Two questions about fixing perspective

rgbiirgbii Website User Posts: 965 Just Starting Out
Hello folks, this is boring compared to the fun special effects HitFilm can do, but I do have a couple of questions about fixing perspective.
I shot some video of a play, and there really wasn't a perfect place to put the camera. It would have been nice to have the sensor parallel to the back wall of the stage, but because of where I had to put the camera, to get the whole stage, the camera had to be both tilted down, and to one side, which of course caused the perspective to be off (a tilt-shift lens would have been nice). I originally hadn't planned to fix it since for this, it's not that important, but I got curious if HitFilm could fix something like this.
My two questions are:
1) If anyone has done this, what did you use to do it?
2) In Perspective warp, what is the difference between Swing and Roll? They seem to do the same thing to me.

So far, Perspective Warp does an Ok job.
Quad Warp seems to do a pretty good job too, probably better than Perspective Warp.
I'm betting Bezier Warp could do a nice job too, but didn't seem to have an advantage over Quad Warp.
Thanks in advance for any help,
Richard.

Comments

  • NullUnitNullUnit Website User Posts: 791 Just Starting Out
    If I'm understanding you right you could just rotate the image a little until it's straightened and then zoom in a little so that the image fills the frame. which you can do in both versions of HitFilm.
  • rgbiirgbii Website User Posts: 965 Just Starting Out
    It's more than just rotation. The left part of the pic is as-shot. As you can see on the right vertical lines lean to the right, and on the left side, they lean a bit to the left since the camera was off center to the right, pointing down a bit, and pointed left a bit. The right is after applying Perspective Warp to correct it. Seems to work, though could be better. I don't have an example handy to show, but I think Quad Warp might work better.

    [attachment=390:Perspective3.jpg]
  • ZedFableZedFable Website User Posts: 136
    When you first described it, I thought the angle was much more drastic then it turned out to be but actually, with the perspective warp applied, I think it looks pretty great!
    I looked at them for awhile, but I don't believe there are any tells in the image on the right that give away the fact that it is corrected. Is there something specific you are trying to improve over the image on the right?
  • AxelWilkinsonAxelWilkinson Staff Administrator, Imerge Beta Tester, HitFilm Beta Tester Posts: 5,238 Staff
    Another option which might be fun to try, just because HitFilm can, is to convert the video to a 3D plane, and then just turn the plane to counteract the angles created by the camera position. The result you came up with looks pretty good to me; I'm not sure which of those warp tools might have an advantage over the others in this case.
  • rgbiirgbii Website User Posts: 965 Just Starting Out
    Thanks Zed. Not really trying to improve on it, just curious what others might be doing. If it's faster or easier. HitFilm has a 'grid' that I through on top to help align the verticals, which helped a lot since it was done by eye.
    I come from a photography background and most editing programs have a tool to correct perspective. They normally have two lines you drag around on the image to tell it what should be vertical (or horizontal), and it does the rest. Didn't know if HitFilm had something like that.
    My initial reason for posting was to find out the difference between Swing and Roll :)
  • rgbiirgbii Website User Posts: 965 Just Starting Out
    Hi Axel, I actually did play with that. It could worked, but seemed to take longer than the perspective warp tool. Maybe someone with more experience tweaking things in 3D might do better than I did :) Any idea what the difference is between Swing and Roll in the Perspective Warp? They seemed the same to me, but I'm assuming there's some difference.
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