Polychase

A free and open-source motion tracking addon for Blender, inspired by KeenTools GeoTracker.

Overview

Polychase is a 3D motion tracking solution that allows you to track camera movement or object motion in video footage within Blender. It uses optical flow analysis and PnP, aided by user input to provide accurate tracking results.

Features

Core Tracking Capabilities

• 3D Pin Mode: Place and manage tracking pins on 3D geometry
• Camera/Geometry Tracking: Track camera/geometry movement through 3D space
• Trajectory Refinement: Refine tracking results using bundle adjustment

Advanced Features

• Variable Camera Parameters: Support for estimating focal length and principal point
• Keyframe Management: Complete keyframe control for tracked animation
• Scene Transformation: Transform entire tracked scenes
• Animation Conversion: Convert between camera and object tracking
• Real-time Preview: Live tracking progress and results
• Mask Support: 3D masking for selective tracking

User Interface

• Integrated Blender UI: Native Blender panels and operators
• Visual Feedback: Color-coded pins, wireframes, and progress indicators
• Customizable Appearance: Adjustable pin colors, sizes, and wireframe styles

Usage

Basic Workflow

1. Setup Scene:

   • Import your video footage as a movie clip
   • Add or import the 3D geometry you want to track
   • Set up a camera object

2. Create Tracker:

   • Open the Polychase panel in Blender's 3D viewport
   • Create a new tracker
   • Assign your clip, geometry, and camera

3. Analyze Video:

   • Set the database path for optical flow storage
   • Run "Analyze Video" to generate optical flow data

4. Pin Mode:

   • Enter pin mode to place tracking points on your 3D geometry
   • Add pins by clicking on the geometry surface
   • Drag the pins to adjust the pose of the geometry/camera

5. Track Sequence:

   • Choose tracking direction (forward/backward)
   • Select tracking target (camera or geometry)
   • Run tracking to generate keyframes

6. Refine Results:

   • Use the refine sequence tool to improve tracking accuracy

Pin Mode Controls

• Left Click: Add new pin
• Right Click: Delete pin
• M: Go to mask drawing mode
• ESC: Exit pin mode

Technical Details

Architecture

• C++ Core: High-performance tracking algorithms written in C++
• Python Bindings: pybind11 integration for Blender compatibility
• Blender Integration: Native Blender addon with custom operators and panels

Algorithms

• Optical Flow: Off-the-shelf OpenCV solution
• 3D Tracking: PnP (Perspective-n-Point) solving for camera pose estimation
• Bundle Adjustment: Global non-linear optimization for trajectory refinement
• Ray Casting: Accelerated mesh intersection using Embree

Demo & Technical Walkthrough