資料來源 : source_from BY CALEB WARD
After Effects is a fantastic tool for VFX work. This is especially true for motion tracking. However, the tracker you use to motion track your footage might not be the best choice depending on your specific clip. Let’s take a look at six different ways to execute motion tracking in After Effects and discuss when certain tracking features should and shouldn’t be used.
在VFX工作中，AE是一個夢幻工具，特別對Motion tracking的確如此。然而，你選的追蹤方式不一定對你的特定片段是最好的。我們看看在6種不一樣方式，在AE裡執行motion tracking並討論當主要追蹤功能應該和不應該被使用。
1. One Point Track 單點追蹤
When to Use It: Very quick 2D tracking situations centered around a single point with no warping.
使用時機 : 非常快速2D移動情況,中心環繞一個點，並且沒有包覆到。
The single-point tracker built into After Effects has long been a go-to tool for motion artists, but you need to be careful with single-point tracks because footage doesn’t normally shake in 2D space only. After Effects uses contrast to find track points, so you’ll need to make sure you set your tracker on a well-defined point. If you’re in a rush, one-point tracking will work, but for most professional circumstances, you’ll want to at least use two-point tracking.
單點Tracker，內建在AE裡對動態藝術家已經是一個長期協助的工具，但你需要小心注意，使用單點Tracker，因為素材不會只在2D空間正常的晃動。AE使用對比找出track point，所以你將需要確定你設的tracker在容易定義的點上。如果你很急迫，單點追蹤也能使用，但對大多專業分工的情況下，你會希望至少使用兩點追蹤。
In this tutorial from Live Tech Australia, we take a look at how to use the single-point tracker in After Effects.
這個教學來自Live Tech Australia，我們來看如何在AE使用單點Tracker。
2. Two Point Track 2點追蹤
When to Use It: On footage with mild to moderate levels of camera shake.
使用時機 : 當素材有輕度到中度程度的攝影機晃動。
Two-point tracking is fantastic for simple camera movements, as long as there are a few contrasted elements for the tracker to track. Two-point tracking is notably superior to single-point tracking because it can track rotation and scale, not just position.
2點追縱對單純的攝影機移動是奇妙的，只要有一些對比的物件讓tracker可以追蹤。2點追蹤比單點追蹤更好，因為它可以追旋轉和縮放，不只是位移而已。
This video from Robert’s Productions shows us how to use two-point tracking to add text to a scene.
這支影片來自Robert’s Productions，將告訴我們如何使用2點追蹤在場景增加文字。
3. Corner Pin Track 邊角追蹤
When to Use It: Basic screen replacement.
使用時機 : 基本的螢幕置換
If you do a lot of commercial or sci-fi work, then you probably do a lot of screen replacements. In order to help make screen replacements easier, After Effects has a built-in corner pin tracker that is designed to work with any four point surface. While it’s designed to work with screens, it can also work with picture frames, signs, and simple surfaces. In this video tutorial from LinkTCOne, we take a look at how to use the corner pin tracker to replace a picture frame inAfter Effects.
如果你是做很多商業類或科幻類的作品，那麼你可能會做到很多螢幕置換。為了要讓螢幕置換更容易，AE已有內建corner pin tracker,被設計處理任何4點的表面。當它被設計來處理螢幕，它也可以處理照片，標誌，和單純表面。在此教學(原教學已失聯)，我們看看Corner pin tracker 如何在AE替換影像。
如果你是做很多商業類或科幻類的作品，那麼你可能會做到很多螢幕置換。為了要讓螢幕置換更容易，AE已有內建corner pin tracker,被設計處理任何4點的表面。當它被設計來處理螢幕，它也可以處理照片，標誌，和單純表面。在此教學(原教學已失聯)，我們看看Corner pin tracker 如何在AE替換影像。
4. 3D Camera Tracking 3D 攝影機追蹤
When to Use It: Matte painting, set extensions, and compositing.
使用時機: 遮罩繪畫，設置擴展，和合成
One of the most powerful features to hit After Effects in recent years is the 3D camera-tracking tool. The tool essentially automatically creates dozens of track points in your footage and allows you to select which ones to use after the computer processes the footage. This is your best tracking option directly in After Effects. However, the 3D camera tracker can take quite a while if you have a long clip.
近幾年來，在AE裡最強大火紅的功能，就是3D camera tracking工具。在電腦計算處理過素材後，這工具基本上，在你的素材中自動製造出數個追蹤點，並允許你選擇其一來利用。這是你在AE中最好的追蹤選項，然而如果你有較長的片段，3D camera tracker 會花你較多時間。
This tutorial from thevfxbro shows us how to use the 3D camera tracker to ‘composite’ a Christmas tree into a shot.
這個來自thefxbro將展示如何使用3D camera tracker 在一顆鏡頭合成一顆聖誕樹。
5. Planar Tracking Using Mocha 使用Mocha平面追蹤
When to Use It: Advanced tracking on flat surfaces.
使用時機 : 在平面上更進階追蹤
If you have a very difficult-to-track flat surface, then the planar tracking feature in mocha Pro is the way to go. Unlike After Effects, mocha Pro will use predictive tracking to track the position of an object even if a portion of the tracked object is off screen. Tracking data can then be exported from mocha into After Effects.
如果你有一個非常難去追蹤的平面，那麼在Mocha Pro的平面追蹤的功能是不錯的選擇。不像AE，mocha Pro 使用預測追蹤一個物體位置，即使追蹤物件的部分是在螢幕外。Tracking data可以從Mocha 匯入AE。
This quick video tutorial from short-form video shows us how to planar track in mocha.
這個來自short-form video，將告訴我們如何使用平面追蹤
6. Spline Tracking 曲線追蹤
When to Use It: Complex camera tracking jobs.
使用時機 : 複雜的攝影機追蹤工作
If you’ve exhausted all of the other options on this list, or simply want the most accurate track possible, then spline tracking in mocha Pro is the way to go. Spline tracking can track any type of shape because you custom create the tracking plane. Essentially, you trace around the object you want to track and mocha will try its best to keep track of the object. Data can then be exported to After Effects.
如果你對這列表感到困惑，或只是想更精確的追蹤，那麼在mocha pro的曲線追蹤是好選擇。曲線追蹤可以追蹤任何形狀，因為你可以自製追蹤形狀。基本上，你可以追你想要物件，而mocha會試著追出最好的資料，資料也可以給AE
This tutorial from mocha planar tracking & vfx tools shows us how to use spline trackers to do beauty retouching inAfter Effects.
這個教學，mocha planar tracking & vfx tools 將告訴我們如何使用曲線追蹤
