Brief Introduction

The following is a short list of main attributes of Chrono.

Physics modeling

  • Rigid body support
  • Flexible body support via Chrono::FEA module - 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

  • C++ syntax (requires C++11)
  • 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.


  • Template-based vehicle modeling through Chrono::Vehicle
  • Scripting via Python (Chrono::Python)
  • Interface with MATLAB (Chrono::Matlab)
  • Cosimulation with Simulink (Chrono::Cosimulation)
  • Import STEP cad files to define complex geometries
  • Online/offline visualization with Irrlicht and POV-Ray, respectively.
  • Classes for interfacing external geometric data (NURBS, splines).
  • Build system based on CMake (cross-platform, on Windows 64 bit, Linux, OSX).