A simple, performant and accurate physics engine implemented in pure Julia using ModelingToolkit.jl and DifferentialEquations.jl. Depends on PrimitiveCollisions.jl for collisions. To use:

] add Collide 

A simple world with 2 rectangular entities, and no gravity:

using Collide, PrimitiveCollisions, StaticArrays # Create two entities e = Collide.Entity( name = :a, shape = PrimitiveCollisions.Rect(1.0, 1.0), linear_drag = 0.5 ) e2 = Collide.Entity( name = :b, shape = PrimitiveCollisions.Rect(1.0, 1.0), position = SVector{2}(2.1, -1.2), velocity = SVector{2}(-1.0, 0.0), ) # Add them to the world world = Collide.World(:w) push!(world, e) push!(world, e2) sim = Collide.Simulation(w, [0., 0.]); # Add this semicolon or face pages of printed content # Step 10.0 seconds, stopping after exactly 10.0s Collide.step!(sim, 10.0, true)

• Entities that are intersecting when the collision starts will be stuck inside each other (they "collide from the inside").
• Entities that touch exactly (two circles at a distance equal to the sum of their radii) are also considered to intersect. To simulate things like Newton's cradle, separate the circles by a tiny distance (eps()).
• The internals are not yet documented, but not too complicated either.

A simple plotting function, and one to generate a bunch of random bodies inside a box, are available in this gist. Try the following:

sim, w = manybody(10, 10) animate(sim, w; tstep = 0.01, frames = 3000)