Alembic vs SD orientation issues, still a problem.

[redpawfx]

Hi guys, Jesse and I have just run across this issue and I looked back in the archives of the forum and found this...

http://www.realflow.com/forum/viewtopic.php?f=78&t=600
(the thread was started over a year ago and was last updated as still being a problem in june of 2013)

It seems that for some time now the orientation of alembic files has been wrong and not matching what gets exported from maya (or other dcc package) via SD exporter and it still has not been fixed..
This is kinda insane....

I know that I can "rotate and flip an axis" back in maya to temporarily fix the problem, but that's unfortunately, really not the end of the problem...

Additionally, it seems that the curve based transform animation (haven't tested deformation yet) coming from alembic and SD formats do not line up either. I suspect a curve or tangent interp difference between alembic and SD? I assume that the SD is correct and the Alembic is not ? but its hard to be exactly sure what is going on..

Also, FPS changes, if you import your sd and alembic geo, and then change your FPS..
The alembic will scale its time to start and end its animation to the new FPS, so a 24 frame animation at 24 fps will stretch to 36 frames at 36fps. vs the SD will still play back the whole anim in 24 frames.

I made a simple test file in maya, and exported it in both formats.
I can't attach the files, because we're locked down here at work, but this is how to recreate it.

created 3 text objects as ref X,Y,Z placed each on their respective axis,
animated them from 0 to 1 in their respective axis over 12 frames, and then back to 0 by frame 24.

Export the three pieces of geo as SD and ALEMBIC and then bring both into a RF scene with YZX orientation set in the prefs.

The SD will look correct and the motion down each positive axis will be correct..
The alembic file will look like it needs to be rotated around the Y by -90 to line up correctly.
additionally the transforms are reversed so the keyframes on the X object are now on the Z channel
and Z is on the X channel.

I hope these errors can be fixed soon!, its really keeping us from using any of the shiny new features in production, which is a shame.

thanks and let us know!
-johnc

[enrique]

Hi johnc, thank you very much for reporting this.

Unfortunately alembic is "axis agnostic", and there is no way the RealFlow importer could know the axis setup of the alembic geometry that you are trying to import, however we are well aware of this issue and it will soon be fixed. As you said you can fix that in maya as a workaround, but this will not be neccessary in next releases of RealFlow.

About the FPS issue: Alembic exports samples based on time, and when you scale the time in RealFlow (by changing "FPS output" in "Simulation Options") the alembic simulation is correctly scaled, SD on the other hand is based on frames, so if you want to simulate at 36 FPS you must export that SD in maya at 36 FPS. We have just tested it and they both behave in the same way, matching their animations if they are correctly exported. Please let us know if this works for you.

Thank you again for your help, we will keep you updated with the progress.

enrique.

[redpawfx]

Cool Enrique, thanks for the reply.

What about the curve interpolation issue? it looks like the tangent interp between alembic transforms and
SD transforms are different as well..

thanks! and keep us updated.

-johnc

[enrique]

I am not completely sure yet, but this curve interpolation issue might be caused by the same bug. We will have to check this on Monday.
I'll keep you updated for sure! thanks

[redpawfx]

Thank you Enrique, please let me know when you guys have found out something.

-johnc

[enrique]

Hi, we found and almost fixed the bug, there's still one minor problem with the cameras that will be sorted out soon. About the curve animation, I suspect this is the same bug (the problem with the axis) but I am not 100% sure, could you elaborate more or provide an example of this wrong behavior so that I can test it?

We will release a new patch soon with this new fixes.

Thanks.

Enrique.