Interpolation curve problem in Track Motion

Jessariah67 wrote on 10/20/2003, 10:29 PM

Got a situation, and I can't figure it out...

I have three video tracks that I want to bring down in "thirds" across the screen. I created the first "strip" by cropping, then moving the Track Motion to the left. I set two key frames -- both in the "end" position I want. I then select the first of the two, set the X, Y in the Track Motion window to U/D only, drag the event up and out of the viewing field. I preview, and it slides straight down, just like it should.

I try to do this on a second track, filling the middle of the screen, and when I drag the event to the top, Vegas creates a curved interpolation line. I preview, and the first section comes down perectly straight, but the second tails in on a curve. I erase the keyframes and stat over. Same things happens. Then, suddenly, the same thing is happening on the first track as well -- the one that was working fine beforehand. Now, no matter what I do, If I drag the event straight up, the interpolation path gives it a curve. I have tried:

1) Junking all events and starting from scratch --still happens.
2) Deleting keyframes on the Motion Track timeline and redoing them -- still happens.
3) Changing the smoothness setting AND the linear, slow, fast, etc. settings. Each setting changes the curve slightly, but there is still a curve.
4) Erasing all previous keyframes on the track and "starting fresh" by setting a "hold" keyframe of a RESTORE setting at the beginning -- it still happens.

There are "red arrows" at the beginning & end of the interpolation lines that look like they could adjust the curve, but I have had no luck figuring out how to adjust them (if that's even possible).

I resolved the problem by setting the events as fixed in their finished position and "bringing them down" by using a PUSH transition, but what I was doing SHOULD HAVE WORKED, and I can't figure out why it did at first, then didn't (even on tracks that it was working on at first).

Eagerly anticipating your thoughts as I scratch my head...

Comments

farss wrote on 10/20/2003, 10:40 PM

I've had exactly the same head scratching over this sort of issue. It seems that VV thinks you are trying to define a path for the motion and traces out where you've moved the frame to. Of course this isn't what we want to happen.

But I'm still not exactly clear on what you want to happen. From what you've described it sounds like you want each event to start of full screen and then move and shrink into it's place in the screen.

If that's not what you want i.e. you want each clip to start and end in the same spot then you need to go to the first frame and set only one keyfame there. If you want to make any adjustments make certain you are only woriking on the first keyframe, you need to zoom in on the time line within the pac/crop window to see that you haven't added more keyframes.

If you have more than one keyframe then VV will interpolate between them.

Hope that helps.

Spot|DSE wrote on 10/20/2003, 11:35 PM

Kill 'smoothness' or rather, set it to zero, this should go away.

Jessariah67 wrote on 10/20/2003, 11:53 PM

Thanks for the input...

FARSS -- Before I do anything, I adjust the pan/crop & framing within Track Motion to create the "slice" I want, then I work with the movement in Track Motion by setting the identical keyframes and adjusting the first one so that it is "directly above" the second. There is absolutely no change in "size" of the event -- either through pan/crop or Track Motion. This is entirely movement related. I have two identical keyframes, 2 seconds apart. I grab the first and drag it straight up and set the keyframe to linear & "0" smoothness, which means that it should come "straight down" to the second keyframe over the two seconds. But when I drag it up, it draws a curved interpolation line, instead of a straight one. No matter what I do, I can't change the fact that the line curves. Setting different keyframe modes "changes" the curve, but nothing will make it "straight."

SPOT -- I tried killing smoothness. It didn't do anything except "adjust" the interpolation curve slightly.

What gets me is that it originally worked in a track, then put the curve in without me doing anything. Could the .veg file be corrupted somehow?

farss wrote on 10/21/2003, 3:01 AM

So you are trying to get it to move between two keyframes, glad we cleared that one up. Having said that though I'm at a loss to help much more other than to suggest you try using even pan / crop rather than track pan / crop. These do work differently just to further confuse things.

Another thought, try rendering the clip out at just the reduced size and then make that move, maybe its just the combination of size and motion throwing it off. Sorry I don't have a definative answer. I'll fire up the VV box and see what I can make happen.

farss wrote on 10/21/2003, 3:17 AM

Update,
I can get it to work right and also reproduce your problem. If I change the size at anywhere other than the first keyframe on the timeline it combines that with the motion to produce a curved path.

In the pan/crop window make certain you have the TL locked (little padlock button) for all the tracks you are working on. Close window go to the very first frame, note how VV always has a keyframe there. At the point adjust the size of each clip and position them where you want them. Make certain at this point you only have one keyframe on each track.

Now if you want the clips to stay where they are for a duration move along the time line to where that is. Insert another keyframe on each track at that point, it'll have the same dettings as the first one. Now move along to where you want them to finish the motion (2 secs later?). Clip the double crossed arrow icon to constrain motion to vertical and drag down to bottom of frame making certain you don't change the size of the window.

All should work OK!