Highlight text to annotate itX
In the previous video, you looked at how to do basic tracking and stabilisation in the Axis Timeline FX.
The last function we will cover in the Axis effect is the keying tools.
In an earlier video, I inserted a background plate of the coliseum on track 1 of the sequence.
I have already added the corresponding green screen source media onto track 2.
I have also added an Axis Timeline FX to the segment so we can get keying straight away.
Let’s go into the Axis editor and in the center of the controls, you will see the Keyer button.
This is your first entry point into the keyer.
Inside the keyer, you have seven chroma keyers to choose from.
Each composite has it’s unique set of problems to solve,
and several ways to solve them, hence the multiple ways to key an image.
The default keyer that is applied to the image is a luminance key, hence the result in the viewer.
For this example, you will be using the Master Keyer at the top of the list.
The first step in the workflow is to remove the key colour.
Click on the left grey colour pot and the cursor will turn into a colour picker.
Using the master keyer, click and drag across the green in the viewer.
When you release the cursor, the master keyer samples an average of the green colour
and applies the appropriate key.
The result looks pretty good but in order to make it perfect,
you need to see the alpha or matte channel generated by the master keyer.
Press F3 to see the matte or alpha channel view.
You can tell what you’re looking at, by looking at the view mode box at the bottom left of the screen.
In the usual tradition of keying tools and understanding mattes…
Black is transparent, grey is semi-transparent and white is opague.
You can see there are issues in the tunnel part of the shot.
You can fix this in three ways.
Firstly, you could click anywhere on the image and the on-screen sliders will allow you
to adjust the different luminance levels in the alpha.
Secondly, you could adjust the histogram and Matte controls
to adjust the black and white colours in the alpha.
This is good in some instances but it could get rid of good detail.
Finally, the method we will use is patching.
This method allows you to work on isolated areas of the key.
Under the sampling title, you can change the pull-down menu to patch 1
or press SHIFT+1 to choose patch 1.
You can sample an individual pixel by clicking on it
or you can hold CONTROL+SHIFT and drag a box selection around the pixels.
Notice how Smoke automatically picks the right color to add or remove areas from the matte.
You can keep dragging boxes over the regions until the areas are fixed.
You can also tweak the sensitivity of these patches in the sliders below.
I’ll just use a second patch by pressing SHIFT+2
and sample the black areas to ensure they are 100% transparent.
Let’s switch back to the result view using the pull-down
or by pressing F4 to see the result so far.
So the alpha channel is looking really good right now, but the colours have gone a bit strange.
This is because the keyer uses Automatic colour suppression by default.
This is often called spill suppression in other keyers.
You can adjust the range slider, if too much of the key colour has been suppressed.
In addition to suppression, you can also colour correct your keyed image within the keyer.
Click CCF to enter into the familiar colour corrector.
I’ll quickly switch to the colour warper,
and use the colour matching technique that I showed you in the video
about colour correction in the sequence.
Once that is complete, I’ll press return to exit the colour warper back to the keyer.
One other area you need to work on when doing keys, is the edge blending.
Keys usually land up with dark or bright edges and they need to be balanced,
to correctly blend in with their backgrounds.
By dragging the Luma slider, you can see of the edge brightness
adjusts and you can match it so that the key better sits in the background.
One final task in keying is rotoscoping.
Let’s say that I want to remove this pillar to the right of the gladiator.
I can’t key it because it is not green but I can mask it out.
Switch to the Matte view through the pull-down menu or press the F3 keyboard shortcut.
In the keyer, you can switch to the Gmask menu.
Gmask is short for garbage mask, for masking out areas of your image.
You might call this mask in other applications.
To create a gmask, click on the ADD button.
You can now click and drag a shape around the pillar.
You need to close the mask to complete the shape.
Either click on the first control point or click the close button.
And Smoke will complete the shape for you.
The closed shape is filled with white.
This means that the masks contents are opaque.
Click on the colour slider and change the value to 0 to make the masked selection black,
which is transparent.
To feather the edges of the mask, drag the offset slider.
If you want more refined edges, you can switch to the advanced edge gradients
and adjust the feather on a control point basis.
The shot does move slightly so I’ll turn on Auto-key and I can animate the mask.
You can click to select individual control points or press COMMAND and click and drag a box selection.
You can animate the control points of the mask, individually, in a group, or the whole shape.
I’d like to mention that you could also use the Stabilizer tool
to track individual points if you wish, or the overall shape.
Switching back to the Result view by pressing F4,
will show you the keyed result with the applied mask.
You can press the return button to exit the keyer.
Press the exit button in the axis Timeline FX to return to the sequence.
You can now scrub the segment to preview the result
or press the render button to render the final output.
In the next video, we go beyond timeline layer-based compositing
and start exploring the ConnectFX procedural node-based compositor.