Author Topic: Curviness of arrows  (Read 200 times)

Offline Ashok

  • Newbie
  • *
  • Posts: 1
Curviness of arrows
« on: November 28, 2018, 03:01 AM »
Hi
I have been using e-sankey for a few years now and its a great tool for my work !!

Some suggestions to improve ease of producing a sankey:

1. Can we have the arrow head and arrow tail boxes unchecked as default. We can turn it on when required. i have also used online tools for sankey and i think most of the flows arrow doesn't have an arrow head and tail and visually it looks good without head/tail

2. One major difference i could see between this application and an online sankey diagram creators is that the look and feel is better than this one. The style and graceful look of the curviness of arrows definitely beats this version. Please check sankeymatic.com. The more or less sharp bend of flow lines in esankey could be improved to have much more curviness and the transition from curve to straight and vice versa is not gradual and smooth.

Other than above e!Sankey is my go-to tool for creating sankey diagrams. The tool is almost perfect and i love the customizations and refinements added lately. Please continue your great work :-)

regards
Ashok

Offline pbeilschmidt

  • Administrator
  • Hero Member
  • *****
  • Posts: 538
  • e!Sankey - show the flow.
    • Umberto - know the flow.
Re: Curviness of arrows
« Reply #1 on: November 28, 2018, 10:45 AM »
Hello Ashok,

thanks for your input. It is great to hear that you like e!Sankey.

1. Can we have the arrow head and arrow tail boxes unchecked as default. We can turn it on when required. i have also used online tools for sankey and i think most of the flows arrow doesn't have an arrow head and tail and visually it looks good without head/tail

I guess that you have the typical alluvial diagrams or distribution diagrams in mind (see here), where the nodes are linked by non-directed bands rather than by directed arrows. These bands without visible heads or tails are very popular indeed, in particular when they are used to visualize relationships between categories, rather than flow between nodes.

We have decided to have arrow heads and tails turned on in the default template, because in many other Sankey diagrams (=other than the alluvial or distribution diagrams, which can be considered as sub-set of the Sankey diagrams), people want to show the direction of flow.

It is no problem to have no arrow head and tail by default. Just create a template in your preferred style, and save it as a Sankey template (.santem). Then define your preferred template as default. All Sankey diagrams you create from that moment will have by default arrow head and arrow tail boxes unchecked.

Have a look at the attached alluvial diagram attached to this post. It is one of the templates I use.

2. One major difference i could see between this application and an online sankey diagram creators is that the look and feel is better than this one. The style and graceful look of the curviness of arrows definitely beats this version. Please check sankeymatic.com. The more or less sharp bend of flow lines in esankey could be improved to have much more curviness and the transition from curve to straight and vice versa is not gradual and smooth.

Yes, I agree, these soft curves look very nice. I think the main reason behind this is that the online tools based on d3.js sankey use a drawing alorithm based on Bézier curves, while e!Sankey doesn't. We have discussed the idea of offering Bézier curves as an alternative drawing style, but there are also some downsides to it...

You can get close to the Bézier curve style by reducing the length of the first/last arrow segement (from the node to the yellow arrow point) and setting a higher curviness value in the arrow properties. Both settings are also defined as options, so if you like the arrows rounder and with softer curves, I recommend you set a short arrow segment default and a high curviness default in the options.

The attached Sankey diagram has smoother curves, but yes, these are not arrows based on Bézier curves.

What do the others e!Sankey users think? Should we also implement arrows based on Bézier curves as an alternative drawing style?
« Last Edit: November 28, 2018, 02:31 PM by pbeilschmidt »
Peter Müller-Beilschmidt
e!Sankey Forum Moderator
ifu Hamburg GmbH