Over the last few weeks at the studio I’ve been working in Blender alongside 3DS Max and I’ve needed to export 3D bezier curve (spline) data between the two apps. There were a few occasions, such as exporting a logo that I’d cleaned up in Blender from a 2D SVG, and also some 3D animation paths that I’d been working on. While there are a lot of options for exporting other data such as meshes, there’s very little around to facilitate transferring 3D curves between packages.
Wavefront OBJ is supposed to support curves as part of the spec, but functionality is extremely limited, and it’s so rarely used that I can’t find any apps or plugins that actually bother to support this area of the spec. I read somewhere that Autodesk’s flagship format FBX is supposed to include curve data, but in my tests, neither Max or Maya would export curves to FBX anyway, so it looked like they just didn’t bother support it. This makes it a no-go regardless of whether the up-and-coming FBX exporter for Blender supports it or not.
So with no ready made options, I tried an idea – I read up on MaxScript and made a Python script for Blender that takes the curve data and and uses it to generate a MaxScript, that when run inside 3DS Max will generate the same curve using the MaxScript API. There are a few advantages to this, there’s a very fine level of control and you can easily export every feature that’s supported by both Blender and Max, without worrying if an intermediary format supports those specific features too. However there are drawbacks – it’s a pain to use since you have to open up and run a MaxScript each time, rather than just importing a file. I’d rather support an existing standard format, so it’s more widely useful for other people than just me.
I’d been using the ColladaMax plugin (based on the open source FCollada library) previously to transfer meshes and cameras between Max and Blender, and after doing some more research it turns out that the COLLADA format supports 3D beziers, as does ColladaMax. Neither of Blender’s two COLLADA exporters do though, and they seemed too complex for me to add curve support to them, so I grabbed the spec and threw together my own simple exporter for curves only. One very annoying issue is that the ColladaMax plugin (and I presume the FCollada library) expects the data formatted in a way that’s incompatible with the spec. Since my goal here is practicality rather than technical purity, this means that rather than it being a generalised COLLADA format exporter, I have to tailor it to FCollada’s non-standard idiosyncracies. I hope the library is updated to conform to the standard in the future, but going by the devs’ response on their forum it doesn’t look like that will happen any time soon. On the positive side, there’s a good chance that my exported COLLADA curves will work with the ColladaMaya plugin as well, opening up another application to work with. If anyone can test this and confirm or deny, that would be very interesting information.
Anyway, the script is available here: export_curves_fcollada-1.1.py. It’s my first exporter and I didn’t use any fancy XML libraries, so it may be rough (although it gets the job done fine). If any Python gurus have ideas on how to improve it, I’d appreciate some hints! I hope this post might help anyone in the same situation as me, in the ever-perilous business of interoperability.
I’m DISPARATELY trying to find a Blender Tutorial (Video or text) on how to do 3 things.
1-how to make and Animate a Growing Spline
(I know how to do it with Vines, but the results are completely different.)
2-Retop models in Blender and Zbrush
3-How to add Key Shapes to Meshes, Curves and and Lattice without using Armatures (curves and lattice don’t accept armatures).
And help with ANY of these would be of great help.
-Richard