Getting started with multiple actors

Introduction

Starting from version 2.4, iPi Mocap Studio supports multi-person tracking with the following limitations:

• Currently only two actors tracking is available in the public release.
  • Tracking of more than two actors requires more RnD and currently not feasible due to mutual occlusion of actors.
• At least 5 Sony PlayStation Eye cameras are required to track multiple actors.
• It's recommended to use 6 — 8 cameras to track multiple actors.
• For simple actions when actors are rarely close to each other you can use 4 — 5 Sony PlayStation Eye cameras or even two depth sensors (MS Kinect / ASUS Xtion / PrimeSense Carmine).
• For single depth sensor and for 3 web cameras multi-person tracking is not enabled.
• Multi-person tracking is available only in STANDARD edition. In other editions you can try this functionality but in this case all results will be saved in restricted trial format which prohibits export of result animation.

Actors Clothing

For color cameras:

• All regular recommendations.
• Plus it's highly recommended to use different colors for clothing of different actors. It will minimize tracking errors.

For depth sensors:

• Only regular recommendations. No additional recommendations, because current version of iPi Mocap Studio doesn't use color data from depth sensors during tracking (color data is used only for visualization).

Cameras Configuration

The main requirement is to minimize self- and mutual occlusions of actors. In general, 5 — 8 cameras should be placed in full-circle with at least two cameras at 2.5+ meters height. If you're going to use less cameras then all actions should be planned in such a way which minimize mutual actors occlusion. For example, screenshot below demonstrates how to capture two actors handshake with just two depth sensors:

Scene Configuration Example

T-pose

It's convenient but not strongly required when both actors stay in T-pose at one and the same time as far from each other as possible (but both actors should be fully visible in all cameras).

T-poses of Actors

Processing

• During project creation you will need to specify number of actors and then parameters of each actor:

How many actors?

First actor parameters

Second actor parameters

• At the toolbar you will see buttons for switching between actors. Also you can switch by clicking on actor model in the 3D view port. Skin of "inactive" actor is grayed. Content of Actor tab is displayed for the active actor.

Active actor on UI

• For each actor:
  1. Roughly align actor's model with actor's images in all cameras using Move, Rotation and IK tools
  2. Adjust actor parameters if needed
  3. Click Analyze Actor Appearance button
  4. Correct actor's colors with the aid of Eye dropper if needed
  5. Click Refit Pose on Tracking tab.

     Note. Unlike all other content of Tracking tab this button runs refit pose for active actor only and doesn't affect the inactive one

  6. Repeat steps starting from 3 if needed

• Adjust Region-of-Interest, choose tracking settings on the Tracking tab and execute tracking

  Note. All options and action buttons on the Tracking tab except Refit Pose button are applied to all actors.

Tracking Tab Controls

• After processing you can use regular procedures for clean-up and post-processing.

Motion Controllers

You can use up to 6 motion controllers for:

• left hand of the first actor
• right hand of the first actor
• head of the first actor
• left hand of the second actor
• right hand of the second actor
• head of the second actor

Or any subset of these items.

For projects with two actors you will be able to choose both body part and actor index in the Attach to drop-down list on Motion Controllers tab:

Attach to drop-down list

Animation Export

Using Import target character on Export tab you can import target character for active actor. If you want to import target character for the second actor, just make it active using buttons on toolbar and repeat import. Target characters can be the same or different.

In a similar way, Export animation button works for active actor. That is you can export animation for each actor separately. Current version of iPi Mocap Studio doesn't allow to export animation for both characters to the one output file.

Export