[osg-users] bounding box of culled geometry

[OpenSceneGraph Users]

Hi Renzo,

You may look at osgShadow\MinimalCullBoundsShadowMap.cpp. It scans
RenderBins and compute bounds of culled drawables to optimize shadow map
resolution.

Cheers,
Wojtek Lewandowski

czw., 15 paź 2020 o 12:40 OpenSceneGraph Users <
osg-users at lists.openscenegraph.org> napisał(a):

>
> Hi Werner,
>
> I do not know if I have found the code that you are suggesting. I see that
> CullVisitor could help to find the near and far plane, however with Z I
> meant the world vertical axis, not the axis of the view frustum.
>
> Regards,
> Renzo
>
> On 15-Oct-20 11:25 AM, OpenSceneGraph Users wrote:
>
> Hi Renzo,
> Maybe a node visitor with z-near and z-far as parameter is a possible
> approach.
> Werner
>
>
> On 15. Oktober 2020 09:46:57 MESZ, OpenSceneGraph Users
> <osg-users at lists.openscenegraph.org> <osg-users at lists.openscenegraph.org>
> wrote:
>>
>>
>> Hi Robert,
>>
>> On 14-Oct-20 3:56 PM, OpenSceneGraph Users wrote:
>>
>> Hi Renzo,
>>
>> On Wed, 14 Oct 2020 at 12:00, OpenSceneGraph Users <
>> osg-users at lists.openscenegraph.org> wrote:
>>
>>> I am using osg::Drawable::getBoundingBox() to retrieve the bounding box
>>> around the whole geometry. Is there a similar short way to get the
>>> equivalent box for just the culled geometry or do I need to write my own
>>> procedure?
>>>
>>
>> Culling isn't related to the nodes directly, but to a traversersal of the
>> scene graph that compares the bounding shere's of internal nodes of the
>> scene graph and the bounding boxes of the drawable leaves.  Culling can
>> happen at any point in the hierarchy - it can cull right up at the top node
>> in the scene graph if the scene is outside the view frustum.
>>
>> Within the cull traversal there is no tracking of culled or non culling
>> bounding boxes, a cull test is done and the bool result used directly.
>> There isn't a "bounding box" or "bounding sphere" for culled or non culled
>> objects.  All the cull traversal cares about is building a list of
>> drawables leaves that pass the view frustum test, there is no tracking of
>> any objects that are culled - this would be a crazy waste of CPU resources.
>>
>> I have to ask, why do you want a bounding box of culled objects - what is
>> the high level problem you are trying to solve?  It may well be that you
>> are asking the wrong question thinking about the task you have in the wrong
>> way.
>>
>> Robert.
>>
>>
>> thanks for pointing out how cull traversal operates.
>>
>> Yes, it might be I am searching in the wrong direction. I need to get the
>> minimum and the maximum Z coordinate of the geometry vertices in order to
>> apply a color range. This is quite easy to do for the whole geometry but I
>> would know if there is a way just for the vertices inside the view frustum.
>>
>> Regards,
>> Renzo
>>
>> ------------------------------
>>
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>>
>>
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