Recursive AI
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Quick start

OnePhysics 0.4.0-preview.1docs/guide/quick-start.md at fa8eed5 Markdown

All onephysics docs

The namespaces you import: RecursiveAI.OneMath for the vector types, RecursiveAI.OnePhysics for what both dimensions share (BodyType, EventKind, EventMask, exceptions, raw handles), and RecursiveAI.OnePhysics.Physics2D (or Physics3D) for the world, Body, Shape, Joint, Character and the definitions.

A world, some bodies, a step loop

C#
var world = new PhysicsWorld2D();
var ground = world.AddBox(new Vector2F(20, 1), at: new Vector2D(0, -0.5), type: BodyType.Static);
var crate = world.AddBox(new Vector2F(1, 1), at: new Vector2D(0, 3), material: new Material2D(friction: 0.8f));
var ball = world.AddCircle(0.5f, at: new Vector2D(2, 4));
ball.LinearVelocity = new Vector2F(-1, 0);
crate.OnCollisionEnter += c => Console.WriteLine($"crate hit {c.Other}");
for (int i = 0; i < 120; i++) world.Step(1f / 60);
Console.WriteLine($"{crate.Position} {crate.LinearVelocity} awake={crate.IsAwake}");
  • Positions are double (Vector2D); sizes, velocities and everything else are float (Vector2F).
  • AddBox(size) takes the full size. See units.
  • Body is a small struct. Copy it freely; it allocates nothing. After body.Destroy() any use throws StaleHandleException.
  • Step takes a fixed dt. The world has no clock; always pass the same value (see determinism). After the step, handlers run and the events of the step are available to poll (events).

A character and a ray

C#
var player = world.AddCharacter(at: new Vector2D(-3, 1));
player.Move(new Vector2F(0.05f, -0.1f), 1f / 60);   // this frame's displacement, not a velocity
world.Step(1f / 60);
bool grounded = player.IsGrounded;
if (world.Raycast(new Vector2D(0, 10), new Vector2F(0, -1), out var hit)) Console.WriteLine($"{hit.Body} at {hit.Point}, {hit.Distance} away");

Move takes the displacement for this frame (use MoveVelocity for a velocity times dt) and slides along slopes, climbs steps and pushes bodies; CharacterDef.Humanoid, Child and Giant are presets, and AddCharacter(at, def) takes your own tuned copy.

3D, a preview

The 3D engine is [Experimental("OPHYS0002")]; acknowledge it with #pragma warning disable OPHYS0002 or a NoWarn. The world has the same members with 3D math types.

C#
var world = new PhysicsWorld3D();
world.AddBox(new Vector3F(20, 1, 20), at: new Vector3D(0, -0.5, 0), type: BodyType.Static);
var crate = world.AddBox(new Vector3F(1, 1, 1), at: new Vector3D(0, 3, 0));
var ball = world.AddSphere(0.5f, at: new Vector3D(2, 4, 0));
for (int i = 0; i < 120; i++) world.Step(1f / 60);
Console.WriteLine($"{crate.Position} {ball.Position}");

To use both dimensions in one file, import neither dimension namespace and alias what you use: using Body2D = RecursiveAI.OnePhysics.Physics2D.Body; and using Body3D = RecursiveAI.OnePhysics.Physics3D.Body;.

Next

The three tiers for definitions, filters and polled events; rollback if your host resimulates.