[Paraview-developers] [Paraview] (Ordered) Compositing question.

Mon Nov 19 10:57:09 EST 2012

John,

Look at vtkStructuredGridVolumeRepresentation, It passes a
 "ExtentTranslator" to the view. The view uses the extent translator to
build the KdTree. That's one of specifying the cuts. You can indeed provide
a custom extent translator or if need be, that API can be extended to pass
some other data-structure to extract the relevant information for ordered
compositing.

For using opacity with polygonal data, simply go to the lookup table editor
dialog and (in the advanced mode) you'll see a checkbox to "Enable Opacity
Function". Check that and you can specify the opacity function.

Utkarsh

On Mon, Nov 19, 2012 at 10:49 AM, Biddiscombe, John A. <biddisco at cscs.ch>wrote:

>  Thanks Ken,****
>
> ** **
>
> My suspicions are confirmed. I had a poke around with the ordered
> compositing code (vtkOrderedCompositeDistributor et al) and saw that the
> BSP cuts from the D3 filter are set to match those from the PKDTree
> internally. I notice that in the BSPcuts code it says****
>
>   // Description:****
>
>   //   Initialize the cuts with arrays of information.  This type of****
>
>   //   information would be obtained from a graph partitioning software***
> *
>
>   //   package like Zoltan.****
>
> ** **
>
> Do you know if there exists such an example. I am infact partitioning the
> data using Zoltan and have the exact bounds etc of the partitions, so I can
> work out what to pass into the BSPcuts  class and could potentially fool
> the IceT composiining into using my partitions. Can you point me to any
> crucial function that I must call. Is it sufficient to do a SetCuts on the
> compositing code – which class do I need to take control of?).****
>
> ** **
>
> I shall create a custom representation to handle the depth sort. I’ve done
> the same some time ago for the point sprite renderer so I’ll manage that
> ok, but I’ll need to override the IceT compositing pass too as alluded to
> above , so any pointers welcome. (Could I somehow subclass on of the
> painters for the IceT pass and set the cuts to what I’ve got, then proceed
> as usual?)****
>
> ** **
>
> Thanks****
>
> ** **
>
> JB****
>
> ** **
>
> *From:* Moreland, Kenneth [mailto:kmorel at sandia.gov]
> *Sent:* 19 November 2012 16:13
> *To:* Biddiscombe, John A.
> *Cc:* paraview-developers at paraview.org; paraview at paraview.org
> *Subject:* Re: [Paraview-developers] (Ordered) Compositing question.****
>
> ** **
>
> You are correct in that if you disable ordered composite it will disabled
> the distribution and the composite ordering. The problem is that the
> geometry distribution also creates a k-d tree structure that the
> compositing uses to determine the visibility order. So it would not be
> sufficient to simply have geometry that is in non-overlapping pieces. You
> would also have to provide some meta-structure that could be used to
> determine an appropriate ordering given a viewpoint. Even if you had that,
> there is no mechanism to feed that to the compositor in the view. I can't
> think of any way of doing that that would not be a huge hack.****
>
> ** **
>
> As far as I know, there is no support for the DepthSortPolyData filter.
> You would probably have to create a custom representation to support that.
> ****
>
> ** **
>
> I believe the transparent lookup table for poly data is supported in 3.98,
> but to be honest I have not yet tried it.****
>
> ** **
>
> -Ken****
>
> ** **
>
> Sent from my iPad so blame autocorrect.****
>
>
> On Nov 19, 2012, at 3:46 AM, "Biddiscombe, John A." <biddisco at cscs.ch>
> wrote:****
>
>  I have geometry distributed into parallel pieces such that they are non
> overlapping and therefore compositing should only need to use a back to
> front sort last frame buffer operation with no redistribution of geometry.
> ****
>
>  ****
>
> I’m worried that when I turn on transparency, paraview will try to
> redistribute my data, even though I have already partitioned it nicely for
> this. I’d like to use ordered sort last compositing at the top level, and
> use DepthSortPolyData on each node (no depth peeling for now) to ensure I
> get a true image. What isn’t clear to me is if I “disable ordered
> compositing” if this disables the transfer of geometry AND also disables
> the ordered compositing necessary for correct transparent blending (I may
> be confused here about the blend modes used or the term “ordered
> compositing” as used in the docs).****
>
>  ****
>
> Is there written down anywhere a complete description of the pipelines
> used by the various rendering modes so that I can be sure the pipeline is
> doing what I want. I can create a custom representation which does what I
> want, but it’ll take time and if the existing mechanism support it, I
> shouldn’t need to.****
>
>  ****
>
> Also, I specifically want to use a transparent lookuptable, does the newer
> paraview 3.98 have anything to support this. I thought I’d seen a thread
> about this recently, but cannot find it now.****
>
>  ****
>
> In summary : For the rendering, I’d like Ordered sort-last compositing, no
> geometry redistribution, Depth sort of polygons on each node. Transparent
> lookup table.****
>
>  ****
>
> What settings should I use J****
>
>  ****
>
> Thanks****
>
>  ****
>
> JB****
>
>  ****
>
> -- ****
>
> John Biddiscombe,                        email:biddisco @.at.@ cscs.ch****
>
> http://www.cscs.ch/****
>
> CSCS, Swiss National Supercomputing Centre  | Tel:  +41 (91) 610.82.07****
>
> Via Trevano 131, 6900 Lugano, Switzerland   | Fax:  +41 (91) 610.82.82****
>
>  ****
>
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