rotating objects getting scaled

[deepblue812]

Working with animating some cars from the Cosmos library and am having an issue when animating the tire rotation. We have a script that will rotate a vehicles tires based on the vehicles position/speed along a path which works fine when rendered in Max, but Vantage is causing some odd scaling when the vehicle gets up to speed. The tire will scale from 100% to about 50% over a couple of frames then go back to 100% over and over until the rotation slows. I thought it might just be our script introducing some kind of keyframe noise or something, so I animated a stand-alone tire with just a keyframe at the start and end of the timeline and am getting the same results.

Any idea what's going on here? Vantage scene attached of just the basic tire animation

[vladimir.nedev]

By default, the .vrscene contains one transformation sample per frame.
Vantage, however, doesn't restrict itself to exact frames. This potentially provides smoother playback, especially if you slow down the animation speed from the Vantage UI.

The missing data is calculated by interpolating neighboring frames. With fast rotation, this can lead to the errors you are seeing.

There are two options available to fix this:
1. open the animation editor, right click on the "scene animation" track and uncheck "frame interpolation" (we should probably make this the default).
This option is saved in the .vantage file.
2. specify more "motion blur samples" for the tires in 3ds Max before exporting the .vrscene file, like you would, if you are rendering them with motion blur in V-Ray.

Greetings,
Vladimir Nedev

[deepblue812]

Thanks Vladimir, unchecking the frame interpolation fixed it. The Vantage playback is definitely smoother with it turned on, but am guessing for rendered sequences it won't matter since it's saving out discrete frames like rendering from Max. Maybe adding a toggle for it to the 'save sequence' dialog would work?
I'll tinker around with the motion blur samples as well, thanks for the tips

[vladimir.nedev]

Maybe adding a toggle for it to the 'save sequence' dialog would work?

I haven't tested it, but maybe the sequence render will work correctly whether you have frame interpolation on or off.
But it needs to be set to use the FPS from the original scene. (the FPS gets loaded from the .vrscene, so unless you change it in the Vantage UI, it's the original one.)

Greetings,
Vladimir Nedev