Friday, May 17, 2013

Rotoscoping Tutorial Part 2: Side Walk Cycle

For the second part of the tutorial, we will be examining how to rotoscope one direction of your walk cycle.  Probably the easiest one to do, the side walk cycle can still be tricky to get right.  Like anything else, it comes with practice, so don't feel frustrated if your results aren't perfect the first time.  I still have to do plenty of tweaking after the fact, as we will see below.

The first step is to film your model walking.  Ideally, you'll have a nice, clean studio, with a treadmill to walk upon.  Realistically, you'll probably have to do what I did and go for a walk in your back yard.  We'll start with the side view because you don't have to worry too much about resizing, like we will for the front and rear views.  Set your camera up on the tripod, keeping it about a height slightly lower than your chest, but making sure that there's plenty of space above and below the plane you'll be walking, so you stay within frame.

Once you've filmed yourself striding across camera, take your movie file and import it into a video editing program.  I use Adobe Premiere Pro CS5, but before that I was using regular old Premiere.  Find a section of your video where your model completes a full two step stride, then go back and go frame by frame, exporting the individual walk cycle frames.

In Adobe Premiere Pro, there is a handy "export frame" button right here.

 This depends on how many frames you want your walk cycle to be.  Rotoscoping will give you a smooth result, so my recommendation would be either 8 or 10 frames.  It really depends on how much animating you want to do.  For Ben Jordan I used 8, but for A Golden Wake I am using 10, so we will assume that this is the number you will be using too.  Once you select a point in your walk to start from, I suggest skipping ahead 4 frames to pick the subsequent ones.  This way, you'll have completed two steps by the time you hit 10.

Once you've got your 10 frames, it's time to open up your paint program and all of your frames.

Find the frame where the model's stride is the widest, then use the rectangle selector to crop it down.

Make sure the height of the box tops off at the top of the head and the bottom of the feet.  Next, move the box to the other frames so it maintains the same size, and continue cropping, until all 10 frames are the same size.

Now you can resize them all to sprite size and begin the tracing process.  At this point, you can always test to see that you've got a smooth animation.  Putting them all together gives me this:

As you can see it is slightly jerky, but that has more to do with the way the image was cropped, as it was more or less eyeballed.  This will be fixed for the final animation.

Next, as we did in part 1, we open up the files, but also our completed side view.  Copy the head from the side view onto the head of the walk cycle view for consistency, and also as a guide.

Now, we trace!  Every now and then, you should turn off your background layer to make sure your sprite is looking more or less proportionate.  As there is a lot of anti-aliasing happening because of the resize, it can be easy to make things a lot bulkier looking than they should be, for example the sleeves in this case.

 When you've finished tracing, erase the original image so only your sprite remains, and do any necessary cleanup of extra pixels .

Now, when you start on the next frame, paste the head in, and check to make sure it's in the exact same position as the frame you just drew.  In most versions of Photoshop, you can see this in the navigator window.

Check to make sure the head is aligned here.
 Doing this will avoid your sprite moving around jerkily in the final animation.  Continue this process for all the frames, keeping in mind that there is a head bob when people step.  Once you've finished, you should hopefully end up with something like this:

So there you have it.  Next time we'll deal with forward and backward walk cycles, which are just as easy, but involve a bit more prep work.

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