *[image: osg30FixedFunction.jpg]*
>
> *OSG 3.4 Ray Traced Lit*
>
>
> *[image: osg34RayTracedLit.jpg]*
> *OSG 3.0 Ray Traced Lit*
>
>
> *[image: osg30RayTracedLit.jpg]*
>
> *OSG 3.4 Isosurface*
>
> *[image: osg34Isosurface.jpg]*
> *OSG 3.0 Isosurface*
>
> *[image: osg30Isosurface.jpg]*
>
> In the Ray Traced cases, I'm using the properties:
>
> AlphaFunc = 0.02;
> SampleDensity = 0.005;
>
> I'm using setting the TransferFunctionProperty, so I'm using the shaders
> to do the alpha/color mapping.
>
> For the FixedFunctionTechnique, I'm using AlphaFunc = 0.02, and using
> the applyTransferFunction function to obtain an RGBA mapped osg::Image
> buffer.
>
> It's very possible that the upgrade to 3.4 has changed something else in
> my overall use of OSG elsewhere in the pipeline, unrelated to osgVolume,
> that is causing this issue. That said, I thought i'd ask if visually anyone
> has a guess it what might have changed between osg 3.0 and osg 3.4 that
> might explain these visual differences.
>
> Thanks for your help,
>
> Alex
>
>
>
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>
>
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