[Paraview-developers] (Ordered) Compositing question.

[Biddiscombe, John A.]

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<mailto: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 :)

Thanks

JB

--
John Biddiscombe,                        email:biddisco @.at.@ cscs.ch<http://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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