OK, now we’re getting into the fun stuff! But, with over 2 minutes of animation and 60 shots left create (including putting lots of props into hands) we’re going to need a faster and easier ways to do things.
In this MotionBuilder tutorial I’ll show you how you can quickly build scenes using the power of MotionBuilder Python Scripts, create slow motion effects in Story Tool, and instantly align props in hands using Character Extensions.
The idea is to show you some of the tools and techniques you might use if you were working on complex mocap sequences like this for a film or video game.
Python Scripting
In one of the first videos we put together the opening sequence of the lobby shoot out, manually merging characters, environments, props and then adding reference cameras and shot cameras, which took us a while.
Now, this is fine if you’re just working on your own and you only have one shot to do, but if you’re working on a big project with lots of scenes to build and lots of people working on them, then you’re going to need a faster and easier way to do this. And this is where MotionBuilder Python comes to the rescue.
In this example I’ll show you how I use Python to open a master scene file, merge in characters and props, add them to a namespace, create a Character Extension, add the prop into the Character Extension, and finally add all the character in to Story Tool ready to recive all our lovely mocap.
Not only does this save you time, but it also means it’s done in exactly the same way on every shot, scene and sequence we will build. Rather than having to do multiple clicks, file opens and merges, and hoping you don’t forget anything, the script will do everything automagically. This means anyone can build a shot without any experince of this kind of work (or MotionBuilder, really), and it will be done in exactly the same way, every time. This means anyone working on a scene will know how it works and where everything is.
To speed things up even more, there’s also another handy script that creates our shot cameras (the cameras we are rendering from) and our refereence camera showing the video playback in. What took time and faffing the first time round, can now be done in a second with a single click.
Resampling Mocap for Slow Motion Effects
Normally on a mocap project there are 2 different frame rates: Capture Frame Rate and Delivery Frame Rate.
Capture Frame Rate is the frame rate or frames per second (FPS) the data was captured at. For this project we’re using and MVN system with captures at 240fps.
Delivery Frame Rate is the frame rate the final data is going to be worked on. This is usually the frame rate the data will be rendered. For example, in video games this could be 30fps or for film and VFX this could be 24fps.
Another time the delivery frame rate might change is when we need to change the speed of the motion capture action to create a slow motion (slo-mo) effect.
To create a slo-mo effect you need to scale the speed of the motion capture to increase the number of frames or time it takes for the action to happen. So, rather than taking 1 second to complete, it could take 2, 5 or even 10 seconds to complete. When you do this kind of work, you need to make sure you don’t resample your original mocap data too much so you lose all that lovely detailed mocap you captured at 240 fps.
Always check if your mocap will need slowing down before you decide on your delivery frame rate. This way you can get it delivered at a higher frame rate so when you slow it down you will be able to see all that subtle detail you captured in the orginal action.
Rescaling Clips in Story Tool
To create the slow motion effect in our scene, we’re going to be scaling our clips using Story Tool.
There are a couple of different ways you can rescale a clip in Story:
- Manually, by dragging the start or end of the clip in Story Tool to change the speed of the action.
- In the “Asset Settings” for the clip, you can set the “Speed” if you know the values you want to match to
- Or you can also change the “Speed” of the clip in the “Properties” tab.
MotionBuilder Character Extensions
Character Extansion can be used to connect an object to a character’s Control Rig. This means the Character Extension object will be included in any Full Body key frames you set or Poses you create.
To help us out here, we’ll be taking advantage of this by creating poses from the shots where we’ve already fixed the alignment of the props in the characters hands. This means we’ll be able to fix a lot of the remaing shots where the characters are holding weapons with a single click, saving us a lot of time.
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