Is rotoscoping realy needed?


#1

Hi there!

I got a question in connection with the following scene.
I would like to place a 3D object over a movie clip. The problem is that the place where it is placed is surrounded by some trees which are “flying” below the 3D object and this looks quite bad.

Is there any working path to solve such issues? How would you handle this?

I would be pleased to hear from you!



#2

It’s really difficult to tell from the images you’ve posted as they’re about 2px wide, but it looks like you’re in need of some work to create a clean plate from the footage. This will integrate better with any CG that you plan to insert into the scene.

Depending on how the scene has been shot you may be able to create loose mattes to roto out anything that’s messing with your track. You feed these mattes (or roto shapes/whatever) into your tracker and it disregards any blips under the mattes.

Alternatively (and at least in syntheyes AFAIR) you could manually track the scene by creating your own blips/trackers in areas you can see have good parallax etc. you may be able to avoid roto entirely using this method, which may save quite some time.

Dan


#3

Hi! Thank your for your answer.

Could you be so kind and go into more detail about the workflow? Which program should be used and if there is any tutorial about it?

I have both pictures in a bigger size, but I cant upload the entire clip. :wink:

Thanks!


#4

You can use any* compositing package to create clean plates out footage.

In terms of workflow, you need to start at the storyboard stage of a production, make sure you’ve got good angles to track, and if you haven’t you need to speak up so that the director knows that the shot will cost more (or just not happen at all). Once the location is confirmed you can go out and shoot some texture reference. Then on the day of the shoot get out and shoot some lighting reference (grey ball + shiny ball) and some reference frames for tracking in case you desperately need them. This will all go into making the final shot a bit easier to complete.

Personally there’s no way I would have chosen that shot to track because of the amount of stuff that’s in the way. It’s going to take a long time to track in all the patches you’ll need to create a reasonably believable patch of ground big enough to obscure the trees.

The first thing I would do after getting a rock solid track is create some proxy geometry and get that in the scene, over the top of the trees. Assuming that your track is good it’s then just a matter of texturing it effectively using reference from the scene you shot.

Honestly, I think that this might be a challenge too far because of the angle of the shot, the scale of the geometry you’ve inserted (it looks far, far too big compared to the scale of the old castle) and the fact that the track looks like it’s at the wrong angle. If you pull this off I would love to see the result!!

*as long as they support some sort of 3D space, examples would be Nuke, Fusion, AE, Blender


#5

Hi Daniel!

Thank you for your response. I am the director and the producer and all the other guys in one person because this is my thesis. :wink:
That is why I won’t cancel it anymore. Maybe I have to adjust the storyboard a bit, or I will change to a full 3D scene. Maybe a wireframe view from some angles could solve that problem.

I am afraid to tell you that the scale should match. I have built it from a handmade model and it matches very nice actually. If the tracking it self is nice, it is not a problem at all. The only problem is the tree-thing which I would like to solve in the best possible way.
That is why I wrote that post here. :wink:

I think I could handle it to post the final result later on. :wink:


#6

Apologies if I’m wrong, but your asking about the trees appearing behind the castle when they should appear in front. Mainly at the bottom of the frame and a few sections screen-left.

And this shot itself is a flyover of the castle rather than a hovering camera shot?

If that’s the case and your trying to avoid rotoscoping individual branches. There are a few things you could potentially do…

Use garbage mattes to create rough outlines on the trees in specific areas - then use luminance/colour keyers to try extract the branches from the background. Depending on the variation in luminance/colour you might be able to extract some mattes using this technique by combining soft mattes with harder edge mattes. You’ll have to do this in sections.

The second is to make stills of the trees in question and put them on cards. You then paint out the trees from the original footage or replace the ground with a 3d ground plane and place the cards in the scene where they would be.


#7

You don’t have to apologize for anything about that.

The sequenzes are mainly circling movements around the spot of the castle, yes.
Others are some “stills” from different angles and the drone was just hovering. The main thing is, that there are threes where over hundrets of years ago the castle has been.

To your advices:

Would you say that I could use a GM made by 3ds max by rendering out the object IDs and invert that mask?
On the other hand I have not done combinding of such maps you wrote about.

The second option is a bit hard to follow. What exactly do you mean with “on cards”
Do you mean planes with the imagesequence mapped on it?

I would be pleased if you could offer me a bit more details.

Thank you in advance and kind regards!


#8

The advice kind of varies depending on the movement in the shot. With lot’s of movement you’ll probably have to do a lot of manual work to make it work - and unfortunately this means you’ve got to do lot’s of rotoscoping.

This is the type of thing that we’d consider replacing the trees in the plate with CG trees. It’s a lot easier for a matte painter or texture artist to paint a realistic ground texture around the castle and then render CG trees on top of it.

As far as garbage mattes go, they’ve got to be where the trees are - so it’ll be easier to create them in 2d with roto. If you can place shapes in 3d which represent the volume around the trees then you could render object IDs as well.

With the cards method - use just a still (not a sequence) and use it as an opacity mapped texture on a polygon plane in 3d. Render that out and comp it over the castle where it needs to be.


#9

Yes, you are right. I am afraid to tell you that the most shots got much movement. And in addition to this I got a huge amount of frames. Well I could minimize the work by preselecting the different scenes, but I am not sure if this saves soooo much time.

If I got you right I should roto all the scenes I would like to use “naked” in After Effects or what ever and then use this mask to place the layer over the combined one (naked with 3d).
I have already tried it with the rotobrush tool. The result takes muuuuuch time for the usability that I get out of it.
Do you think just a simple one with a feather could work for that?

I still not sure if I got you right - sorry for that.
Do you mean to render it out with the IDs and invert it in the compositing? After that I got an inaccurate mask for those trees which has to be adjusted just a bit?

I am sorry to bother you again with that. :wink:


#10

Hey, sorry for the late reply.

I get the feeling this may have got confused up a bit - I’m confused myself.

To go back to the original problem… “you want to composite the castle into the shot, but at the moment the trees in the plate appear underneath the castle when they should appear in front of the castle”.

The techniques you could use to do this are…

[ol]
[li]remove the trees from the plate and replace them with 3d trees (modelled, textured, etc)[/li][li]remove the trees from the plate and replace them with 2d trees (on cards)[/li][li]roto out the trees and composite them correctly in screen depth.[/li][/ol]For the “cards” method. Google “trees opacity mapped” and look at some of the images, hopefully that can explain it better than words.


#11

Hey,

not a problem at all. I have already had finished the work on that project, but I restarted working on it to do some adjustments on. I think I will have to rethink about the possibilities you have given me. :wink:
The 3d trees should be the easiest of the given solutions. (If I don’t have to work out every single part of the trees :D)

Edit: the problem for the rotopart is that the brow is most of the time hard to distinguish from the ground which is brown too.
I have tried out to roto one tree quick and dirty but the problem of that looking is the shadow.
Even with a simple drop shadow it looks almost like the 90’s. :frowning:
The card thing:
I got some white edges on my cards which are working quite fine for some 2D layers which are placed just by eye although.