Webtorial: 2-Point Tracking

Transcription

1 This webtorial will show you how to use 2-point tracking to attach a missing arrowhead to its clock hand and track the hand s movement to ensure that the arrowhead stays on its hand as it rotates. You will need to track the dot at the tip of the arrowless clock hand as well as the centre of the clock. Finally, to improve the look of the effect, you will then animate the feathering on the arrowhead to simulate motion. Note: It is important that you read the Download instructions. To print the instructions, right-click the page and select Print. You will be using the following clip: ClockMan.mov Media Download 2-Point Tracking footage (1,256 KB) Setting up the Sequence 1. Create a new sequence with the following settings: - Video Format: NSTC D1 4/3 - Resolution: Full/Uncompressed 2. In the Avid Explorer, navigate to the location of the media. 3. Right-click the ClockMan.mov file and select one of the following: t Link to create a linked file in your sequence s folder 1

2 t Capture to capture the file 4. Navigate to the folder where you linked or captured the file and drag the ClockMan clip to the timeline. Finding the Center-point of the Clock 1. Scrub through the clip. Notice that the arrowhead is missing from the tip of one of the clock hands and there is a white dot in its place. Note: You can also open the Graphics Combo view by Ctrl clicking the Graphics layout button. It is a floating view that can be accessed from anywhere to perform graphics and painting tasks. 2. Go to the beginning of the clip. 3. Click the Graphics layout button in the taskbar to switch to the Graphics layout. 4. Select Polyline as your Gfx Creation tool and set the properties as follows: - Paint Style: Brush > Use - Brush: Shape > Ellipse, XY radius = 3, Deselect Soft Edge - Brush FX: Color Blend > White - Masks: RGB - Time Span: Start to End 2

3 Webtorials Avid DS Nitris Select tool Freehand tool Polyline tool Edit Shape tool 5. Click the tip of the arrowless clock-hand and draw a straight line (stroke) from the tip to an approximate centre of the three clock-hands. 6. Press Esc to end the drawing mode. Stroke drawn 7. Use the Select tool to select the stroke and edit it as necessary. 3

4 Stroke selected 8. With the stroke is selected, click the Duplicate button in the General toolbar to make a copy of the stroke you just created. 9. Advance the clip forward by about one second. 10. From the toolbar, click Edit Shape and move the second stroke so that it passes through the second hand as shown here: The point where the two polyline strokes intersect is the center of the clock. You will use this as one of the points in the 2-point tracking. To make tracker placement easier, you will draw a dot over the two intersecting polylines. 11. Using the same brush properties as before, select the Freehand tool and draw a dot over the point where the strokes intersect as shown here: 4

5 Webtorials Avid DS Nitris Note: To see the intersection point more clearly, zoom in and use a larger brush size. 12. Select the two polyline strokes. Do not select the dot. 13. Deselect the Brush option in the Paint Style property editor. This hides the strokes which are no longer needed once you have found the center of the clock. Creating the Arrowhead You will now add the missing arrowhead to the clock hand. 1. Make sure you are at the beginning of the clip. 2. Add another Graphics effect to the clip. 3. Select Polyline as your Gfx Creation tool and set the properties as follows: - Paint Style: Fill > Use only - Fill Fx: Color > use the Pick tool to select the black color of the other clock-hands - Masks: RGB - Time Span: Start to End 4. Zoom in and draw a triangle-shaped polyline. Press the Ctrl key and click in the viewer to close the polyline. 5

6 5. Zoom back out and see if the arrowhead resembles the ones on the other clock hands. If you need to edit the arrowhead, select the stroke and click Edit Shape to adjust the control points. To make the arrow look like it is in motion, you will apply feathering to the arrow later in the lesson. Tracking the Shot Note: To improve the tracking process, always select a color that is absent from your image as the Color Space. This will produce a greater contrast. Since the arrowhead will undergo both translation and rotation, you need to use 2-point tracking. 1. With the arrowhead selected, click Tracker from the General toolbar. 2. In the Tracker property editor do the following: - Select 2-point for the Tracking Mode - Click Show to see the trackers - Select B (Blue) for Color Space to provide a better contrast between the dots and the green screen, as the screen contains very little blue 6

7 Webtorials Avid DS Nitris 3. Drag one of the trackers to the center dot of the clock. Note: The dot will not move during the tracking process, therefore the search area of the tracker can be very small. 4. Since you are using the white dot at the tip of the clock s hand to track with, hide the arrowhead temporarily by clicking Hide Gfx from the Tracker property editor. 5. Position the second tracker over the white dot on the clock hand as shown. Make sure the search area is quite large since the clock s hand will be moving quite quickly. 7

8 Track Forwards button 6. You are now ready to track. In the Tracker property editor, click the Track Forwards button. 7. Click OK in the dialog box that is displayed when the tracking is complete. 8. Click Show Gfx to see the arrowhead again. 9. Scrub through the clip and observe how the arrowhead is attached to the clock hand as it rotates about its center. Simulating Motion As you scrub through the clip, you may notice that the arrowhead is a bit too crisp and lacks a sense of movement. You can animate the feathering of the arrowhead over time so that it looks like it is in motion. 1. Make sure you are at the beginning of the clip and your arrowhead stroke is selected. 2. In the Paint Style property editor, set the Fill > Feathering Soft Radius to 2 and set a keyframe. 8

9 Webtorials Avid DS Nitris 3. Advance the clip forward about 10 frames to the point where the clock hand picks up speed. 4. In the Paint Style property editor, set the Fill > Feathering Soft Radius to 6 and set a keyframe. 5. Advance the clip forward another 25 frames to the point where the clock hand starts to slow down. 6. In the Paint Style property editor, set the Fill > Feathering Soft Radius to 2 and set a keyframe. 9

10 7. Scrub through your clip and notice how animating the feathering of the arrowhead stroke simulates blurred motion. Processing the Clip Before processing the final result, make sure you bypass the first graphics effect since you don t want the dot you created to appear. 1. Switch back to the Editing layout. 2. Bypass the first graphics effect you added by right-clicking on the clip and choosing Bypass from the menu. 3. Process the effect in frames. 4. Play back your clip to see the final result. 10