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

[Alex Taylor]

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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