SCA2020: Linear Time Stable PD Controllers for Physics-based Character Animation

project page, paper, demo, talk

Introduction

This is the accompanying code for our SCA2020 paper. To reproduce the reported results, a patch to simulation engine (here we use PhysX) is required. The patch is included in this repository and see below instructions for how to apply it to PhysX simulator. The main part of this repository is a test environment to compare different SPD algorithms.

Test system

Our tests are performed on Archlinux. CMake is used to build the system. The system should generally work on other linux systems as well. On Windows there are some dependency issues.

PhysX setup

• Clone official repo from github. Make sure the version is 4.1.1.27006925. Since PhysX usually change low level code during upgrades, other versions will most likely not work.
• Apply MABA-on-PhysX4.1.1.27006925.patch
• Follow PhysX build instructions to build binary files and install headers. After this procedure, you should have ---/PhysX/physx/bin/linux.clang/release and ---/PhysX/physx/install/linux

Simulation rendering setup

By default, a built-in renderer is used which is ugly. Press Space key to start simulation and use mouse drag and WASD to adjust view port. No other setup is required if you use this renderer.

If you would like to achieve the rendering effect in the paper or video, please first set up the Unity renderer. Detailed documentation and tutorials are available. Then enable ENABLE_UNITY_KINEMATICS CMake option when configuring this project. Search for UR_Init in the code to change IP address and port required by Unity renderer (if needed).

Build

First create a folder named build, then please use cmake-gui to build this project. We have included hints for how to configure this project. You will need to specify PhysX binary and installation path, Eigen path. You can basically leave other options as default.

• Enable ENABLE_UNITY_KINEMATICS to use Unity renderer.
• Enable BUILD_API to get a simple python binding of PhysX character simulation.

Run the SPD tests

In the build folder:

Quasi-physics tracking:

./poseTracking -m run.txt

• -m [mocap_file]. Mocap files are in resources folder.
• Use -c 0/1/2/3 option to specify SPD controller. 0 is MABA, 1 is sparse LLT, 2 is dense LLT (traditional), 3 is kinematic (for debugging).
• Use --dog to use the dog model.
• Use -N [x] to specify number of characters, use --column to specify number of columns to arrange these characters.
• Use -t [x] to specify simulation time step.
• Use -p to measure performance (no rendering).

Snake

./snake -L 48

• Use -L [x] to specify snake length

Other notes

• SPD components are in src/articulations/spd folder, jump here if you just need to look at the code.