Surface plot/3d phase diagram

GH geniuses,

Once again my forehead is banging its way through the proverbial brick wall of having-looked-at-this-for-far-too-long-and-can’t-figure-it-out-on-my-own. Please help.

I’m trying to create a (3d) surface plot that combines values from a number of (2d) graphs. I’d like the logic to follow that of a phase diagram (What is a 3D phase diagram? + Example).

It’s a messy and partly redundant definition (sorry) as I’ve been playing with things back and forth, but I’ve sketched an axis system and drawn some funky (too funky) curves (cheers Daniel Christev!) that are rotated onto the (zx) and (zy) planes in a sort-of-similar fashion to the attached image of a phase diagram.

Each value along the red graph A corresponds to a value along the red graph C; each value on the blue graph B corresponds to a value on the blue graph D. But how do I plot each (xyz) surface of those values, ie how do I get my grey points to form the “correct” surface - and how do I merge those two surface into one?

Let’s say we’re designing a spaceship. The red and blue graphs are two materials we might use. The x, y, and z axes are material cost, weight, and volume, respectively (so here’s where those funky curves clearly don’t make sense, but let’s not get hung up on that). The (zx) graphs show the volume-to-cost ratio for the red and blue materials. The (zy) graphs show their volume-to-weight ratio. Looking at the diagram in top view would yield a third diagram, plotting cost against weight.

I’m struggling both with the logic that produces the final (combined) surface(s), and with the maths part.

Any takers?

Many thanks,

pvt_phase_diagram_med 190814_first (33.0 KB)

I don’t think you can solve this unless you have the “iso-curves” mentionied at 6:30 in that video.

If you have them then on this picture above place them at the specific T1, T2, T3… points.


The phase diagram plots three inter-related attributes of one item. From your description, you want to plot three attributes each of two items. You make no mention of a relationship between the two materials that would cause an interaction between their attributes. Thus, you can draw two separate graphs.

If you want to show an interaction between the materials, you need to lose an attribute or add a fourth dimension…

Now go stick a band-aid on your forehead. :stuck_out_tongue_winking_eye:

1 Like

Thanks Ivelin and Jeremy,

Good points, both of you. I have the luxury of being able to pick attributes pretty much at whim, possibly so as to form the relationship mentioned by Jeremy. I realise I have to start by drawing one graph at a time, and keeping one attribute constant as I hunt down those “isotherms” (or iso-whatever, really).

I’ll let you know if I manage to push this further.


I need to do something like this:

Did you find any pertinent solutions to your diagrams?

Hello Lauge,

Very sorry for not getting back to you sooner. Had to put this project to the side for a while and sort of dropped out of the discussion, but will get back to it in the next few weeks. Are you still interested in modelling phase diagrams? I got pretty close I think, though some finishing touches are certainly (long over)due.

Let me know if you’re still working on this, I’ll check in more often from now on.


Hi Magnus,
No worries, there was a little political scandal obscuring my life and I have had to get adjusted to our new dystopian overlords.
I would love to see what you have brewed up.