[Paraview] Transparency based on scalar

[David Pont]

Hi Tim,
A workaround may be to create your own color map which includes alpha values. In Object Inspector, Display tab, Color panel, Edit Color Map... you can choose from a set of preset color maps, and Import your own. I have used Export on an existing one to save as xml, then edited or written new xml color map, and Imported that although I never played with alpha values.
I have noticed in the interactive Color Scale Editor GUI some color maps allow you to interactively set alpha while at other times they do not ! Perhaps something to do with the type of dataset? In which case you may be stuck? ie volumes allow alpha, surfaces don't? You might even try interactive editing first, by clicking in the color bar in the Color Scale Editor you can add new points, dragging those up or down changes opacity, as does manually entering a value in the Opacity box, but sometimes that is disabled. Someone out there must know the reasons behind this? but perhaps there are enough clues here for you to make something work for you.

  cheers Dave
David Pont
Scientist - Forest Management Science
Scion
49 Sala Street, Private Bag 3020, Rotorua 3046, New Zealand
DDI +64 7 343 5663
www.scionresearch.com<http://www.scionresearch.com/>

[cid:image001.png at 01CBCC24.C93258C0]

From: paraview-bounces at paraview.org [mailto:paraview-bounces at paraview.org] On Behalf Of Moreland, Kenneth
Sent: Sunday, 13 February 2011 7:16 p.m.
To: gtg085x at mail.gatech.edu; paraview at paraview.org
Subject: Re: [Paraview] Transparency based on scalar

If I understand your question, this is not directly supported.  Although in volume rendering you can set opacity based on the scalar value, in surface rendering you cannot.  There is an entry in ParaView UserVoice for this feature.  If you feel ParaView should support this feature, you should go to this UserVoice link and vote for it.  It will help ParaView developers determine which features to next implement.

http://paraview.uservoice.com/forums/11350-general/suggestions/1354583-transparency-opacity-in-surface-color-map?ref=title

It may be possible to have a filter to create a field of colors with alpha value and then render dependent colors.  I know of no existing filters that already do that, though.

-Ken


On 2/11/11 6:48 PM, "Tim Gallagher" <tim.gallagher at gatech.edu> wrote:
Hi,

I would like to set the transparency of something based on a scalar. For example, if I took a Slice of a dataset, I would like to make it transparent based on, say, density gradient such that zero-gradient is transparent and some value indicates opaque.

I haven't seen any existing filters to indicate this is possible. Is there a filter that does it? Is it something that's even possible to do through, say, a programmable filter?

We're just getting into scripting with Paraview and it takes us a long time to figure out how to even do simple things, so before I spin my wheels on this one, I'd like to get some expert opinions on if it's even feasible.

Thanks,

Tim
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