Knowledge Base

1 Introduction

1 Introduction

What Is Track3d?

Track3D 2.0 is an add-on to the EthoVision XT software for automated tracking of animals in a 3D space. It allows you to visualize the trajectory of the animal in a three-dimensional picture, and calculate a wide range of movement variables such as velocity and turn angles in the 3D space.

How Does Track3d Work?

As you may already know, the EthoVision XT software records the position and movement of an animal in a 2D space by analyzing the images coming from a video camera or a pre-recorded video. In order to analyze the movement of animals in 3D space, two video cameras are needed. EthoVision XT tracks the animal's body center from both Figure 1 Example of 3D flight trajectory of a mosquito. Circles represent the odour plume. 1 Introduction camera views. This results in two sets of coordinates, each in a 2D space. The Track3D software combines the EthoVision track data from the two camera views. This software includes CentroidFinder, to calibrate the video image and obtain an accurate representation of the 3D world projected on two dimensions, and Track3D, which does the job of transforming the two sets of 2D coordinates into one set of 3D coordinates (X,Y,Z). Track3D also visualizes the trajectory of the animal in a 3D space, and quantifies the animal's movement by calculating a number of variables.

Step 1 - Recording video

Aim - To provide video footage that EthoVision uses to track the animal and record the 2D coordinates. Video is recorded from the two cameras simultaneously and is saved to full resolution video files. How? - With EthoVision XT or MediaRecorder. See page 44 Figure 2 Main steps in the Track3D workflow. 1 Introduction

Step 2 - Acquiring the tracks

Aim - To provide sets of coordinates of the animal's body center in a 2D space. How? - With EthoVision XT. See page 48, page 54, page 58

Step 3 - Visualizing and analyzing 3D tracks

Aim - To obtain a 3D representation of the animal's trajectory and calculate 3D movement variables (e.g. speed, heading). How? - With Track3D. See page 59

Calibration

Aim - To determine the relationship between the 3D coordinates in the real world and their projection on the 2D space of the video image that is used by EthoVision to track the animal. You can obtain reliable 3D data only if you carry out an accurate calibration. How? See page 26. You do not need to calibrate every time you acquire data. A new calibration is needed when the camera position changes relative to the tracking chamber. If the cameras and the tracking chamber are fixed, you can always work with the same calibration.

Track3d Software Components

MediaRecorder

It includes an encoder board to be installed on your PC and special software that records video from multiple cameras to high-quality video files. Recording starts at the same time for all cameras, so the images recorded are synchronized. 1 Introduction

EthoVision XT

Software for video-tracking. In EthoVision XT, you track the subject from the video files recorded with MediaRecorder. First, you define in which area of each camera view the subject is going to be (arena). Next, you instruct EthoVision on how to distinguish the subject from the background, and start data acquisition.

Calibration software: CentroidFinder

In order to calculate movement variables in 3D units (e.g. 3D flight path) one needs to transform the original tracking data (obtained from 2D images) to 3D coordinates. This transformation is only possible if the relationship between the position of specific points (called calibration markers) in the real world and their projection on the video image is known. The calibration software helps you assessing this relationship from a static picture of the calibration markers.

Visualization and Analysis software: Track3D

The program for visualizing the tracking data. This program has two inputs (1) the calibration file obtained from the calibration software and (2) the input data file with the 2D data that you create from the two tracking data sets (one per video camera). In order to use CentroidFinder and Track3D, you need to install a Matlab Component Runtime library. If this is not installed on your PC, you can find it on the installation disk. Copy the file MCRInstaller.exe to the folder C:\MCR, and double-click it. Follow the instructions on the screen and make sure that you install the library on C:\MCR.

What's New In Track3d 2.0

Software license key

In order to run Track3D and CentroidFinder, you must have your EthoVision XT hardware key plugged in your computer. Note that you do not have to install EthoVision XT and Track3D on the same computer. You can have them on two different computers. However, make sure that the computer on which Track3D is installed 1 Introduction has the drivers for the hardware key correctly installed. You can find these drivers on the EthoVision XT installation DVD.

Importing EthoVision XT track files

You no longer have to combine the track files for camera 1 and camera 2. Track3D does that for you.

Definition of 3D zones

You can split your tracking chamber in several three-dimensional zones, cuboids or cylinders. Track3D marks each data point in the results file based on the point's position in one of those zones. You can then filter the data of the results file with Excel to analyze data points in a zone or a combination of zones. See page 67 for definition and page 116 for analysis.

Creating a video of your 3D track

After opening the 3D track chart, you can let Track3D capture part of your computer screen while the track is being played back. Track3D saves this video as an AVI file. For more information, see page 82.

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Source: Track3D 2 - Reference Manual (March 2025)