Tutorial 2: Adjusting Timing on a VirtualTrak set shot

In this tutorial we will walk you through how to set up and use the various “Trak” shots found within the ULTRA virtual set package. One of the biggest challenges is getting the timing correct for the start of the keyed clip, when the keyed talent becomes visible in the scene, and when they begin talking. As you’ll see in this tutorial, it’s actually very quick and easy.

In the Sessions tab, inside the Sample folder, you’ll find a session entitled Scene Timing Example. If you would like to compare your results, save your session and open this session.

Start a New Session.
Go to the Browse tab, and drag and drop the clip titled “Suzy – Wide – Walk in Left” into the Input Clip Icon.
Since the first frame of this clip is a good “clean plate,” click the Set Key button.
Fig 1: Initial Key

This particular clip has a lot of lights and light stands visible in the right side of the image. We need to clean this out of the image first by using the cropping tool. This is often referred to as “Garbage Matting” in the Chroma Key industry.
Go to the Input tab.
Find the Input Cropping window on the right side of the tab.
Grab the middle of the right side of the window, and drag it to the left until the light and other ‘garbage’ in the scene is removed. The number value for Right should be close to 164.25.
Fig 2: Cropping the Scene

You’ll notice a pretty hard edge in the “garbage matte” because of shadows in the background. This is exactly the situation the Edge Softness slider is used for.
Drag the Edge Softness slider all of the way to the right. You should see the hard edge at the cropping point disappear in the Output Preview Monitor.Now let’s get the VirtualTrak shot that we want.
Go to the Virtual Sets tab.
Double-click on the Museum folder.
Import the VirtualTrak Set shot entitled “Museum Intro” by dragging it and dropping it into the Virtual Set icon.
Play back the Output Preview Monitor.The goal we have here is to simulate Suzy walking out from behind the pillar as the motion in the scene comes to an end. Right now, Suzy walks out before we even see the pillar, and she is already talking before we even see her. We need to “slide” her clip forward, so she doesn’t start walking out until about 7 seconds into the shot.
Go to the Input tab.
Under the Output Preview Monitor, scrub to roughly 7 seconds into the scene. You should see the large pillar along the right side of the shot.
Under the Input tab, click the “Set” button for Offset Into Effect. This will offset the playback of the keyed clip until it starts becoming visible on the screen.
Scrub the preview again, and see if the timing looks right for Suzy to walk out from behind the pillar.
Fig 3: Choosing the Offset Point

TIP: You may want to try turning the keyer on and off while working on the timing of the scene. It can help to get the positioning right. You may want to trim some of the empty space off the head of the clip. There is about half a second at the beginning of the clip before Suzy actually walks out.
In the Source Preview Monitor, scrub the first second of the clip of Suzy. Look for the frame where Suzy’s foot first shows up. (It should be at about 15 frames into the clip.)
Click the Set button next to In Point in the Input tab.
Scrub the Preview clip again.Let’s quickly set up the keyer. We aren’t going to need to spend nearly as long adjusting the keyer this time compared to Tutorial 1, so quickly let’s revisit the process. We lit this clip to help match into the background, so we want to keep the long shadows in the scene while achieving a usable key around Suzy.
Lower the transparency slider, until Suzy is no longer transparent. You should have a setting around .365.
Play with the Alpha Curve and Start Threshold sliders, until the edging looks reasonably clean. Our Start Threshold is set for .600 and the Alpha Curve is set for .400.
Bring the Spill suppression all of the way to the right. (1.00)
Adjust the Desaturation until only the areas with green spill are being affected by the red spill suppression. In this image, the overall image has a lot of spill affecting the colors, so you’ll want the desaturation value fairly high. Our sample file has a value of .750.
Now, lower the Spill suppression back down until the “pink” in the image looks more natural. While the whole image has spill, you don’t need much to suppress it. A value around .225 should be sufficient.
No post-processing of the matte should be needed for this image.
Fig 4: Almost Done

At this point, you probably noticed that the clip of Suzy has a top-to-bottom line at the left edge that is interfering with the believability of the set. Lines on the edges of clips are a very common problem. Some cameras place a black matte around the active picture area to clean up noise in the edges. We could use the cropping tool, but that would affect where Suzy walked out from. It wouldn’t look like she walked out from the pillar – she’d be appearing from midair. Luckily, ULTRA has a setting to eliminate this problem.
In the Input Offset, set the X value to -0.02.Input offset keeps the positioning of video plane, but moves the image inside the plane. Setting the X offset to -.02 will slide Suzy’s image over to the left just a hair, but keep the positioning of the video plane lined up with the pillar.
Scrub the clip again to give a final check of the motion.
Fig 5: Final Shot

Now it’s time to save!