Behind the scenes of Episode 2 part 3

So here we are in the final part of this making of blog.

I finished off in the last blog by showing how we tracked an image to fit with the moving image below it.

So here is the problem we’re going to occur if we were to just stick to the exact same procedure as before.

See pic below (Ignore the coloured squares, they’re basically just visual guides for the tracking)


But this looks fine right?? Yep it’s not bad…apart from the small pipe I forgot at the bottom.  But it does the job pretty well.

Except when the boy gets to the point where he crossed the bits I’ve hidden.


Ah Crap!! Actually this would work quite well if it was a scene from Harry Potter, he’s even got the right costume…but unfortunately it’s not!

So what can we do?

Well this is where a technique called Rotoscoping comes in. What’s Rotoscoping? Photoshop would be a good example here but I know not everyone uses paint programs so instead I’ll use this example.

Remember having a scrap book, before the internet days…maybe you still do?  You’d find a photo you loved or maybe a picture from a magazine.  You get a pair of scissors  and cut around the photo and place in in your book.

It’s the exact same thing with rotoscoping except you have to do it to a moving image. And the problem with moving images is they have at least 24 frames per second, if you’re lucky and working in film.  But they could have 25 or even 30,  actually now days they could even have 48 if you’re Peter Jackson.

Anyhow I digress.  So now not only do have to cut out your one picture of the boy, you have to cut out 24, for every second he’s on screen. Or more precisely for every second that he passes over the area that you want him to pass over. In this case I think it was about 1 second so lets call it 24.

The good news is that you can get the computer to help you here and use the same tracking techniques we used before to allow you get your rough cutting to follow where he’s going.  But you still need to go in and refine as key elements change.

For example in the image below notice how  his cloak changes from one frame to the next.


The red lines around the boy are the tools that are used to cut out the areas I want.  This can look different in various packages.  This package is called Mocha Pro

Once I’d cut out the boy I could then put him on top of the wall.  I think the best way to imagine what’s going on is to think of panes of glass.  The very bottom image is your painting, you can’t change this as the paints set and you don’t want to ruin it. But you can make copies of it or even parts. Just like we’re doing here.

For each part you can place it on a pain of glass that sits above the original painting. So in our example we copied a bit of the wall which now sits on top.  The pain of glass would be the same size as the painting but because it’s see through we can only see the solid part we added, in this case the wall.  So to have the boy pass over the top of this wall we need to add a new pane of glass on top of the last pane. And this pane has the cut out boy on it.

So now we have this


Hurray….oh hang on, it still looks weird?

This is the extra problem we have with this particular scene.  It’s his shadow which is also now going behind the wall.  Now if I’d been very organized I may have though ahead and shot this so that no shadow went across areas that had things that needed to be removed. But I wasn’t

So now we have to do the same thing all over again for the shadow. Luckily this isn’t real time so we can skip ahead and show you one I prepared earlier.


Now we’re almost done.  There was another issue here that I won’t go into  too much. So I’d removed all the unwanted items from the wall. But remember this was a static image that I tracked to follow the original background.  The problem with the shadow was that it crossed a lot of these items. So even when I cut the shadow out into its own layer (pain of glass) it still had within it, some of those offending items.

Sorry these examples aren’t great but if you look at the images below you can see how the shadow has the pipe still running through the middle of it.

The first image is just the shadow cut out on it’s own layer (pain of glass) so you can see where the borders of the cutout are.

The second image, is the cutout overlaid onto the background.



So to solve this I use the trusty stamp tool. Remember the tool I mentioned in the first part, where by you can copy bits of an image and paint them over another area.  It’s not the tidiest way of doing things, you sometimes get flickers where the images don’t quite blend so well. On a static photo this isn’t so bad but because you’re seeing lots of frames very quickly this can sometimes be jarring.  But because this was in the shadow I managed to get away with it…I hope?


There were some other technical difficulties with this regarding trying to match the lighting of the static images to the moving ones but I won’t bore you anymore.

The final touches were to add some colour correction and Vignetting.

Vignetting in case you’re wondering it the darkening around the edges of a picture, like you see a lot in old photography.  It’s actually a flaw usually from the lens but because it frames the image so well (and hides rushed VFX) it’s used a lot.


Well I hope you enjoyed this brief glimpse into some of the techniques of the VFX world and I hope it wasn’t too boring or confusing.  If so just send me a message or comment below.

Till next time!


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