How to create a realistic sky replacement

Hello, and welcome to HitFilm Express 2017. I’m Axel from HitFilm, and in this tutorial
we are going to learn some basic compositing techniques, using a shot from Westworld to
Yuma. Here’s the shot we will be recreating, which
hopefully doesn’t actually look like a visual effects shot. If you are new to compositing,
or filmmaking in general, then you may not realize how frequently this type of invisible
visual effect is used in films, or how easily you can use them to improve your production
value, or to simply create shots that you couldn’t actually film. I encourage you
to download the project files that accompany this tutorial, so you can follow along.
In this shot we have a building which looks great, but we weren’t allowed to actually
get up on the roof, as it wasn’t built for that. So, our second element is our actor,
who was filmed separately. To make it look like he is standing way up on that roof, though,
we need to match the camera angle, so he is standing on a ladder so we can get the camera
down underneath him. In both of those shots the sky is quite boring, but that also means
that we have a nice even background to shoot against, that should help us to cut out the
elements we want, as we will see later on. Also, both these shots include trees that
we don’t want, so we are going to remove those. For the sky, I ended up using this
photo of Port Townsend, Washington, which I took a couple years back from the deck of
the Coupeville ferry. It has the sort of thin, wispy clouds the shot required. So, let’s
get started putting these all together. We will start with the building. In the Media
panel of HitFilm, right-click that building clip and choose Make Composite Shot. In HitFilm,
there are two types of timelines. The Editor timeline is used to place your clips in sequence,
one after another, and build your final project. The second type is a Composite Shot timeline,
which is used to combine multiple layers and create a single shot, which is exactly the
situation we have on our hands here. So, we make a composite shot, and our building video
is added as the first layer. Now we will use a mask to remove everything except the building.
There are three mask tools in the Viewer of any composite shot. The Rectangular and Ellipse
masks quickly create rectangular or circular shapes. The Freehand Mask tool is the one
we will use, it lets us draw whatever shape we want, by clicking to add control points
wherever we need to. Click the Mask tool, then select the layer you want to add the
mask to. Then click on the edge of the building to start masking. As we draw the mask, you
can zoom in on the viewer using this menu or your mouse wheel, to see what you are doing
more accurately, and you can pan around in the Viewer using the right mouse button.
Proceed around the edge of the building, placing points at the corners and working around the
smaller details. It doesn’t really matter where you start, just carry on until you get
back to where you started, then click the first point again to close the shape and complete
the mask. If you need to fine-tune any of the mask points, just drag them to adjust
their position. Once we have the mask done, we can add our
new sky in behind it. So, find the Port Townsend Sky image in the media panel, and drag that
onto the timeline. If we drag it below our Roof layer, it will be added below it. You
can drag the layer names up and down to change the order of the layer stack. The sky in the
image is a bit too high to fill our frame, so we need to move it down. All the controls
for the position and size of a layer are found in its Transform controls. These can be accessed
on the timeline, or in the Controls panel. Switch back from our Mask tool to the Selection
Tool, then move the layer downward until only the sky is visible by dragging the green arrow
in the viewer, or by dragging on the Values next to the position property. The first value
is the X axis, from left to right, and the second value is the Y axis, from top to bottom.
Now for the third element, the character. Let’s drag that clip onto the timeline,
and take a look. We could use masking to cut him out, too, like we did with the building,
but you will find, if you try that approach, that it is no fun. We need a lot more points
to create a shape this complex, and the dude is moving, so we would need to reposition
all of those points on every frame of the video. This is a process called rotoscoping,
and it is still used a lot in visual effects work, but only when absolutely necessary.
We will use another technique in this case, called keying, which will save us a lot of
time. You might be familiar with the use of green screens in filmmaking, which is a common
type of keying where you select a specific color and remove it from the footage. In this
footage our sky doesn’t have much color info, though, but it is nice and bright, so
we will use a different kind of keying, called Luminance Keying, that lets us select and
remove the brightest areas of our footage. But first, we can quickly remove most of the
footage using a mask. Use the Rectangle Mask tool this time, and just drag a rectangle
around our actor. Make sure its big enough that when the actor moves, he doesn’t leave
the mask. By removing most of the sky with the mask, it will make it easier to create
a clean key, which we will do now. In the Effects panel, open the Keying folder and
find the Luminance Key effect, then drag it onto the actor layer. It will affect the layer
right away, but not the way we want it to. By default, Luminance Keying is set up to
remove black, so we want to change the Key Type to Key out Brighter. Then, we can adjust
the Threshold to determine exactly how much will be removed. It helps to zoom in on the
Viewer, so you can see the edges better while you dial that in. A threshold of 1.00 leaves
everything, and as you lower that, more and more of the footage will be removed. The trick
is to find the setting that removes everything you need it to, but not to go too far, and
remove part of your subject. I find that 0.6 works well for this shot.
I’m going to pause for a second to point out that you have just used your first effect
in HitFilm. There are 370 effects and presets in the Effects panel, for a wide variety of
different purposes, but the basic process for using all of them is the same as what
we just did: drag the effect you want onto the layer you want to apply it to, then adjust
its Controls to get the result you want. Getting back to our composite, we need to
move our character layer below the building, reposition it and resize it. These are techniques
similar to what we did earlier, so you are familiar with them. Drag the layer name down
below the building layer. Open the Transform properties and adjust the Scale to shrink
him down to better match the size of the building, to around 70%, then reposition him so his
toes are just visible over the edge of the building, like he is standing on the edge.
His angle doesn’t quite match the building though, if you look at the vertical siding,
so let’s edit the Rotation property a bit until it does. You can change the rotation
on the viewer by dragging the blue square handle, or by dragging the value in the Controls.
About 12 degrees is looking much better, then adjust the position again, so his feet are
lined up properly with the edge.
This is almost done, the bulk of the work is behind us, and all that remains is to fine-tune
a couple things. Mainly, the edge of the roof is looking a little bit harsh, and there are
a couple of things we can do to help that. First, in the Mask controls, we can feather
the edge of the mask a bit. Just one or two pixels is enough, we don’t want the edge
to look blurred, we just want it to blend ever so slightly with the sky behind it. The
second thing we can do is add Light Wrap. At the top of the Effects Panel there is a
search box. You can type in the name of any effect, like Light Wrap, to find it quickly.
Drag Light Wrap onto the roof layer, then double-click it to open its controls. Light
wrap lets you choose another layer, and wrap the brightness of that layer around the edges
of your selection. So open the Source Layer menu, and select the Port Townsend Sky layer.
This takes the brightness of the sky and wraps it onto the edges of our roof.
We want this effect to be quite subtle as well. The radius defines the width of the
light wrap, so bring the Radius down to 5 or 6, and set the Opacity to 0.7. In many
cases, it is the little adjustments like this that really make the difference in creating
a convincing composite, and Hitfilm includes powerful tools to let you dial these in.
Since our character is facing to the left, the composition of the shot might look a little
better if he was positioned over on the right side of the frame. Since each element of our
shot is a separate layer, its easy to adjust the composition however you like. If we want
things more to the right, we can just select our Roof layer and our Man layer, then shift
them over. Easy. And there is our final shot! Let’s watch
it! That was easy, right? In just a few minutes you finished this composite, and learned the
basics of masking, using effects, Keying, and matching elements to create a new result.
Now, if you switch back to the Media panel, you will see our composite shot listed there,
along with our media clips. And just like you can drag media clips onto the Editor to
build your finished project, you can also drag composite shots onto the editor, and
sequence them with video clips. So thanks for watching, and I hope you found
this tutorial useful. Make sure to check out our other Westworld tutorials as well, for
more tips and training on using HitFilm Express 2017.

How to create a realistic sky replacement | HitFilm Express

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