[Paraview-developers] Color Scale Editor Design

[Biddiscombe, John A.]

One of the features I have an intern working on - and I need, is the ability to use Gradient Opacity for volume rendering. I had a plugin which enabled this, using a 2D transfer function editor (stolen from visit again, like the point sprite stuff, but I ended up having to rewrite most of it)

Could you please make it easy for me to hook this kind of feature into the standard colour editor? rather than having to redo it all in the plugin.

None of it compiles at all right now as it was last used in 2010 and the server manager and everything has been completely changed. I asked about this on the list a week or so ago, but now I see from looking at the code that the vol-render plugin I made is obsolete as the one in paraview does camera aligned slices etc, All I need to do is expose the gradient opacity features and hook my editor into them. (It does histograms and stuff too inside the editor, but probably there's a vtk2DTransferFunction Widget somewhere we could use instead).

Etc etc, just thinking out loud.

JB

> -----Original Message-----
> From: paraview-developers-bounces at paraview.org [mailto:paraview-
> developers-bounces at paraview.org] On Behalf Of Utkarsh Ayachit
> Sent: 10 July 2013 20:24
> To: burlen
> Cc: ParaView Developers
> Subject: Re: [Paraview-developers] Color Scale Editor Design
> 
> Burlen,
> 
> > 1) combine the opacity widget and the color scale widget.
> 
> Good idea! Let me see how much effort that's going to be. Hopefully, it's not
> too bad to add support for this.
> 
> > I think it would also be very useful to display a histogram of the active scalar
> plotted using the LUT colors in the new widget.
> 
> We have thought of this in the past. As useful that this is, it's a bit tedious to
> implement. I'll put that as a feature request to be addressed in future for
> now.
> 
> > 2) add a "mirror scale" option.
> 
> Should be too hard to add.
> 
> 
> > Also, with the current color scale widget it's pretty difficult to interactively
> manipulate LUT's with many color points (eg when 256 colors are explicitly
> specified). The control points are too close together to select and they way
> it's implemented now you'd need to move surrounding control points as
> well.
> 
> Burlen, for such cases you may want to look into using the newly added
> "categorical color" support rather than adding 256 control points.
> 
> 
> > 3) limit the number of control points used by the widget. The default max
> number of control points used by the widget would be something
> reasonable like 16 but the user could increase if desired via a qt spin control.
> The active control points in the widget would be evenly spaced across the
> scale and during interaction as the user moves the visible control points the
> widget would handle linearly re-interpolating the position of the hidden
> control points automatically.
> 
> I'm not sure I follow the need for this. With support for categorical colors,
> some of the use-cases with large number of control points may become
> unnecessary.
> 
> Utkarsh
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