Motion Capture Recording

1 Powering On The System
2 Starting Motive
- 2.1 Starting a Session
3 Motive Modes and Controls
4 Camera Calibration
- 4.1 Masking Visible Reflections
- 4.2 Full Camera Calibration
5 Suit and Skeleton Calibration
- 5.1 Showing and Hiding Skeletons and Recalibration
6 Recording
7 Exporting .fbx Files

Please see https://rhodescollege.atlassian.net/wiki/spaces/HPCL/pages/3395059720 before your first visit. In addition to the quick-start guide below, a review of the officialhttps://docs.optitrack.com/v2.3/motive/motive-basics is recommended.

Powering On The System

The main power for the motion capture cameras and desktop is located in the equipment closet next to the desktop. The orange power switch on the bottom rack-mounted power distribution unit (PDU) needs to be flipped on. Please make sure the desktop computer is fully shut down before turning off the PDU when lab use is complete.

Power switch location on rack-mounted PDU

Starting Motive

Shortcuts to open Motive can be found in the taskbar and on the desktop of the Motion Capture desktop:

OptiTrack Desktop Icon

OptiTrack Taskbar Icon

Starting a Session

Motive stores working data in Session folders. On launch Motive will automatically open the most recently active session. If no session is found (e.g. the folder was moved or deleted) then a new session will be created by default in C:\Users\OptiTrack\Documents\OptiTrack with the name Session [YYYY-MM-DD].

To review or edit open sessions open the Data Pane in the View menu:

View Menu > Data Pane

To open a previous session select Add Session Folder from the File menu or click the small plus sign in the bottom left of the Data Pane.

File Menu > Add Session Folder

Motive Modes and Controls

Work in Motive is done in either the Live or Edit modes. Live mode shows the current state of the system and is used for controlling the recording process. Edit mode is for reviewing and editing recorded takes. You can switch modes using the buttons in the bottom left of the interface, or by clicking the cyan mode label at top of the main Perspective View Pane:

Mode select buttons

Mode in perspective view

In the Perspective View Pane the orange label indicates the type of markers the cameras are monitoring. We are using Passive markers with our current suit setup. If this button accidentally gets clicked it can also read as Active or Active + Passive. Clicking it again should return it back to Passive.

Mouse controls in both modes are:

Function	Default Control

Function	Default Control
Rotate view	Right + Drag
Pan view	Middle (wheel) click + drag
Zoom in/out	Mouse Wheel
Select in View	Left mouse click
Toggle Selection in View	CTRL + left mouse click

Useful hotkeys can also be found in https://docs.optitrack.com/v2.3/motive/motive-basics#basic-navigation-controls.

Camera Calibration

Below is a quick-start guide to calibrating Motive. Further details can be found in the official documentation linked at the beginning of each section, such as: https://docs.optitrack.com/v2.3/motive/calibrationand OptiTrack Motive - Volume setup and calibration.

Masking Visible Reflections

If cameras have been recently calibrated then the only step needed is to mask visible reflections. In the Camera Calibration Pane click Clear Mask and then Mask Visible.

Calibration Masking Controls

After clearing the mask any visible reflections will show as white dots or lines in the Camera Preview pane. After clicking Mask Visible hidden reflections will turn red and will be ignored during tracking.

Camera preview with mask cleared

Camera preview with mask applied

Full Camera Calibration

Full calibration should only be needed if cameras have been moved or the system has not been used for a while. An older camera calibration procedure is transcribed below. An updated version will be added soon.

Take the two brown boxes on the top shelf of the closet down. You need the longer box first. [No longer relevant]
Remove the pieces inside the box + follow the assembly instructions printed on the left side. [No longer relevant - calibration equipment is assembled and on the table in front of the lab podium]
On the computer, open Motive + choose "Perform Camera Calibration" from the quick start menu that pops up.
Remove all markers and other objects from the space. Use the curtains to block out reflective surfaces if possible.
In the Calibration pane, Click "Clear Mask" followed by "Mask Visible". Now, click the orange box at the top until it reads "Passive" (NOT "Active + Passive")
Turn on the wand you assembled in Step 2, and have someone click "Start Wanding" (if alone, click start wanding first).
Walk around the space, waving and tilting the wand. The LED ring around the cameras will track your movement - use this visual indicator to make every camera's light a solid green color. After this is done, turn off the wand. Each camera needs between 1k + 10k samples.
1. going above 10k samples on a camera actually reduces quality, so try not to spend too long on a single camera.
When done, click "Calculate". When it says "ready to apply", click apply IF the overall result is "exceptional".
Open the smaller brown box, take out the tool and place its corner vertex on the blue tape X in the middle of the room. Short side should point to the doors, longer side towards the platform. Turn it on (battery tape side up).
This sets the '"+X" + "+Z" directions of the ground plane, so try to get it as close as possible to parallel with the walls.
Highlight the three orange markers on the screen by left-clicking + dragging - they should turn yellow. Then click "Set Ground Plane" to complete the calibration. Don't change any of the numbers!
Save the calibration file when the pop-up appears.
Of note- every active camera will be calibrated, unless turned off in advance, including the small color camera pointed straight at the ground in the south-west quadrant of the room. Unless it's off, YOU MUST WAVE THE WAND UNDER THIS ONE! You will not be able to apply the results or finish calibrating unless every camera has at least 1K Samples.

Suit and Skeleton Calibration

https://docs.optitrack.com/v2.3/motive/skeleton-tracking

For a new session with no skeletons calibrated begin by opening the Builder Pane from the View menu:

View Menu > Builder Pane

At the bottom of the Builder Pane select the Skeletons option:

Currently our suits are marked using the Baseline (37) Marker Set. See the https://rhodescollege.atlassian.net/wiki/spaces/HPCL/pages/3156344835/Motion+Capture+Lab#Mocap-Suit-Inventoryfor more details. The other settings in use are:

Pose: T-Pose
Labels: Default
Name: Anything you'd like, we have used S, L, and XL for the three suits currently in use.

You can use right-click and middle-click to rotate and move the skeleton if you need to check marker positioning on the suits. White markers should always be placed exactly where shown in the model. Magenta markers have more flexibility for the placement location but the location should still align relatively with other magenta markers in the same area (e.g. the left thigh marker should be placed higher than the right thigh marker, as shown above). Further details can be found in the segment marker section of the https://docs.optitrack.com/v2.3/motive/skeleton-tracking#segment-markers .

An actor will now need to put on whichever suit is being calibrated and stand in a T-Pose in the capture area with no other markers visible to the camera. The Markers Detected readout on the left side of the Builder Pane should read 37 matching the Markers Required on the right.

A lower marker number can sometimes occur if markers are obscured or in the incorrect place (ankles can be tricky depending on how the shoes fit). A higher number may occur if new reflections have appeared since initial masking, or if some markers are accidentally left in view of the cameras.

Review the actor model in the Perspective View Pane and if things look good, click Create. The suit and skeleton are now calibrated.

Calibrated skeleton in T-Pose

Showing and Hiding Skeletons and Recalibration

If multiple skeletons have been calibrated you can manage each skeleton from the Assets Pane in the View menu:

View Menu > Assets Pane

The left-hand checkboxes in the Assets Pane will enable or disable each skeleton for viewing or recording. If markers are moved at any point, or the suits fit differently on multiple people, Recalibrate From Markers is available by right-clicking an entry in the Assets Pane.

Recording

https://docs.optitrack.com/v2.3/motive/data-recording

In Live mode recording is done using the Control Deck at the bottom of the Motive interface.

For each recording specify a Take Name to the left of the mode selection buttons:

Take Name location in Control Deck

Motive will automatically append an incrementing number after the specified name (i.e. _001, _002...) when multiple take are done in a row.

You are now all set to record using the red button in the middle of the Control Deck area. Clicking the same button will end a take. Starting and ending in a standing T pose may be useful as a baseline when using the motion capture data in other programs.

Exporting .fbx Files

Motion capture data exported to fbx format can be used in a variety of other animation and modeling programs. An export can be done by going to Export Tracking Data in the File menu.

File > Export Tracking Data

In Files of type select FBX Binary Formatunless you know you need FBX ASCII Format instead:

We have used the defaults listed above to export to .fbx and import skeletons into Blender along with recorded motion capture animation:

Motion capture skeleton as it appears in Blender after .fbx import