[vtkusers] Large number of actors

[Arnaud GELAS]

On 06/09/2011 02:59 PM, Nicolas Rannou wrote:
> Hi Clint,
>
> Thanks for the clarification about vtkMultiBlockDataset.
>
> We need multiple actors so we will have to find another solution....
>
> "Caching" might be an option.
> If we are at the time point N, we would keep in memory the actors from time point N-1, N and N+1 and update the 3 vectors(?) when we move through the time.

What about using a ring buffer?

> Has VTK such capabilities or would somebody have any recommendation about the best practice to adopt?
>
> Thanks
>
> Nicolas
>
> On Jun 9, 2011, at 1:29 PM, Clinton Stimpson wrote:
>
>> On Wednesday, June 08, 2011 03:48:38 pm Nicolas Rannou wrote:
>>> Hi Clinton,
>>>
>>> I've been reading about the vtkMultiBlockDataset but I am not quite sure
>>> about how it could improve the performance.
>> Its an alternative similar to
>> vtkPolyData->vtkStripper->vtkAppend->vtkMapper->vtkActor
>>
>> vtkPolyData->
>> vtkPolyData->   vtkMultiBlockDataSet ->  vtkCompositePolyDataMapper2 ->  vtkActor
>> vtkPolyData->
>> ...
>>
>> The difference is you don't do a vtkAppend which duplicates the data and
>> increases your memory usage.
>>
>>>  From my understanding, it would store/order the polydatas in a tree
>>> structure. But the main issue are the actors and mappers... (not the
>>> polydata itself...) After storing my polydatas within
>>> vtkMultiBlockDataset, I still have to generate N actors from my N
>>> polydatas which belong to my block of interest...
>>>
>>> I tried to create 1 block per polydata.
>>>
>>> 1-add polydatas in the multi block dataset using
>>> vtkMultiBlockDataset::AddBlock()
>>> 2-extract/append polydatas
>>> vtkCompositeDataGeometryFilter or vtkMultiBlockDataset ::GetBlock()
>>> 3-map it and visualize it through 1 actor and one mapper.
>>>
>>> vtkCompositeDataGeometryFilter generates 1 polydata from all polydatas,
>>> which makes picking impossible... vtkMultiBlockDataset ::GetBlock() will
>>> return 1 polydata, which will not improve the performance since we have to
>>> create 1 mapper and 1 actor for each polydata present in this block.
>>>
>>> Is there a better practice to render all polydatas which belong to a block
>>> through multiple actors. Am I missing something?
>> If you're going to use multiple actors, then don't use a vtkMultiBlockDataSet.
>>
>> If you really want multiple actors, you could look at vtkMapper::SetStatic to
>> speed up the multiple actors/mappers.
>> But then you'll have to do extra work if pipeline changes need to be accounted
>> for.
>>
>> Clint
>>
>>> Thanks
>>>
>>> On Jun 8, 2011, at 3:11 PM, Clinton Stimpson wrote:
>>>> On Wednesday, June 08, 2011 01:00:48 pm Nicolas Rannou wrote:
>>>>> Hi all,
>>>>>
>>>>> Our application requires to render up to 5000x1000 PolyDatas.
>>>>> Each polydata is made of 500 triangles.
>>>>>
>>>>> It looks like it is impossible to store all the related actors in memory
>>>>> (on a machine with 48Gb RAM).
>>>>>
>>>>> We have been playing around with things such as "vtkStripper",
>>>>> "ImmediateRendering", "ReleaseDataFlag", "BackFaceCulling", etc.
>>>>>
>>>>> For 1000 PolyDatas:
>>>>>
>>>>> The best option in term of memory looks like turning
>>>>> "ImmediateRendering" ON. ->  1000 actors
>>>>>
>>>>> 	->  60 Mb of memory usage
>>>>> 	->  slow interaction
>>>>>
>>>>> The best option in term of interaction seems to be using the following
>>>>> pipeline: vtkPolyData->vtkStripper->vtkAppend->vtkMapper->vtkActor
>>>>>
>>>>> 	->1 actor
>>>>> 	->  90mo in memory
>>>>> 	->  good interaction
>>>>>
>>>>> Using only one actor is not an option for us since we want to be able to
>>>>> pick and change properties of each object (individually).
>>>>>
>>>>> Would somebody have any advise?
>>>> In this situation, I think you can get both interaction speed and memory
>>>> savings by putting your many vtkPolyData objects into a
>>>> vtkMultiBlockDataSet and rendering that with an actor or a few actors.
>>>>
>>>> You could put some properties, such as colors, in the vtkPolyData instead
>>>> of the vtkActor.  And for other properties, you could use the same
>>>> actor/mapper for those objects that share the properties.  Or perhaps
>>>> use vtkPainter to customize rendering of these objects.
>> -- 
>> Clinton Stimpson
>> Elemental Technologies, Inc
>> Computational Simulation Software, LLC
>> www.csimsoft.com
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