Join Steve Wright for an in-depth discussion in this video Tracking the sky matte, part of NUKE Compositing: Zombies.
- We're now ready to build our zombie graveyard which is going to be a day for night shot. We'll be using, of course, this background plate which has been waiting patiently for all of these videos. So let's open this guy up to show you that he's 100 frames long. So there's really the only camera move between one and 100, and then from 101 on, it's locked off because I wanted a locked off shot for the latter part. And of course, our zombie comes in at 105. So one of the problems with a day for night is the sky.
Watch what happens if I simulate a night grading. I'm going to darken this way down. Okay, no matter how much I darken it down, the sky looks silly bright, so we have to knock down the sky without disturbing any other part of the picture with a clamp. So let's undo this. I'm also going to need to mask it off so I don't clamp any other part of the picture, and I'm also going to have to track it because it's moving. The range of motion will be between frame 100, so let me set an outpoint here, and my picture stops moving, oops I accidentally moved my outpoint, so let me reset that.
Move the playhead and as we scrub towards the end, we run out of picture right about frame 61. So the sky is out of frame by 61, so I need to work between 61 and 100. Okay, we'll go to frame 100 because that's my last frame of motion. And I can draw my mask on frame 100. So let's type O to get a roto node. Come in here, and let's call this Gmat sky.
Back to the roto tab. Okay so I'm just going to do a quick and dirty here and then come back and polish it like so. Okay then we can cruise in. Now these are holes in the trees, so I've got to get them inside my mask so I don't have any shiny bits coming through. Okay, then get it above this stone, I don't want to clamp this stone. Alright, now we're going to be clamping these guys here along with the sky.
They are unimportant and we don't mind losing them. They would take a lot of trouble of tracking and keying and to try and save them, so we're going to sacrifice them as unnecessary. Okay so I'll bring this in here. Now I want to make sure I get rid of that guy, so I'm going to move that point there. And then these are two more holes in the trees, so I've got to make sure that they're inside my mat. Alright, tidy this up. And we are good to go.
Okay, next I'm going to need to track this from frame 100 back to frame 61. So for the tracking, of course, we'll need a tracker, select the Read node, hit the old tab key to get the pop-up list. I'll do a shift return on the tracker node so it's a branch connect. Hook my viewer up to the tracker node. And set it for the tracker tab. Now because there's some rotation in the camera movement, it's a steady cam, but there was a little bit of rotation in this move.
I'm going to need to do two-point tracking so I can track the rotation as well. So I'll make sure I'm on frame 100. Say I want to put a tracker here, and another tracker there. Turn off the trackers. Come back to these guys and tighten them up. I want to make them as big as I can because there's not a lot of texture on this stone, so I want to make these guys pretty darn big to grab a lot of pixels for happy tracking.
Okay, alright, so we got my two trackers. They're nice and big. Everybody's all set. I can now track backwards from 100 to 61, and by the way, if you're a little rusty on the tracker, you can review my Nuke essentials training course, chapter eight, tracking and stabilizing. So we're going to track backwards a limited range, so we want this guy here and we're going to go from frame 100 to 61, step minus one of course, click OK, and now we're tracking backwards.
And we're done. Okay, that looks good. Next, I'm going to set the transform to include both trackers for translation and rotation, but not for scale. The reason is, I don't need to do scale, and you never want to select something you don't need that can add drift to your tracking. We'll select the Transform tab, and there's my translate, rotate, and my center data, exactly what I'm looking for. Beautiful.
Okay, I'm going to jump the playhead to frame 100, because that's my reference, and this node is the tracker for the sky mat. Okay, next I need to link my tracker data to my Roto shape, and we'll see how to do that in the next video.
First you'll learn how to apply a quick key with Primatte, and enhance the zombie with realistic blood, red eyes, and fangs. Then, turning to the graveyard plate, you'll make a day-for-night color correction and add interactive lighting. Finally, you'll composite the key, plate, and effects and finalize the shot, using color correction and a push in effect. The process is broken down into easy-to-watch five-minute videos, rich in valuable VFX production techniques from compositing guru Steve Wright.
For more training on the basics, see NUKE Essential Training..
- Keying the zombie
- Adding a garbage matte
- Adding effects
- Turning a daytime shot into a nighttime graveyard
- Adding interactive lighting effects
- Compositing the zombie
- Applying final color correction