Hi Michael,

I'm trying to export some curves using MoI DXF export (polylines option), and I have funky results inside Modo.
Reopening the dxf file back in MoI give the expected results, so something is wrong in Modo.
Based on the posted image, can you give me any info about what's going on ?

Hi PaQ, that's a pretty weird result. It generally follows the right shape but seems somehow grid snapped or quantized into a small range of numbers or something similar to that...

It's kind of similar to what might happen if you were dealing with really super large or super tiny coordinate values, where loss of precision ends up causing a type of jumping between values. I guess something related to that is my best guess of what's going on.

It does not look like your objects are at any particularly large or small scale though so I don't know why Modo would be trying to apply some kind of huge or small scale to it at import time though.

Do you want to post the DXF file so I can test with a couple of other programs too just to make sure there's nothing actually wrong with the DXF file itself?

- Michael

Hi Michael,

Thanks for the precision explanation, it makes sense.
Here's the original .3dm and the .dxf output.

Units in MoI are Cm, in Modo I use metric/centimeter unit.
Using the MoI lwo option : Scale output unit in meter, I have perfect scale result when exporting geometry in .lwo format.

However, when using the .dxf, object comes 100* bigger in modo, so a 30 cm length curve = 30 m in modo.
Maybe this scaling difference is the reason of this loosing precision problem.

Hi PaQ, I tried loading the DXF file into Rhino and ViaCAD and even Adobe Illustrator and it comes in as expected in all of those, so as far as I can tell there isn't anything wrong with the DXF file itself.

As far as I can tell it looks like some kind of bug in the Modo DXF importer.


> However, when using the .dxf, object comes 100* bigger in modo, so a 30 cm length curve = 30 m in modo.
> Maybe this scaling difference is the reason of this loosing precision problem.

You'd have to have a lot more scaling happening than that to lose precision to the extent to get that type of noticeable coordinate quantization. More like scaling by 1/100000000000000 or so.

Units with DXF files are kind of tricky, the setting for which unit system the DXF file is actually in is fairly obscure and so a lot of programs don't know how to find which units the file coordinates were in. Some programs give an option that shows up at import time where you can pick the units but it sounds like Modo just assumes meters. So you might want to switch units to meters before doing the DXF output to match what Modo is expecting to see in the DXF file.

- Michael

Hi PaQ,

it must be a bug in the vers. you are using. I checked it under OSX modo 401 and 601 and it's coming in fine. Haven't checked the scale though.

Regards
Stefan

Hello,

Thanks a lot for the input guys, I have open a bug report for 701 sp2