Psychrometric chart Mollier hx

AlbertPressler · May 11, 2022, 2:05pm

Hi there!
I just realized that there’s seemingly no option in the psychrometric chart component to switch to Mollier-hx view like in the legacy component.
Am I missing something? Or will that feature be revived?
Thanks!

chris · May 12, 2022, 6:34pm

Hi @AlbertPressler ,

You’re the first one to ask for this. It would have been a lot of work to implement this capability natively in the core code given all of the other options that were added to the chart (eg. The ability to adjust the lower and upper temperature boundaries).

But, if it’s a big pain point, then it shouldn’t be that much work to just mirror the chart and re-position the text. You can do this either with native Grasshopper components or a few lines of GHpython that post-process the chart object coming out of the component.

Right now, while you’re the only one who has asked for this, I’m not planning to add anything to the Grasshopper plugin for it. But, if you want a take a first pass at putting together this post-processing component, I can help you to get it to work. Or I can at least show you the ladybug_geometry Python methods that you can use to mirror the chart.

AlbertPressler · May 12, 2022, 6:49pm

Hey @chris ,
ok thanks… I’ll definitely try putting something together to get the chart right for us Europeans
I’m going on vacation tomorrow, so it probably won’t happen in the next 2 to 3 weeks but I would appreciate some tipps regarding the Python methods
Cheers

chris · May 12, 2022, 6:58pm

Sounds like a plan!

You can start by making a component that mirrors the psych chart polylines and mesh. Essentially, you’ll take the psych_chart output of the current component and you’ll use it to get the ladybug_geometry meshes and polylines similar to what you see here in the component source code:

github.com

ladybug-tools/ladybug-grasshopper/blob/master/ladybug_grasshopper/src/LB Psychrometric Chart.py#L165-L168

    
      
          title_i = [from_polyline2d(psy_chart.chart_border, z)]
          temp_lines_i = [from_linesegment2d(tl, z) for tl in psy_chart.temperature_lines]
          rh_lines_i = [from_polyline2d(rhl, z) for rhl in psy_chart.rh_lines]
          hr_lines_i = [from_linesegment2d(hrl, z) for hrl in psy_chart.hr_lines]

However, before you pass them to those ladybug_rhino functions that convert the Ladybug geometry into Rhino geometry, you’ll call the reflect() method on the meshes and polylines in order to mirror them over a plane. You can see the method here for the mesh object in the ladybug_geometry docs:

https://www.ladybug.tools/ladybug-geometry/docs/ladybug_geometry.geometry2d.mesh.html#ladybug_geometry.geometry2d.mesh.Mesh2D.reflect

Then you just translated the reflected Ladybug geometry to Rhino geometry and output it from the component.

furtonb · December 20, 2022, 8:50pm

@AlbertPressler did you make any progress on this issue?

I also find the Mollier diagram more familiar (the h-x diagram being the go-to representation in my country, referenced in all available handbooks and used by HVAC engineers).

AlbertPressler · December 28, 2022, 7:22am

Hey @furtonb,

Sorry but i haven‘t had the time yet to work on it. Didn‘t really have to use it in the last few months so it was not one of my top priorities.
If I‘m able to work on it I‘ll post the results here of course.