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I need an illustration of a translucent ellipsoid so that I can also see a vector form the origin to an offset center and a vector from that point to somewhere on the surface of the ellipsoid. Something like the lovely old illustrations in Halliday and Resnick would be great but I have no artistic talent.

I have tried the usual Open Source and web based applications, including the Wikipedia recommendations on how to make illustrations for Wikipedia, and can't find a way to get what I would call textbook or tutorial quality figures that clearly illustrate what I can clumsily draw.

The old potato surface and Gauss's Law in Arfken or the stereo pairs in Morse and Feshbach are heads and shoulders above anything I have been able to get from Mathematica's online tools, or Geogebra, or other StackExhange answers etc.

Here is an illustration from Simon's Mechanics that has some of the features. It has a translucent surface and vectors and notation are visible inside. enter image description here

The case I need to draw will show 3 axis, an offset vector from the origin and a vector from the offset to a point on the surface. (It would be a sphere centered on the origin if ideal. There are three offset errors and 3 gain errors).

This may not qualify as a physics question unless I ask for the path the pencil will take to get a projection of the object onto a page. If there is a good list of apps or examples or an answer I have missed, much appreciated.

Qmechanic
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C. Towne Springer
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  • Can you link to an image of the kind that you would like to make? – CuriousOne Feb 08 '16 at 05:13
  • I am, too, unsure about what exactly you need, but I would prefer using error bars of any kind instead of a translucent ellipsoid. As a matter of fact, the latter always projects to an ellipse, making it harder to interpret in 3D. – dominecf Feb 08 '16 at 10:06
  • @CuriousOne I added an example. I hope to draw the figure I need with software and vary the errors I am demonstrating in order to exaggerate them and make them obvious. – C. Towne Springer Feb 09 '16 at 08:46
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    I'm voting to close this question as off-topic because it's about computer software for making duagrams – innisfree Feb 09 '16 at 08:52
  • I see... that's getting complicated. Personally I would try one of two things: 1) Use of a 3d renderer or shader like Povray... the results might be underwhelming because the idea of 3d objects often sounds better than the actual 3d objects look, especially when translucency comes into play and the human visual system gets overwhelmed. 2) Write an algorithm (I would do it in Python) to generate an SVG file. The latter has the advantage that you will also understand the math of this object in detail. – CuriousOne Feb 09 '16 at 08:52
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  • I second the motion to close the question 2. If you just want illustrate a concept without needing special values, do it by hand ! You will waste so much time if you try to find a good way to come up with a "correct" solution (i.e. one gathered from a projection of 3d objects). I would suggest inkscape.
    • – Bort Feb 09 '16 at 09:03
  • @CuriousOne I have made some attempts in PyQt and iPython Notebook. I guess there is a good reason I had a hard time finding an example and scanned a book from 40 years ago. I don't think I need Pixar to do this for me but must be plenty of people in engineering and science who need to to do this kind of thing with precision. Someone better at writing PostScript than I can do it. A pencil rendering by an artist will be quicker. Maybe doing it in layers -- I'll have to project the ellipse and fake the shading. Not satisfactory. – C. Towne Springer Feb 09 '16 at 09:08
  • @innisfree Regarding discussion of software to make diagrams to use on Physics Stack Exchange. Is there a meta-list or topic? Or just don't ask don't tell? – C. Towne Springer Feb 09 '16 at 09:09
  • @Bort I would do that if I had hands that worked. – C. Towne Springer Feb 09 '16 at 09:13
  • I have never encountered this problem in my entire career, neither do I find this kind of illustration useful. Projective 3d objects are not very good at conveying quantitative information because humans can't "unproject" them with any precision. I would agree with some of the other comments that you are wasting your time on something that is not nearly as enlightening as you may think it is. Maybe you should post a different question about the problem you are actually trying to solve? – CuriousOne Feb 09 '16 at 09:19
  • @CuriousOne You may be right about wasting time. As for the usefulness, when I place the object in the center - something with inertial navigation - and show what it thinks its instantaneous state is compared to its true position I think it will be clear. If your career involved methods of intercepting ICBMs or hyper-velocity munitions you may have looked for ways to explain to the engineering and software people involved. This will "put them in the seat" which in the past has been effective. It should also work for showing the errors in a simple 3-axis accelerometer. – C. Towne Springer Feb 09 '16 at 09:31
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    @C.TowneSpringer I am really not that talented at arts, but this also not that difficult of a drawing.. heres a rough sketch (inkscape.. maybe 10 minutes) https://imgur.com/tYxDLWw . The most important advice I would give you: always do a fake lighting / shadowing. Doesnt need to be good, but still really helps the image – Bort Feb 09 '16 at 09:41
  • While I haven't been shooting ICBM's, I have seen aeronautical and space navigation displays and I do not remember seeing information displayed this way. Could you link me to such an illustration, please? @Bort: That looks really nice. I agree... fake shading is usually better than the real thing. – CuriousOne Feb 09 '16 at 09:43
  • @Bort That is pretty nice. I'll need to do it with some sort of rendering/plotting software to get the points where the axis emerge correct. I'm looking for general tools. In this one case The ellipsoid is aligned with something like an airplane with X, Y, Z being roll pitch and yaw but it could as easily be like the text illustration above, the polhode describing the herpolhode as it rolls on the invariable plane in rigid body rotation, not that I have ever seen that one outside all the older mechanics books. – C. Towne Springer Feb 09 '16 at 10:00