Thanks for the tutorial. I had to pause many times and rewind but I was able to get a part modeled I've been wanting to do for awhile. The cup example was good, I enjoyed that as my first entry to cad. I like solvespace, it seems fairly barebones but it works!
That's good news! Remember that CadQuery (mentioned in the video) may help you deal with more complex projects as your skills increase. Thanks for writing!
Great tutorial, from zero to something useful!. I'm new to CAD and this has been one of the most useful tutorials I've seen. Thanks a lot! Also kudos to the developers of SolveSpace. There's some very fine programming there (the executable is 6 mb!). That's some old school fine programming there.
Thanks for watching and for commenting! You may be aware that I favor free, open-source programs, and SolveSpace is one of the best of that breed. Stay tuned for more videos in the future!
Pretty good video but I almost died when you went to extrude/difference inside the cup ;-) That was bound to trigger NURBS faillures for multiple reasons. Better to end the handle sketch inside the wall of the cup - maybe draw a vertical line in there and split the curves against it? When switching to triangle mesh, we do recommend putting that switch as far down (not up) the construction history as possible. I just submitted a PR (not accepted yet) to make dimensions on ARC entities default to Radius instead of Diameter because this video reminded me that's usualy what we want. Also, S is for "segments" O is for "On" and right-click ends your line segment without starting a new one ;-) And Q is for "eQual" I guess, but nobody mentions this and the keys seem arbitrary. Best I can tell G is for "green" which is the default color for construction lines !?!?
> "Better to end the handle sketch inside the wall of the cup" Yes, I sometimes make unwarranted assumptions about a program's internals. My favorite program for this activity was the old Pov-Ray, which relied entirely on CSG ( www.povray.org/documentation/view/3.7.1/28/ ), pure mathematics, no polygons. In that environment, everything worked as one would expect from mathematics. No surprises. Thanks for writing!
This was very helpful, thank you. For a future video, an explanation of how to make assemblies would be very helpful. Likewise a slicing operation, where you take an object and slice it in two along an arbitrary plane
Great video (even though I have not watched to the end yet)! I've been thinking of making a comprehensive SolveSpace tutorial similar to this for more than a year. It almost fells like you've read my mind :-)
> ... It almost fells like you've read my mind :-) Well, maybe, but IMHO SolveSpace is a terrific and neglected program. It deserves some love. Thanks for writing!
Good tutorial. I also went for FOSS solutions, and I found both solvespace and freecad. Freecad at glance seemed more advanced and solvespace seemed more like learning basics platform. All I need is something to feed my 3d printer. Freecad I suffered through designing one or two parts, but at some point I just gave up on it, highly frustrating. I went for solvespace and learned most of it. Came in here for helix how to use it to make threads. My only gripe with solvespace is one project for soldering iron box that required me to compile solvespace for 64 bits as it was runing out of ram. Also the framerate went to like one frame per 5 seconds. Im not sure why, but it struggles a lot with more complex projects - or I don't know how to make it in a way that it won't. (if anyone is curious I can provide file for it, be aware, requires x64 build). And the red lines sometimes get to you (even though NURBS solves 99% of occurances)
> Freecad I suffered through designing one or two parts, but at some point I just gave up on it ... The same experience here, exactly. > Im not sure why, but it struggles a lot with more complex projects ... Just a suggestion, in the configuration dialog, try changing the "chord tolerance" and "max piecewise linear segments". These adjustments operate in mnore than one dimension, so they can greatly improve speed and reduce memory consumption, in exchange the screen drawings look less aesthetically appealing. The upper two adjustments affect computatiion and display, the lower two affect exported meshes. This means you can have a high-accuracy export (created slowly) while speeding up the editing phase. > And the red lines sometimes get to you (even though NURBS solves 99% of occurances ... I find that if I never allow two 3D vertices (of different subassemblies) to occupy the same location in space, those errors go away. I do this by deliberately adding a tiny value to some dimensions to avoid collisions. But in most cases more RAM and a faster processor would solve the other issues. Just saying, I know this may not be feasible. I hope this helps.
@@lutusp yes, i am aware of chord tolerances. Sometimes though even when its at 0.2% / 10 when project is complex enough, it struggles hard. I dont think I can grab better cpu (solve space is single threaded afaik). My machine is pretty strong (ryzen 5800x / 80gb od ram) , but solvespace is 32 bit program by default, so by default it is limitted to 3-4 GB of ram. Thats why i recompiled it to 64 bit and then the memory limitations go away for me. I will try adding small spacing next time i have problems with the red lines. I hope it will not be enough spacing to fool my slicer to put there actual gap. Thanks for tip.
@@by010 I agree SolveSpace is single-threaded, I mean AFAIK. I guess my designs aren't that complicated, so I don't see the issues you describe, and my local install, like yours, is compiled in 64 bit. I try to design complex things in pieces to avoid to much complexity in any single file. I do know this -- all the really powerful CAD/CAM programs are closed-source, and most are expensive as well. Thanks for writing!
Hi! With step and rotate you ended up with 1 DoF. I've checked and it seems to be the angle by which the elements are rotated when stepping. Is there a way to constrain that so that it is fully constrained?
Hi -- without a context, without a diagram, it's not easy to identify possible reasons. Sometimes the menu item "Analyze" ... "Show underconstrained points" (Shift+Ctrl+F) can help. This feature lights up points that aren't properly constrained. I hope this helps -- thanks for writing!
The biggest problem I know so far about FreeCAD is filleting irregular shapes and topological naming problem. How does Solve space do in these two areas?
To be direct, SolveSpace's filleting is less robust than in FreeCAD, and AFAIK the TNP has the same status -- it's not directly addressed or mitigated and is only less an issue because SolveSpace's projects tend not to be as complex as those in FreeCAD. I would be happy to be corrected about this view, but it's to the best of my understanding. The issue in both SolveSpace and FreeCAD that I find most annoying is the fact that you cannot change an element from which other elements spring without destroying the entire assembly. That would require a level of code robustness that neither program possesses at this time. The main reason I prefer SolveSpace over FreeCAD is that the former is less opaque to a new user. There are times with FreeCAD where I have no idea how to take he next step and the documentation doesn't help, or a feature isn't robust enough to accommodate what one might call s common-sense approach. Thanks for writing!
The video is supported by a Web page: arachnoid.com/Computer_Aided_Design This link is also in the video's description text. The Web page includes the SolveSpace source for the final cup design, linked here: arachnoid.com/Computer_Aided_Design/SolveSpace_files/cup_new_design_400ml.slvs But definitely read the entire article, which includes many more SolveSpace source files for different projects. Thanks for writing!
You are most welcome! I'm happy to hear it served your needs. And I don't understand why more people aren't using SolveSpace, which IMHO is a terrific program, easy to use.
@@lutusp problem for solvespace for me is there is no global variables and functions, i do model parametric gears with involute curve profile in freecad but it is not so easy on solvespace, possible but harder. actually solvespace fits me more but that feature is a bit important.
@@user-cg9dc9ig5v Yes, it's true there are no explicit global variables, but one group can rely on the dimensions of another. This means if you plan a task carefully, you can make subsequent groups entirely dependent on previously defined dimensions, by simply selecting the desired dimensions in later groups. But I agree that it would be better to have explicit globals. Thanks for writing!
>> "Solvespace does not allow constraints for multiple objects in version 3.1." Actually it does. But if you select everything using Ctrl+A, that selects everything -- lines, points and all. That will fail. If instead you select only the lines and press 'Q', they're all forced to be equal length. My tutorial uses this equal-length feature multiple times -- once for all sides of a triangle in the bolt's thread prototype, another for all sides of a hexagon in the same section for the bolt head design. The video shows me explicitly selecting the six sides required for my hexagonal bolt head --- but by selecting the lines one by one, not using Ctrl+A. Not wishing to make unwarranted assumptions, I just tested my understanding with four lines having random arbitrary lengths. Then I explicitly selected the lines squentially until all four are selected. After applying 'Q', a square appears. If instead I use Ctrl+A, the experiment fails because that creates a collection of lines and points. Hey ... try it. But don't select everything with Ctrl+A, instead explicitly select lines before applying 'Q''. And thanks for writing!
@@lutusp Thanks for your answer but I don't use Ctrl+A, I select lines one by one like in your video. As a result, the following message appears: "Bad selection for equal lenght / radius constraint This constraint can apply to: - two line segments (equal lenght) - two line segments and two points (equal point-line distances) - a line segment and two points (equal point-line distances) - a line segment and a point and line segment (point-line distance equals lenght) - four line segments or normals (equal angle between A,B and C,D) - three line segments or normals (equal angle between A,B and B,C) - two circles or arcs (equal radius) - a line segment and an arc (line segment lenght equals arc lenght)" So as you can see you cannot constraint 6 lines in Solvespace 3.1, at least in the Windows version (multiple lines constraint will be in the next version). Also the constraint of 4 lines does not result in a square with equal sides. Maybe the linux version allows you to do this.
@@eryk7545 I just downloaded and tested the Windows version of SolveSpace 3.1 and it's ... well ... not current, not synchronized with the source. For my Linux environment I've been compiling SolveSpace from source (there isn't a prepackaged Linux version), and it seems the source differs from the Windows release versions including 3.1. I apologize for this, it's rare and unprofessional to have unsynchronized sources, but the latest SolveSpace source, required for a Linux installation, isn't present in the Windows version. So, sorry, but it seems my tutorial doesn't cover the precompiled Windows version in all respects. You can still get the results I show, but the steps differ. Specifically you have to specify equal lengths for pairs of lines, not more than two at a time. If you're dedicated to SolveSpace, you can compile from source on Windows as I did on Linux, in which case my tutorial is correct in all respects. And finally, thanks for bringing this to my attention.
@@paulkahler6373 > "No, 3.1 does not allow that. " Context is important. On Linux, where compiling from source is the norm, the currently posted 3.1 version provides the feature. Nevertheless, I should have tested the currently available Windows version (which doesn't have the feature) before relying so much on the feature in my video. As always, thanks for writing.
It depends on how you mean "rotate". But try holding down the Ctrl key and right mouse button while dragging the mouse for one kind of rotation. Then try pressing the Shift key and right mouse button while dragging, for another kind. I hope this helps.
Sorry, I can't figure out which key you're describing. If this is still an issue, perhaps you could give me a time in the video so I can see the problem for myself. It might be "rectangle", which uses the R key. I hope this helps.
@@lutusp At 50 minutes into the video, when I'm trying to replicate the drawing, there's always an error when I do shift+l, exactly at that moment it also appears in the top left corner of the video saying to type this combination of a penguin figure + r and I couldn't associate it on my keyboard, maybe it is the cause of the error?
@@natanaelmelo9481 Okay, I figured it out. The "Penguin+R" is actually my pausing the screen recorder, it's not a SolveSpace command. Please disregard it and wait for the next actual command. And just in case there are more of those, just ignore any "Penguin+characteer" commands, they're not for SolveSpace. My screen recorder has its own commands, and I sometimes pause the video screen recording to catch my breath. The keyboard recorder dutifully records those keystrokes -- I'll have to think of a way to prevent that. Anyway, when you see the penguin, just ignore those keystrokes. I hope this helps.
@@lutusp lol ok, my friend, thank you very much, now I understand. As for the error that was appearing, it was resolved by limping a box (force nurbs surface to triangle mesh)
Hey Paul, thank you very much for this tutorial! And I agree with you - SolveSpace deserves more love, simple yet powerful 🙂
You are most welcome -- I'm glad my tutorial is finding an audience, along with SolveSpace itself.
Thanks for writing!
Thanks for the tutorial. I had to pause many times and rewind but I was able to get a part modeled I've been wanting to do for awhile. The cup example was good, I enjoyed that as my first entry to cad. I like solvespace, it seems fairly barebones but it works!
That's good news! Remember that CadQuery (mentioned in the video) may help you deal with more complex projects as your skills increase.
Thanks for writing!
Great tutorial, from zero to something useful!. I'm new to CAD and this has been one of the most useful tutorials I've seen. Thanks a lot! Also kudos to the developers of SolveSpace. There's some very fine programming there (the executable is 6 mb!). That's some old school fine programming there.
Thanks for watching and for commenting! You may be aware that I favor free, open-source programs, and SolveSpace is one of the best of that breed. Stay tuned for more videos in the future!
I love your commentary. It's absolutely brilliant.
Thank you for this tutorial
You are most welcome! I'm planning more SolveSpace tutorials.
Pretty good video but I almost died when you went to extrude/difference inside the cup ;-) That was bound to trigger NURBS faillures for multiple reasons. Better to end the handle sketch inside the wall of the cup - maybe draw a vertical line in there and split the curves against it? When switching to triangle mesh, we do recommend putting that switch as far down (not up) the construction history as possible. I just submitted a PR (not accepted yet) to make dimensions on ARC entities default to Radius instead of Diameter because this video reminded me that's usualy what we want. Also, S is for "segments" O is for "On" and right-click ends your line segment without starting a new one ;-) And Q is for "eQual" I guess, but nobody mentions this and the keys seem arbitrary. Best I can tell G is for "green" which is the default color for construction lines !?!?
> "Better to end the handle sketch inside the wall of the cup"
Yes, I sometimes make unwarranted assumptions about a program's internals. My favorite program for this activity was the old Pov-Ray, which relied entirely on CSG ( www.povray.org/documentation/view/3.7.1/28/ ), pure mathematics, no polygons. In that environment, everything worked as one would expect from mathematics. No surprises.
Thanks for writing!
This was very helpful, thank you.
For a future video, an explanation of how to make assemblies would be very helpful.
Likewise a slicing operation, where you take an object and slice it in two along an arbitrary plane
I've added this to the new video: ruclips.net/video/blkjW0JauX8/видео.html
I hope it explains things clearly enough.
Thanks for writing!
Great video (even though I have not watched to the end yet)!
I've been thinking of making a comprehensive SolveSpace tutorial similar to this for more than a year. It almost fells like you've read my mind :-)
> ... It almost fells like you've read my mind :-)
Well, maybe, but IMHO SolveSpace is a terrific and neglected program. It deserves some love.
Thanks for writing!
Thank you for such well made tutorial. I can do some simple practical stuff with SolveSpace now!
You are most welcome! I'm glad to see this video finally being recognized, along with SolveSpace itself!
Thank you Paul for the awesome tutorial. Can you please offer your opinion on OpenSCAD if you have one :).
Thanks for the heads-up, I don't know about OpenSCAD and I'm going to try it out. Thanks for writing!
Idea for another video: I couldn't find a SolveSpace tutorial anywhere on making Bent Pipes or Elbows. You should do one.
Good suggestion! It's not difficult, but also perhaps not obvious. This is now on my list.
Thanks for posting!
Good tutorial. I also went for FOSS solutions, and I found both solvespace and freecad. Freecad at glance seemed more advanced and solvespace seemed more like learning basics platform. All I need is something to feed my 3d printer. Freecad I suffered through designing one or two parts, but at some point I just gave up on it, highly frustrating. I went for solvespace and learned most of it. Came in here for helix how to use it to make threads.
My only gripe with solvespace is one project for soldering iron box that required me to compile solvespace for 64 bits as it was runing out of ram. Also the framerate went to like one frame per 5 seconds. Im not sure why, but it struggles a lot with more complex projects - or I don't know how to make it in a way that it won't. (if anyone is curious I can provide file for it, be aware, requires x64 build). And the red lines sometimes get to you (even though NURBS solves 99% of occurances)
> Freecad I suffered through designing one or two parts, but at some point I just gave up on it ...
The same experience here, exactly.
> Im not sure why, but it struggles a lot with more complex projects ...
Just a suggestion, in the configuration dialog, try changing the "chord tolerance" and "max piecewise linear segments". These adjustments operate in mnore than one dimension, so they can greatly improve speed and reduce memory consumption, in exchange the screen drawings look less aesthetically appealing.
The upper two adjustments affect computatiion and display, the lower two affect exported meshes. This means you can have a high-accuracy export (created slowly) while speeding up the editing phase.
> And the red lines sometimes get to you (even though NURBS solves 99% of occurances ...
I find that if I never allow two 3D vertices (of different subassemblies) to occupy the same location in space, those errors go away. I do this by deliberately adding a tiny value to some dimensions to avoid collisions.
But in most cases more RAM and a faster processor would solve the other issues. Just saying, I know this may not be feasible.
I hope this helps.
@@lutusp yes, i am aware of chord tolerances. Sometimes though even when its at 0.2% / 10 when project is complex enough, it struggles hard. I dont think I can grab better cpu (solve space is single threaded afaik).
My machine is pretty strong (ryzen 5800x / 80gb od ram) , but solvespace is 32 bit program by default, so by default it is limitted to 3-4 GB of ram. Thats why i recompiled it to 64 bit and then the memory limitations go away for me.
I will try adding small spacing next time i have problems with the red lines. I hope it will not be enough spacing to fool my slicer to put there actual gap.
Thanks for tip.
@@by010 I agree SolveSpace is single-threaded, I mean AFAIK. I guess my designs aren't that complicated, so I don't see the issues you describe, and my local install, like yours, is compiled in 64 bit.
I try to design complex things in pieces to avoid to much complexity in any single file.
I do know this -- all the really powerful CAD/CAM programs are closed-source, and most are expensive as well.
Thanks for writing!
@@lutusp is there a restriction on writing replies on this video? It seems if I write any reply it does not get posted?
@@ruevs thats youtube thing. They often figure out some comment is censor-worthy and hide or delete it. It is what it is
Hi! With step and rotate you ended up with 1 DoF. I've checked and it seems to be the angle by which the elements are rotated when stepping. Is there a way to constrain that so that it is fully constrained?
Hi -- without a context, without a diagram, it's not easy to identify possible reasons. Sometimes the menu item "Analyze" ... "Show underconstrained points" (Shift+Ctrl+F) can help. This feature lights up points that aren't properly constrained.
I hope this helps -- thanks for writing!
The biggest problem I know so far about FreeCAD is filleting irregular shapes and topological naming problem. How does Solve space do in these two areas?
To be direct, SolveSpace's filleting is less robust than in FreeCAD, and AFAIK the TNP has the same status -- it's not directly addressed or mitigated and is only less an issue because SolveSpace's projects tend not to be as complex as those in FreeCAD. I would be happy to be corrected about this view, but it's to the best of my understanding.
The issue in both SolveSpace and FreeCAD that I find most annoying is the fact that you cannot change an element from which other elements spring without destroying the entire assembly. That would require a level of code robustness that neither program possesses at this time.
The main reason I prefer SolveSpace over FreeCAD is that the former is less opaque to a new user. There are times with FreeCAD where I have no idea how to take he next step and the documentation doesn't help, or a feature isn't robust enough to accommodate what one might call s common-sense approach.
Thanks for writing!
very useful. thank you.
You're most welcome! I'm glad to see people picking up on SolveSpace. I think it deserves more exposure than it's gotten so far.
How did you refine the cup handle at the end of the video?
The video is supported by a Web page: arachnoid.com/Computer_Aided_Design
This link is also in the video's description text.
The Web page includes the SolveSpace source for the final cup design, linked here: arachnoid.com/Computer_Aided_Design/SolveSpace_files/cup_new_design_400ml.slvs
But definitely read the entire article, which includes many more SolveSpace source files for different projects.
Thanks for writing!
thank you so much for that video
You are most welcome! I'm happy to hear it served your needs. And I don't understand why more people aren't using SolveSpace, which IMHO is a terrific program, easy to use.
@@lutusp problem for solvespace for me is there is no global variables and functions, i do model parametric gears with involute curve profile in freecad but it is not so easy on solvespace, possible but harder. actually solvespace fits me more but that feature is a bit important.
@@user-cg9dc9ig5v Yes, it's true there are no explicit global variables, but one group can rely on the dimensions of another. This means if you plan a task carefully, you can make subsequent groups entirely dependent on previously defined dimensions, by simply selecting the desired dimensions in later groups.
But I agree that it would be better to have explicit globals.
Thanks for writing!
Nice video, but how did you set all lines to equal length at the same time? Solvespace does not allow constraints for multiple objects in version 3.1.
>> "Solvespace does not allow constraints for multiple objects in version 3.1."
Actually it does. But if you select everything using Ctrl+A, that selects everything -- lines, points and all. That will fail. If instead you select only the lines and press 'Q', they're all forced to be equal length.
My tutorial uses this equal-length feature multiple times -- once for all sides of a triangle in the bolt's thread prototype, another for all sides of a hexagon in the same section for the bolt head design.
The video shows me explicitly selecting the six sides required for my hexagonal bolt head --- but by selecting the lines one by one, not using Ctrl+A.
Not wishing to make unwarranted assumptions, I just tested my understanding with four lines having random arbitrary lengths. Then I explicitly selected the lines squentially until all four are selected. After applying 'Q', a square appears. If instead I use Ctrl+A, the experiment fails because that creates a collection of lines and points.
Hey ... try it. But don't select everything with Ctrl+A, instead explicitly select lines before applying 'Q''.
And thanks for writing!
@@lutusp Thanks for your answer but I don't use Ctrl+A, I select lines one by one like in your video. As a result, the following message appears:
"Bad selection for equal lenght / radius constraint
This constraint can apply to:
- two line segments (equal lenght)
- two line segments and two points (equal point-line distances)
- a line segment and two points (equal point-line distances)
- a line segment and a point and line segment (point-line distance equals lenght)
- four line segments or normals (equal angle between A,B and C,D)
- three line segments or normals (equal angle between A,B and B,C)
- two circles or arcs (equal radius)
- a line segment and an arc (line segment lenght equals arc lenght)"
So as you can see you cannot constraint 6 lines in Solvespace 3.1, at least in the Windows version (multiple lines constraint will be in the next version). Also the constraint of 4 lines does not result in a square with equal sides. Maybe the linux version allows you to do this.
@@eryk7545 I just downloaded and tested the Windows version of SolveSpace 3.1 and it's ... well ... not current, not synchronized with the source.
For my Linux environment I've been compiling SolveSpace from source (there isn't a prepackaged Linux version), and it seems the source differs from the Windows release versions including 3.1.
I apologize for this, it's rare and unprofessional to have unsynchronized sources, but the latest SolveSpace source, required for a Linux installation, isn't present in the Windows version.
So, sorry, but it seems my tutorial doesn't cover the precompiled Windows version in all respects. You can still get the results I show, but the steps differ. Specifically you have to specify equal lengths for pairs of lines, not more than two at a time.
If you're dedicated to SolveSpace, you can compile from source on Windows as I did on Linux, in which case my tutorial is correct in all respects.
And finally, thanks for bringing this to my attention.
@@lutusp No, 3.1 does not allow that. The current development version does. It's one of the big improvements coming for 3.2.
@@paulkahler6373 > "No, 3.1 does not allow that. "
Context is important. On Linux, where compiling from source is the norm, the currently posted 3.1 version provides the feature.
Nevertheless, I should have tested the currently available Windows version (which doesn't have the feature) before relying so much on the feature in my video.
As always, thanks for writing.
¿Es seguro descargarlo, hice un escaneo con Virus total y me dice que tiene un malware?
solvespace is not malware - it is safe if you download it from solvespace.com/ -- be sure you download from this URL.
Thanks for writing!
@@lutusp Gracias, ya lo descargue y lo probé. Era un falso positivo que dió la licencia.
@@________________ buenas noticias! Y gracias.
how to rotate a drawing in solve space with the mouse
It depends on how you mean "rotate". But try holding down the Ctrl key and right mouse button while dragging the mouse for one kind of rotation. Then try pressing the Shift key and right mouse button while dragging, for another kind.
I hope this helps.
@@lutusp Thank you very much, it worked
@@natanaelmelo9481 You're welcome. Some SolveSpace users have complained that the rotations aren't intuitive, but I think over time it gets easier.
For God's sake. What is this penguin + r key?
Sorry, I can't figure out which key you're describing. If this is still an issue, perhaps you could give me a time in the video so I can see the problem for myself. It might be "rectangle", which uses the R key.
I hope this helps.
@@lutusp At 50 minutes into the video, when I'm trying to replicate the drawing, there's always an error when I do shift+l, exactly at that moment it also appears in the top left corner of the video saying to type this combination of a penguin figure + r and I couldn't associate it on my keyboard, maybe it is the cause of the error?
@@lutusp But anyway, thank you very much for your attention, I'm just starting out in solve space and I'm already learning a lot from your videos
@@natanaelmelo9481 Okay, I figured it out. The "Penguin+R" is actually my pausing the screen recorder, it's not a SolveSpace command. Please disregard it and wait for the next actual command. And just in case there are more of those, just ignore any "Penguin+characteer" commands, they're not for SolveSpace.
My screen recorder has its own commands, and I sometimes pause the video screen recording to catch my breath. The keyboard recorder dutifully records those keystrokes -- I'll have to think of a way to prevent that.
Anyway, when you see the penguin, just ignore those keystrokes. I hope this helps.
@@lutusp lol ok, my friend, thank you very much, now I understand. As for the error that was appearing, it was resolved by limping a box (force nurbs surface to triangle mesh)