[osg-users] Culling and instanced drawing

[Werner Modenbach]

Hi Robert,

that is exactly what we have done. It is necessary i.e. for the
automatic compution of zNear/zFar.
My problem is the culling - the collection of visible objects.
If I zoom in very close I get a high level of details. But the shaders
have to do this expensive computaion for all instances,
even if only one is visible.
The only solution I see is "removing those instances not visible".
Instancing reduces time for draw traversal significantly!

Thanks

- Werner -

Am 13.07.2018 um 18:51 schrieb Robert Osfield:
> Hi Werner,
>
> The best way to handle the vertex shader moving geometry to new
> locations is to use a custom osg::DrawableComputeBoundingBoxCallback
> that you assign the the drawable that you are using for instancing.
> You'll want to return a BoundingBox that encompasses all the positions
> that the transformed geometries can occupy.
>
> Robert.
> On Fri, 13 Jul 2018 at 17:44, Werner Modenbach
> <Werner.Modenbach at texion.eu> wrote:
>> Hi all,
>>
>> maybe someone has some inspiration for me.
>> I have a scene graph where the same object (plenty of vertices) is drawn
>> in many instances.
>> Each instance gets an offset matrix to move the object to some place.
>> If I do the rendering without instances the culling removes those
>> objects from the draw list that are not visible.
>> Is there any way to implement such culling also with instances?
>> I think I need to remove the invisible matrices from the list and reduce
>> the number of instances somehow.
>>
>> Any idea where to do it?
>>
>> Thanks
>>
>> - Werner -
>>
>>
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