[Paraview-developers] [EXTERNAL] Re: Color Scale Editor Design

[Scott, W Alan]

Utkarsh,
I went through your proposed mockup, and really like it.  I also agree with 1) and 2) from Burlen below, and agree with your thoughts on 3) below.  

As a side thought, we already have the color widget and opacity widget combined when in volume rendering mode.  Just re-use that.  It is a wonderfully powerful tool.

Be sure to test with Volume Rendering - if that gets broken, ParaView will be unusable for numerous of my users.

I assume that your reply to 2) below has a typo - mirror scale "Should NOT be too hard to add"?  I would also really like this functionality added.  By the way, this is in VisIt, called Invert Colormap.  Also, this is bug/ feature request 13651.

A piece of functionality that would be really nice to have is the ability to set the colors outside of the min-max range to something.  For instance, if a cell has an EQPS above a certain max number, set it to pink, or white.  Basically, make it stand out, showing that it is outside of the range.  Bug number 6657.

The only other thing I can think of would be to allow a user to change the log base.  That way, you could get "log" type scaling even though you didn't have a large range.  Not sure if I explained what I mean correctly, ask if I am not making sense.

Here are the bugs I could find related to the color editor.  Not trying to overwhelm, but if we can get bugs fixed easily or for free, I figure it is a cheap win!

Bug 13546 would be nice to have (not sure it is related to current work, but should be really easy.)
Bug 13130 would be nice to have (not sure it is related to current work, but should be really easy.)
Bug 12975 would be nice to have (assuming it is reasonably easy.)
Bug 13776 should be resolved by your current work.
Bug 12899 would be nice to have (not sure it is related to current work)
Bug 11858 would be nice to have (not sure it is related to current work)
Bug 8877 would be nice to have (change two clicks to one, when a user wants to manually set color range.)
Bug 8878 would be nice to have (Allow volume rendered color/opacity widget to be edited before volume rendering.)

Thanks,

Alan


-----Original Message-----
From: Utkarsh Ayachit [mailto:utkarsh.ayachit at kitware.com] 
Sent: Wednesday, July 10, 2013 12:24 PM
To: burlen
Cc: ParaView Developers; Scott, W Alan
Subject: [EXTERNAL] 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