[osg-users] Viewing Stacked Semi-Transparent Geodes

[Christian Buchner]

There are techniques to perform order independent transparent rendering,
one of these is demonstrated in the osgoit example
of OpenSceneGraph. However osgoit uses a multipass technique and can be
rather slow.

Christian


2016-02-04 9:31 GMT+01:00 Voerman, L. <l.voerman at rug.nl>:

> Hi Erik,
> the effect you see is caused by your blend function being order dependent,
> for a good result transparent triangles need to be drawn back to front.
> Did you set the rendering_hint to TRANSPARENT_BIN (binNumber 10 / binName
> DepthSortedBin)?
> like in stateSet->setRenderingHint(StateSet::TRANSPARENT_BIN);
> Regards, Laurens.
>
> On Wed, Feb 3, 2016 at 9:48 PM, Erik Hensens <ehensens at hunter.com> wrote:
>
>> Hi everybody!
>>
>> I have two geodes, each is a flat circular disk with some circular holes
>> removed. Each geode is flat in the YZ plane, and they are stacked against
>> each other with a small amount of spacing, centered at (x1, 0, 0) and (x2,
>> 0, 0). There is a single parent matrix transform node that is the parent of
>> both of these geodes, and I use the matrix transform to set different
>> rotations. Each of these disk geodes is semi-transparent by means of
>> calling setAlpha on their materials for the FRONT_AND_BACK faces.
>>
>> The problem is that at certain parent matrix transform rotations certain
>> parts of the first disk are more visually prevalent and at other rotations
>> certain parts of the second disk are more visually prevalent, i.e. how
>> these two semi-transparent geodes are viewed against each other changes
>> based on the rotation of the parent matrix transform. I've attached two
>> images to show you the difference.
>>
>> What is causing this effect and how can I eliminate it? I want it to look
>> the same no matter what the rotation of the parent matrix transform is.
>>
>> Thanks in advance for any help!
>>
>> Cheers,
>> Erik
>>
>> ------------------
>> Read this topic online here:
>> http://forum.openscenegraph.org/viewtopic.php?p=66186#66186
>>
>>
>>
>>
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>>
>>
>
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