Issue with animated fov...wild jumps on certain non-keyframed parts of sequence

[fixeighted]

Hopefully someone can help work out what is going on here. This is a cut scene with my camera move and a box to see what is occurring. https://www.dropbox.com/s/j9xw4u72ye...LITCH.max?dl=0

One keyframe at beginning and end for movement...that is all totally fine.
One keyframe at beginning/end for an fov change and f# change.
At two points, one near the beginning and one near the end the view jumps, like a sudden zoom.
The animating values appear to be even, so I am at a loss to explain or fix it.
Maybe a bug in the matrix?
We do have many other shots with animated fov, so it would be a shame to lose all of that functionality...

EDIT: So it seems it's an issue with simply animating the fov. If I animate the focal length it is fine.
However, given that I need to match cameras that come from Vantage, those cameras, set in Vantage, do not use the same interpretation of values, meaning that I have to also animate the film gate to push the view back into relative position. Alongside this I need to use an online converter to translate Vantages values to Vray camera's values, as they are bizarrely not the same.

All of course making the most basic of operations extremely complicated

Only 52 shots left to go.....*sigh

[hermit.crab]

Thanks for the provided scene. The issue occurs because of the Film Gate, which is always in millimeters. I guess the value in Vantage may adapt with the unit setup, though I need to test this out. Otherwise, set the value to 36, rather than 0,36 and you're good to go.

[fixeighted]

Hi,

Thanks for the response, but if I leave it at 36 this still occurs and is why I noticed initially.
Subsequently the only way I got it to match was to animate the gate for the beginning and end, matching those framings, so that .36 fraction worked as expected.
My Max scene units are metres for this project so I guess that the mm in the Vray camera is not correct and has to be adjusted down to match the scene scale.

I am at least now hopeful I have a workflow for the remainder of shots. It's unnecessarily complicated doing what I'm doing but there was no other option, given the glitches.
Sad face

Sorry if I am incorrect about any of this...please try it yourself to confirm. I have been wrong-footed by this for a while now and so am a little confused each time I see another conflict.

EDIT: I now have this working without the glitch and using non-silly gate animation. I have no idea how.
I did however find that in Vantage the F# is also the wrong scale in relation to the aperture size and needs to be set as the images suggest.

[hermit.crab]

Tested the camera glitch again and a 36mm film gate, indeed solves the issue. So you might have made a mistake in one of your tests.

I think your aperture size value is wrong. The formula is:

f-number = focal length / aperture size

To find the aperture size equivalent of the f-number would mean dividing the f-length (16mm) to the f-number (1.6), which gives you a value of 10mm.

[fixeighted]

Thanks for your continued input; not at all surprised if I made a miscalculation somewhere, as it's been very confusing tbh

We do seem to have things a little more settled in terms of matching the blur.....I think...

Our main hurdle that still exists is trying to get a camera out of Vantage that renders the same in Max, so that it matches Vantage's render.
I think I explained that in one of the other posts but it's really annoying.
It goes; how do you reliably create a 100 frame sequence in Vantage that exports a camera with the exact same 100 frame sequence?
Nothing we tried so far has accomplished this, as a 100 frame sequence in Vantage always results in a 101 frame move in Max, thus it can't possibly match.

So am I missing something so stupidly obvious that solves this, or is there currently no way at all to do this?

[hermit.crab]

That's a known issue (internal bug-tracker id: LAV-745), which is waiting for developer investigation. You'll need to manually adjust it to match in 3ds Max.

[fixeighted]

Thanks for that info.
However it's impossible to adjust it to match in Max as any keyframe repositioning results in a differently timed sequence, unless I misunderstand you.
What is happening is the first and last frames in both Vantage, 0 - 100, and Max 0 - 100 are exactly the same, though the time is different, as Vantage is effectively clipping the
actual final frame.

We discovered this entirely by accident, resulting in the workflow below. Otherwise we would still be going in circles

Set the shot in Vantage to be 100 frames and export that camera.
This camera comes to Max with 0-100 frames
I export that camera to a .vrscene and that is imported back into a Vantage scene which has more than 100 frames (arbitrary length)
Now when rendered from Vantage that process can simply be aborted after the correct 101 frames have rendered (as there is no way to control output length).

It is clunky and time consuming but it works, and is now how we can reliably get the shots done.