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Discussion - Motion Envelope Improvement Ideas


Discussion - Motion Envelope Improvement Ideas

I've been working with motion envelopes a lot over the last several years.  This is an incredibly useful tool and my organization creates and uses them frequently.  However, they're difficult to create, difficult to use, and difficult to update.  It's time PTC gave this tool an overhaul with the end-users in mind.


The list below are my ideas for improvements.  I intend to post this to the Creo Community Ideas subforum, but first I'm hoping to hear from the community to discuss what I have so far, maybe crowdsource a few more ideas, and hopefully drum up some votes for the Idea post when that happens.  And please feel free to point out spelling/grammar mistakes and ask for clarification on any point.


I'll post this list and any additions to the Ideas subforum in a week or two, depending on how active the discussion here is.


  1. Ribbon toolbar
    • Replace the pop-up dialogue box with a ribbon based menu.
    • Separate this from the Playback tool.
    • This is where I should be able to select mirror planes, body options, frame of reference options, output options, etc.
  2. More envelope output options
    • Option to export a separate mirror part instead of, or in addition to, the regular envelope part.
    • Option to add a mirrored envelope to the same body as the regular envelope or add it to a separate body.
    • An ability to select the mirror plane.
    • Option to export and assemble the envelope to the mechanism assembly it came from.
      • Option to update an existing envelope if it was associated to the mechanism model in this way.
    • Aligned output options between MDX's envelope tool and BMX's Motion Analysis tool.
      • BMX's Motion Analysis tool has the ability to create an envelope feature directly in the feature tree of the mechanism it was generated from.
      • MDX's envelope tool can't do this. It only exports to the startup folder.
      • Both tools should have the same output capabilities.
  3. Change the frame of reference
    • Add an ability to change what reference frame (coordinate system) the envelope uses.
    • Currently, the top level coordinate system, or the ground, of the assembly is used. There's no option to change it.
    • I want to be able to change the coordinate system/reference frame used and have the resulting envelope represent the motion of parts with respect to it, not the ground.
    • This is similar in concept to a "paper part" in the Trace Curve tool where the paper part serves as the frame of reference for the motion.
    • I know of at least two Pro/Workarounds© to do this, but they're labor intensive and I don't want to have to use them. I want Creo to do this for me.
    • See this post from 2010 (@PAULKORENKIEWIC):
  4. Add a smoothing function
    • All envelopes have jittery facets that shouldn't be there.
    • Even flat surfaces have raised and recessed facets.  And because of how Creo merges coincident surfaces into a single surface, this seems to be a cause of export failures.
    • An optional smoothing operation should be added to the envelope tool. The user should be able to turn this option on or off with the understanding that smoothing adds computation time.
    • Sharp edges should be preserved.
    • OR just make the envelope tool better at generating smoother, less jittery surfaces without an added function.
    • See my post here:
  5. Add an option to update existing motion envelopes
    • Currently, envelopes are stand-alone objects with no connection to the mechanism model they were generated from.
    • Methods for updating an existing envelope depends on its part type:
      • If an envelope was created as a "Part", then the only way to update it is to manually overwrite it with a new envelope which is time consuming and cumbersome.
      • If an envelope was created as a "Lightweight Part", then you have the same option of overwriting as with a "Part" type envelope, but also by copying and pasting the "facet" object. Still time consuming and cumbersome.
    • There should be a way to update existing motion envelopes via the motion envelope creation dialogue box, regardless of the part type or other options selected (mirror solid, mirror body, mirror part, etc.)
      • This could be an option in the envelope tool which the user can choose in order to link the created envelope to the mechanism model it was generated from.
      • Envelopes which have been linked to their generating mechanism would then have the ability to be updated later.
  6. Add an ability to create compound motion envelopes directly
    • Currently, the motion envelope tool can only process one analysis file at a time.
    • If a compound envelope is needed, then the user must create one envelope, assemble it into the mechanism, and then create a second envelope using the first one. Time consuming and cumbersome.
    • You could generate a compound envelope with a single motion path, but this would not capture the entire possible range of motion and this becomes extremely cumbersome with more than two DOF's.
    • The envelope tool should have the ability to process two analyses at the same time in order to generate a compound motion envelope in one go.
      • Order of precedence matters when creating compound envelopes (which analysis is used 1st, 2nd, 3rd, etc.) so the user should have the ability to specify this or more ideally, Creo should automatically detect the correct sequence.
  7. Add debugging tools
    • When an envelope fails to export, what do I do? Where is the problem geometry? What are possible solutions? Currently, the user is on their own.
    • If I was able to export a part-type envelope without the solidification feature then that could be a way to get past an output error, do the export, open it in Creo, and attempt to repair it manually with the IDD.
    • The Invert Triangle Pairs tool is effective at resolving export problems, but it's difficult to tell where problem areas are.
      • When Fix Triangle Pairs is started, mesh statistics should be plotted on the previewed envelope and color coded.
      • Better yet, give an option to have Creo attempt to repair bad geometry.
      • Better yet, make this automatic when an export fails. Creo attempts to fix suspicious geometry and attempts to export again. If it fails again then it prompts the user.
      • But if Creo is able to identify and fix bad geometry, then why should there be an error in the first place?
    • Enable edge display for envelope previews. Currently, you can only see shaded with no edge display.
      • Putting this here since displaying edges during the preview could help the user ID problem areas.
      • The only immediately obvious way to see the envelope edges when troubleshooting a bad envelope is to export a lightweight part.
      • However, you can see the edges when you enter the Invert Triangle Pairs tool.
      • So it is possible to display them during the preview. So let the user control that with the regular edges/no edges display option.
    • Creo should detect if an exported envelope is going to fail upon solidification.
      • And it should tell the user where/why so the user can fix the problem with Fix Triangle Pairs if Creo can't itself.
  8. Add envelope statistics
    • The number of "triangles" is reported when an envelope is created and that's it.
    • What's their average size?
    • How long did it take to generate the envelope?
    • How many triangles have a good aspect ratio and how many are warped and how severely?
      • Plot the statistics on the previewed envelope as color coded values for aspect ratio, etc.
      • This could be a tool for debugging, help with spotting problem areas.
  9. The Motion Analysis tool (BMX)
    • Envelope creation by this BMX tool seems to take much longer than the MDX tool
      • Let's speed it up, please. The ability for this tool to put an envelope quilt in the feature tree of the mechanism it was generated from is too valuable for this slowdown to happen.
    • RegenRequest
      • When the analysis feature is changed from "Always" to "Read Only", the envelope quilt feature should be retained. Currently, it disappears.  If it was retained, then publish geometry can still reference it
      • Better yet, this tool should be able to export a standalone envelope quilt feature that exists independently of the analysis feature that it came from, but still be able to be updated by it.
    • Component Selection
      • Component selection for the envelope ignores assemblies and grouped parts.  In order to select the parts contained within them you must select them all individually.
      • MDX's envelope tool at least allows the selection of assemblies.
    • Update Interval
  10. Better documentation

Great to see that you have written an extensive post about improvements of the Motion Envelope. Sorry to see that there is not much response.


Trying not to be all negative but a problem is that there is not much discussions in the Analysis section in total and in the Mechanism Design section it's almost non-existent. On top of that as far as I know PTC hasn't made one single improvement in Mechanism Design for many years. My feeling without knowing is that there hasn't been any improvement in Creo and that the same features are there as they were in Pro/E Wildfire. The only improvements that springs to mind is 3D Contact which might have been during the Creo era.


I really like the MDO module and we have good use of that even though we are missing key features as creating custom formulas for mechanical component e.g friction damper as you can do in Ansys Motion. It's a shame when MathCad is integrated into standard Creo Parametric that you can't use the power of its formula in MDO.


I'm not sure what PTC's strategy is when they are focusing almost all of their simulation improvements on the Ansys simulation integration and what that leaves MDO for the future. Let's hope that it's not completely dead regarding improvements or new features or that they will integrate a new MDO application based on Ansys.

No worries. I figured this subject, and my deep-dive into it, is too obscure for most.  A post I made eight years ago about motion envelopes got no response and there just isn't much discussion about them anywhere in the community.  So if this post doesn't spur a great discussion, then I hope to at least drum up some votes when we get there.


I think you're right that MDX/MDO is largely unchanged since Wildfire, as far as the function of the tools is concerned. I certainly haven't seen changes to the envelope tool in that time.


3D contact could use some improvements as well. I may have a improvement idea for that in the works...


Here is the Ideas post:

Motion Envelope Improvement Ideas - PTC Community

Please have a look and vote yes!

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