1. Narrative Motion Graphics
Lesson H: Clip Extraction
Tools for making looping clips: Masks, RotoBrush, Color Keying techniques

2. REMINDER: GRAD STUDENT VFX PRESENTATION:
To gain graduate credit in this course students must prepare and present a 5-10 minute presentation on a VFX topic in After Effects. This is typically a presentation about how a combination of effects and systems in After Effects can be used to accomplish a particular visual goal. If the presentation can be delivered with a single effect or in much less than 5 minutes it is likely not a good fit for this assignment. Find one or more tutorials, online or in the suggested text. Submit to the class Piazza “VFX Presentations” folder for approval (first posted, first claimed). Practice and prepare your own typed list of instructions and sample files. Practice again to be sure it can be delivered in 5-10 minutes. Post steps and files in response to your link post, and present in class weeks The grade is for well-prepared materials and a well-delivered tutorial. Choose something you might want to use in your final project, or just that you think is awesome.

3. Project 4: Clip-O-Magic!
Our final project will be to extract and combine clips to make strange videos, playing with form and proportion.
You can use footage that you take yourself (recommended) or that you find online, including the clips provided in this week’s materials.
You should use Color Correction and Adjustment Layers to help elements feel like they belong together and with the background. You can also use footage tracking to composite your strange creations into moving footage backgrounds.
Let’s watch some examples by Cyriak on the course site:

4. Clip Extraction #1: Basic Animated Masking
In After Effects, use Mask Path Animation tools cut out a clip:
CROP: Select the footage layer in the Timeline and crop ([Alt]+[ or ]) the track to the length desired (like a loop).
MASK: At start of the cropped clip, use Pen Mask tool to click-draw around the shape you wish to extract. Use as many clicks/points as needed to surround the shape (and try to predict where you might need more points later, like to surround legs that in the first frame are crossed), but know you will need to keyframe all of them, so try not to get too crazy with the number of control points.
ADJUST: To adjust points for better placement, open mask layer in Timeline, choose Move tool, click away from your Mask and then back on a point so its square is filled while the others are empty. To add or delete points on an existing Mask, hold down the pen tool.

5. Clip Extraction #1: Basic Animated Masking
ANIMATE THE MASK: At the start of the cropped clip, make sure the stopwatch is turned on for Mask Path.
Choose a new frame to keyframe (try to choose a frame that is at least 2-10 frames further along the time, to save work time. Fast moves need every frame). Move control points to new locations for the part they previously touched. For example, the point near the left toe at the start should be near that toe at the all new frames.
Continue down the timeline, adjusting the location of points as needed to surround your form.
Increase feathering to make edges less harsh/rigid.
Note if you add new control points in the middle, you will need to fix their location earlier.

6. Clip Extraction #2: RotoBrush
In After Effects, use the RotoBrush to remove the background:
Select the footage layer in the Timeline and crop ([Alt]+[ or ]) the track to the length desired (like a loop). Double-click this footage layer to open its own view window.
Click RotoBrush in the tool bar (person-with-Brush icon). In Brushes panel choose brush Diameter size (try 20 to start).
About 8-10 frames into the clip, Draw (LeftClickDrag) over the shape. RotoBrush has good edge detection; just gesture through the middle to get a purple outline of the shape. Draw more to add, or hold [Alt] to erase-draw extra bits.
The RotoBrush can resolve 20 frames before and after the draw point. Click 20 frames beyond that to Roto-draw again, if needed.
Move the timebar scrubber inside the layer view to Start, hit [Spacebar] to calculate the full Roto (only calculates gray). Hit [Freeze] to lock it in.
DoubleClick the main Comp to crop the RotoBrush layer back to the length of time needed and see the clip.

7. Clip Extraction #3: Color Keying
In After Effects, use the Color Keying to remove the background in footage shot against a green or blue screen:
Select the footage layer in the Timeline and crop ([Alt]+[ or ]) the track to the length desired (like a loop).
With the layer selected, apply Effect > Keying > Keylight (1.2).
Click the color picker next to Screen Color and then click a color that is near the character (will be a darker than colors further away).
Under Screen Matte adjust Clip Black higher (15) AND Clip White lower (75) to bring back the parts of the character/object that might have been lost due to lighting color bleed from the chroma screen.

8. Clip Extraction #3: Color Keying
QUESTION:
Why choose to shoot against a Green screen?
Why choose a Blue screen?
Let’s watch some examples of feature film green screen work in the film The Great Gatsby (see course site):

9. Animated Masks: Luma Masking:
Once extracted, an animated clip shape can serve as a mask for another layer.
1. Extract an animated shape, as with Chroma keying
2. Apply Effects > Color Correction > Hue/Saturation to this layer and set lightness/darkness to 100% white
3. Place a footage layer below the now white animated shape, like the provided river or flowers.
4. Click the [Toggle Switch / Nodes] button at the bottom of the Timeline stack to make TrkMat available.
5. Select the TrkMat of the lower layer to Luma. This assigns the layer above as a Luma matte, where white areas are visible and black (or empty) are cut away. The upper layer is automatically set to not be visible and the lower footage now appears to be in the moving shape of the original chroma keyed figure. Keep these layers together to maintain the effect.

10. Changing Clip Timing:
To get one clip to match well with another, or to get a clip sequence to work with a sound track, we often need to change the timing of a clip.
TimeStretch
Select the Layer you wish to stretch. Layer menu > Time > Time Stretch.
Enter a new value in the Stretch Factor slot. To set the footage twice as fast, enter 50 (as in, take 50% as long to play). The new duration displays below. If you have a specific timing you want to match, enter Duration instead of Factor.
Hit [OK] to see the new timing in scene.
When Factor is set to over 100%, frames are doubled to fill the space. To reverse the timing of a clip, set the Stretch Factor to a negative value (or apply Layer > Time > Time Reverse Layer).
To undo a Stretch Factor, simply re-enter the TimeStretch window and set the Stretch Factor back to 100.
Time Remap
Select the Layer you wish to stretch. Layer menu > Time > Time Remap. A new attribute appears below the layer in the Timeline, automatically keyed fro the start and end of the film range.
Set keyframes to change the timing as desired. For example, we can create a pause by dropping two keyframes about ten frames apart, and then setting the second keyframe to the same Remap value as the first (note the remaining time will go a bit faster).
Learn more:

11. HOMEWORK 8
Due on Piazza hw8 an hour before class next week: HOMEWORK: CLIP-O-MAGIC (Project 4A): Create 3-5 looping clips (or choose from the provided clips, or search for "green screen" and download off of youtube). Isolate loops by cropping the track to the timing of the loop, mask-out elements (or use RotoBrush or Color Keying), and combine into new moving forms on backgrounds of your choice. FINALLY: Please acquire and read David Mamet's "On Directing Film" before week 9, next week! It is very short, and provides exceptional insights into visual storytelling for film.