Subject Overlaying (and stilt walking!)

Hello, I have a question…

What i’m trying to do is take the subject of my videos, Me stilt walking, and cut me out of the back ground using a blank scene of the same location. Then I want to super-impose the cut out me along with many other me’s doing another attempt, over the same background.
In the end, there will be many of me attempting to walk on stilts all together in the same place at the same time.:cool:

Hope this makes a little sense… Thanks in advance!:slight_smile:

Cloning of an element (or actor). Can be hard.

You need to determine the way that you can represent multiple versions. The easiest approach is to allocate a performance space with boundaries that each iteration (of performer) will not cross. Record the multiples then bring them back to blender and perform a crop of each one so they remain in ‘their’ space but all performing at the same time.
Be aware that cross overs include shadows and hard set interaction, this might be bumping into bushes or chairs etc. The hard set must remain unaltered by each iteration unless you have a planned exchange.
Here’s a video i made that demonstrates these techniques:

You don’t have to add the camera wobble.

Another way is to shoot multiple performances of yourself against a green screen. Then replace the greenscreen with your background. But this removes the possibility of interacting with hard set (not easily at least). The benefit here is using a traveling matte, that is the cutout shape follows your performance exactly allowing to to cross those boundaries in front of other performances.

Trying to have the best of both worlds you could create a key from the existing background plate, but it is very hard. You would shoot the performance(s) against an unchanging hard set, then strike the talent and shoot a lock off of the set. Take the lock off and subtract it from the performance version to create a travelling matte (of the performance). This aproach tends to get a lot of contamination from similar colors in the background and foreground.

Yes, I am fimiliar with this meathod, here are some of my videos on that:

(sorry, I don’t know how to embed, I’m new here! :slight_smile: By the way, Nice camera tracking! my quality is too low and computer too slow for that… )

 What I'm having problems with is that I have already filmed my stilt walking and I was walking around my yard from one point have having different levels of success each time (thus, My selves occupied the same space many times...) The camera was not moved and the background was steady.  I was hoping to use this fact to create some sort of mask, similar to green screening but not green.  then I would overlay the multiple me's over the same background.  Hope this helps a little!


The problem with the subtraction method is color contamination and compression artifacts. Both damage the quality of your matte shape. Another alternative would be to roto by hand all the cross overs. That is use the mask tool to animate a shape around each charater at the point they cross each other.

If I were to give this method for a spin, do you think I would use the chroma key node? I should be able to filter out a bit of noise if I messed around with in… Any suggestions or alternatives?

Chromakey works because the background that you are trying to separate is supposedly uniform. Any deviation from that color becomes the mask shape. Unless you’re moving over perfectly green AstroTurf I doubt you will be able to pull a good key.

Well, Here you go, a have made something! Maybe not perfect but ok’ish…

I used the a difference key and changed the mask with blurring and erode and such, used multiply to put them together and had a bit of color correction (not the best choice? not sure what I should do instead…) a bit of tweaking and this is the result.


It isn’t perfect and I would do it differently next time during filming… but I think it looks kind of cool with the invisible people! This has only 3 people but in the future it will have 8 if I can pull it… We’ll see. :slight_smile:

Depending on your background colour you may be able use brightness and contrast etc to output something that you can pull a Luma Key from. For example if your background is the sky (being on stilts this might well be the case) this is usually over exposed and is great for keying using a Luminance Node. If, however, your background is a wall or fence or just a general background then it is going to require Rotoscoping which dependent on your level of overlapping with your other subjects can require a lot of detail in your mask.

I’m just going through rotoscoping out an actor from a scene to allow for digital elements to be added behind, I’m doing this using the masking tools and they are really good but it’s painstaking work in the detailed parts.

I covered the basics of this before the masking tools were implemented in the first episode of my youtube channel but the principles can be applied to the masking tools.

Hope this helps.


Yes, this is all very kind of you all to post! thanks for all the feed back! :slight_smile:

I have seen many of these videos before and I think that rotoscoping could be a mess because my characters, as you saw in the video in my previous post, are all right on top of each other and the background is not quite that contrasting. As of now, It seems my only choice is to re-shoot…
Too bad because those were the first few hours of stilt walking for me… :frowning:

If any one has any other suggestions for this that do not include the need to re-film, that would be nice, but otherwise, I’m not sure what to do because now I’m really good at stilt walking and I won’t fall over anymore on my own.


Thank you again for all the help! I am really liking this site! Many friendly and nice people just waiting to help out! Thanks so much!!! :slight_smile:

Bad news is that big movies solve this problem the same way. Roto monkeys and lots of man hours. Sorry