Chrono::Engine is a part of Project Chrono. It is a library for physical simulation of complex mechanisms with parts, constraints, contacts and collisions.

Code Quality Rank: L1
Programming language: C++
License: BSD 3-clause "New" or "Revised" License
Latest version: v5.0.1

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Project CHRONO

pipeline status BSD License

Project Chrono represents a community effort aimed at producing a physics-based modelling and simulation infrastructure based on a platform-independent, open-source design. The name of this software infrastructure is Chrono. Some of its features are listed below. The applications areas in which Chrono is most often used are vehicle dynamics, robotics, and machine design. In vehicle dynamics, Chrono has mature support for tire/terrain interaction modeling and simulation.


Physics modeling

  • Rigid body support
  • Flexible body support - both for ANCF and co-rotational nonlinear finite element analysis
  • Support for fluid-solid interaction problems, via Chrono::FSI module
  • Coulomb friction model capturing stick-slip phenomena.
  • Support for rolling friction and spinning friction.
  • Support for handling frictional contact via two approaches: a complementarity approach and a penalty approach.
  • Springs and dampers with non-linear response. Can be user defined.
  • Large collection of joints and constraints: spherical, revolute, prismatic, universal, glyph, screw, bevel and spur gears, pulleys, etc.
  • Unilateral constraints.
  • Constraints to impose trajectories, or to force motion on splines, curves, surfaces, etc.
  • Constraints can have limits (ex. elbow).
  • Constraints can be rheonomic or holonomic
  • Custom constraint for linear motors.
  • Custom constraint for pneumatic cylinders.
  • Custom constraint for motors, with reducers, learning mode, etc.
  • On the fly constraint activation/deactivation.
  • Simplified 1D dynamic models. Examples: powertrain, clutches, brakes, etc. For more sophisticated models see companion Chrono::Vehicle module.
  • All physical items can have an arbitrary number of 'assets' used for defining visualization shapes, custom properties, etc.


  • HHT solver for index 3 differential algebraic equations.
  • Symplectic first order half-implicit Euler solver for large frictional contact problems.
  • Speed-impulse level solver for handling large frictional contact problems.
  • Handling of redundant/ill posed constraints.
  • Stabilization or projection methods to avoid constraint drifting.
  • Static analysis solver.
  • Inverse kinematics and interactive manipulation.

Collision detection features

  • Supports compounds of spheres, cubes, convex geometries, triangle meshes, etc.
  • Additional collision support provided by the Bullet collision detection engine, which is wrapped inside Chrono::Engine.
  • Broad phase collision detection: sweep-and-prune SAT.
  • Narrow phase collision detection: AABB and/or OBB binary volume trees, to handle geometries with thousands of details.
  • Detail phase with custom primitive-to-primitive fallbacks.
  • Safety 'envelope' around objects.
  • Report penetration depth, distance, etc.
  • Bodies can be activated/deactivated, and can selectively enter collision detection.

Implementation details

  • ANSI-compliant C++ syntax.
  • Optimized custom classes for vectors, quaternions, matrices.
  • Optimized custom classes for coordinate systems and coordinate transformations, featuring a custom compact algebra via operator overloading.
  • All operations on points/speeds/accelerations are based on quaternion algebra and have been profiled for fastest execution.
  • Custom sparse matrix class.
  • Custom redirectable stream classes, featuring platform independent file archiving and modern syntax.
  • Special archive engine, with easy and reliable persistent/transient serialization. Includes versioning and deep pointers storage.
  • Expandable run-time class factory.
  • Custom pseudo-'run-time-type-information', to allow persistence even in case of name-mangling with different C++ compilers.
  • High resolution timer, platform independent.
  • Class to create PostScript(tm) output.


  • Interface with MATLAB
  • Cosimulation with Simulink
  • Import STEP cad files to define complex geometries
  • Online/offline visualization with Irrlicht and POV-Ray, respectively.
  • Classes for genetic & classical optimization.
  • Classes for interfacing external geometric data (NURBS, splines).
  • Scripting via Python.
  • Makefile system based on CMake (cross-platform, on Windows 32/64 bit, Linux, OSX).

*Note that all licence references and agreements mentioned in the CHRONO README section above are relevant to that project's source code only.