Motion blur sub steps. Tweet

[PackMen]

Hi!

I have a realistic setup for a car where the wheels are spinning very fast (it goes a 100mph) and octane makes the wheels disappear.

I know it is something to do with motion blur steps, or sub-sampling, or whatever it is called in octane. But WHERE are those settings in v3? It is late and I must be blind but I can't find it anywhere.

Thanks a lot in advance!

[face_off]

I know it is something to do with motion blur steps, or sub-sampling, or whatever it is called in octane. But WHERE are those settings in v3? It is late and I must be blind but I can't find it anywhere.

From memory, you need to tick Use Modo Shutter Speed - and setup sub-sampling in Modo (ie. set a very large Camera->Motion Blur->Shutter Speed FPS). But it's been a while since I have looked at this, so feel free to send me your scene so I can take a closer look if you can't get it working.

Paul

[PackMen]

Hi Paul,

Thanks for getting back to me. I've spent some more time trying to find a solution to no avail.
Unfortunately there is no such thing as motion blur fps or subframe in Modo. Modo's built in renderer doesn't need that. It just works.
But octane seems to struggle with spinning geometry. But I hope I'm not the first monkey on the moon with this problem and there is some fix to this.

Also it would be very helpful to know where are the substep settings in the standalone version.

Here is a screenshot where you can see the wheels shrinked to a tiny speck in the middle of the wheel-arches:

And here is the simplified version of the modo scene so you can investigate it further:
https://www.dropbox.com/s/cktd3ojd7iukgb7/octanebug_mblur_wheels.lxo?dl=1

Thanks!

[PackMen]

I have also prepared another scene to illustrate motionblur issues with fast spinning objects. This time it is a helicopter rotor.

Here is a gif to illustrate different blur length settings: 50%, 100% and 200%.

If you look carefully even at 50% the blade ends shaping into a much smaller radius arch then they should be. I mean they don't look like a part of a bigger circle.

Again, here is the modo scene to play with:
https://www.dropbox.com/s/vapjktdjlhr51ld/octanebug_mblur_rotor.lxo?dl=1

I tried to export the whole scene to orb and opened it in standalone where it produces the same error so I don't think it is modo or plugin related so please let the other devs know about this.

It would be great to know how to fix this as right now I'm stuck with these projects. Fortunately they are just home projects but I'd be in deep soup if it would be an actual job...

Thanks again!

[face_off]

Unfortunately there is no such thing as motion blur fps or subframe in Modo. Modo's built in renderer doesn't need that. It just works.

If you tick Use Modo Shutter Speed, the Modo subframe settings should work in Octane.

But octane seems to struggle with spinning geometry. But I hope I'm not the first monkey on the moon with this problem and there is some fix to this.

I think the issue in this instance is that the wheel rotation is being controlled by the Wheel_Rotation_Control item, so is not being correctly applied to the Placement node of the Wheel mesh items. If you "octane.saveAnimation" (forcing vertex rather than object motion blur), and render in Octane Standalone, the wheels will then render correctly. Alternatively, if you set the wheel rotation in the transform of each of the wheels, it should work too (although I didn't try this to confirm).

If you look carefully even at 50% the blade ends shaping into a much smaller radius arch then they should be. I mean they don't look like a part of a bigger circle.

Good pickup. Yes, this appears to be an Octane render issue. I have reported it to Otoy.

Paul

[PackMen]

Hi Paul,

Thanks for looking into the scene file. I really appreciate every minute of yours so I tried to make things easier for you.
I recreated a simple scene from scratch and got rid of the controller that drives the anim.
The rotation is now directly applied to the object and even baked to every keyframe.

As you suggested I've used "octane.saveAnimation" to force vertex motion blur and saved it to OCS.
Unfortunately Octane Standalone also failed to correctly render it producing a different look.
Increasing the sub-frames in the batch animation script didn't fix the issue.

Please see the scene file here:
https://www.dropbox.com/s/foff0dyuwmdrq1p/octane_bug_wheelspin.zip?dl=1

Here is the render comparison on Vimeo:
https://vimeo.com/211182475

I think I have similar issues to this guy:



He later got it solved somehow:



And here is another good example with fast spinning wheels without errors:



Thanks a lot Paul and the rest of Otoy to look into this issue.

I'm so keen to see this one getting solved.

Cheers,
Kristof

[face_off]

Hi Kristof

There are a couple of issues here....

1) When you render an animation in OctaneRender for Modo, it is calculating the wheel rotation motion blur from the wheel transform rotation each frame. Whereas when you export to OCS/ORBX via octane.saveAnimation, the motion blur is render from the vertex velocities rather than the wheel transform. Both methods have issue, but the issue is different in each case.

2) When rendering inside the plugin - the problem is the sub-frame calculation to sample the rotation between two frames is not right. The sub-frame time calculation if based on the Modo scene FPS - however I don't think that the Modo renderer is actually using the scene FPS for it's calculation of motion blur. So I will need to look into this in more detail, and go back to the original test files I used when first implementing sub-frame sampling.

I will report back here when I have more info.

Paul

[PackMen]

Hi Paul,

Thanks again for the continuous support, especially on Sundays! And sorry about posting the same issue in the Facebook group. I didn't mean to flood the whole internet with this issue just thought it might be a good idea to ask the guys there too.

I too am (with my very limited toolset) trying to figure out what is going on and not just sitting back waiting for the magic to happen.

I might actually found a little breadcrumb here! The problem may very much be in Modo itself, namely in the ABC exporter.

So what I've done is I've launched Maya and imported the ABC file that Modo generates upon "octane.saveAnimation" and used the Keys>Bake Simulation command to see the animation curves that came through in the alembic.
As I've expected the curves are messed up. I think it is called euler flipping.

As a next step I've exported a new ABC (and later an FBX) from with Modo's own export command and re-imported that again in an empty Modo session.

Please click on the GIF below to see the results. They aren't look good at all.

So maybe all that's happening is Octane reading this buggy alembic that Modo has produced. That would explain why Cinema 4D users don't have this issue. They maybe have an euler filter in the ABC exporter. But that still doesn't explain the jump in scale values...

Again, I'm not a technical guy so this can be rubbish. But nevertheless it is interesting to see that Modo isn't even compatible with itself...

Cheers,
Kristof

[face_off]

Hi Kristof

I have added a new property to the Kernel->Animation settings so that you can setup subframe animation. If you set "Animation Samples Per Frame" to 10, it seems to resolve the issues on the helicopter and wheel rotation scenes. This is when rendering animations within the plugin only. It is not working correctly with the octane.saveAnimation command - which I am still working on. Can you try for yourself pls and let me know how you go?

3.6.3.118 Pre-Release
- Added Frame Step to the Kernel->Animation panel, to allow progressing more than 1 frame when rendering an animation
- Removed the empty Defaults panels
- Fixed issue where daylight animations were not render correctly in animations and not exporting correctly with octane.saveAnimation
- Rewrote the sub-frame animation system. Added "Animation Samples Per Frame" to allow sub-sampling of Live Geometry Update mesh items. Increase this property value to increase the number of samples taken between Modo frames. You must refresh the scene in order for this setting to take effect.

https://render.otoy.com/customerdownloads/plugins/3b/20/d8/36/OctaneRender_for_Modo901_3_6_3_118_64bit.exe

Thanks

Paul

[PackMen]

Hi Paul, that again is fantastic support! Thanks for implementing that so quickly.

As soon as the VR version is out, I'll definitely try it out and get back to you.

Cheers,
Kristof