feat(physics): a walker (Jolt CharacterVirtual with an inner body) and the verbs a boat and a guest's copy need - force, torque, angular impulse, spin, set_pose

Five new tests: stand and walk at the asked speed, a low stone is a step and a tall one a wall, a
jump up and back, a crate shoved aside, a hull turned by a torque and carried by a force.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.physics/tests/walker_test.ludic

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+# walker_test.ludic - a walker on the real Jolt: it stands, walks, steps onto a low stone, is held
+# by a tall one, jumps and lands, shoves a crate aside; and a boat-shaped body turns under a torque
+import "ludic.physics"
+import "ludic.base"
+program WalkerTest {
+  numbers float
+
+  function flat(physics_st: mut PhysicsState) -> void {
+    expect(phys_open(physics_st, 1024, 1))
+    let h = floats(64 * 64)
+    for i in 0 .. 64 * 64 { h[i] = 0.0 }
+    phys_ground_add(physics_st, phys_heightfield(physics_st, h, 64, -32.0, -32.0, 1.0))
+  }
+
+  function walk(physics_st: mut PhysicsState, id: int, seconds: float, vx: float, vz: float) -> void {
+    for i in 0 .. int(seconds * 60.0) { phys_walker_step(physics_st, id, 1.0 / 60.0, vx, vz, 0.0) }
+  }
+
+  test "a walker falls to the ground, stands, and walks at the speed it asks" (physics_st: mut PhysicsState) {
+    flat(physics_st)
+    let me = phys_walker_add(physics_st, 0.35, 1.8, 0.0, 1.0, 0.0, 50.0, 70.0)
+    walk(physics_st, me, 1.0, 0.0, 0.0)
+    let p = phys_walker_pose(physics_st, me)
+    expect_eq(p.ground, PHYS_ON_GROUND)
+    expect(Math.abs(p.y) < 0.05)
+    walk(physics_st, me, 2.0, 3.0, 0.0)
+    let q = phys_walker_pose(physics_st, me)
+    expect(Math.abs(q.x - 6.0) < 0.2)
+    expect(q.body >= 0)
+    phys_close(physics_st)
+  }
+
+  test "a low stone is a step, a tall one is a wall" (physics_st: mut PhysicsState) {
+    flat(physics_st)
+    let stone = phys_offset(physics_st, phys_box(physics_st, 1.0, 0.15, 3.0), 0.0, 0.15, 0.0, 0.0)
+    phys_static_add(physics_st, stone, 3.0, 0.0, 0.0, 0.0)
+    let wall = phys_offset(physics_st, phys_box(physics_st, 1.0, 1.5, 3.0), 0.0, 1.5, 0.0, 0.0)
+    phys_static_add(physics_st, wall, 3.0, 0.0, 10.0, 0.0)
+    phys_settle(physics_st)
+    let a = phys_walker_add(physics_st, 0.35, 1.8, 0.0, 0.0, 0.0, 50.0, 70.0)
+    phys_walker_limits(physics_st, a, 0.55, 0.5)
+    walk(physics_st, a, 1.5, 2.0, 0.0)
+    let pa = phys_walker_pose(physics_st, a)
+    expect(pa.x > 2.5)
+    expect(Math.abs(pa.y - 0.3) < 0.05)
+    let b = phys_walker_add(physics_st, 0.35, 1.8, 0.0, 0.0, 10.0, 50.0, 70.0)
+    walk(physics_st, b, 2.0, 2.0, 0.0)
+    let pb = phys_walker_pose(physics_st, b)
+    expect(pb.x < 1.7)
+    expect(Math.abs(pb.y) < 0.05)
+    phys_close(physics_st)
+  }
+
+  test "a jump leaves the ground and comes back down" (physics_st: mut PhysicsState) {
+    flat(physics_st)
+    let me = phys_walker_add(physics_st, 0.35, 1.8, 0.0, 0.0, 0.0, 50.0, 70.0)
+    walk(physics_st, me, 0.5, 0.0, 0.0)
+    phys_walker_step(physics_st, me, 1.0 / 60.0, 0.0, 0.0, 5.0)
+    walk(physics_st, me, 0.25, 0.0, 0.0)
+    let up = phys_walker_pose(physics_st, me)
+    expect_eq(up.ground, PHYS_IN_AIR)
+    expect(up.y > 0.5)
+    walk(physics_st, me, 1.5, 0.0, 0.0)
+    let down = phys_walker_pose(physics_st, me)
+    expect_eq(down.ground, PHYS_ON_GROUND)
+    expect(Math.abs(down.y) < 0.05)
+    phys_close(physics_st)
+  }
+
+  test "walking into a crate shoves it, and a placed walker stands where it was put" (physics_st: mut PhysicsState) {
+    flat(physics_st)
+    let crate = phys_body_add(physics_st, phys_box(physics_st, 0.25, 0.25, 0.25), 2.0, 0.25, 0.0, 0.0, 4.0)
+    let me = phys_walker_add(physics_st, 0.35, 1.8, 0.0, 0.0, 0.0, 50.0, 70.0)
+    for i in 0 .. 150 {
+      phys_walker_step(physics_st, me, 1.0 / 60.0, 2.0, 0.0, 0.0)
+      phys_step(physics_st)
+    }
+    expect(phys_pose(physics_st, crate).x > 2.5)
+    phys_walker_place(physics_st, me, -10.0, 0.0, -10.0)
+    let p = phys_walker_pose(physics_st, me)
+    expect(Math.abs(p.x + 10.0) < 0.01)
+    phys_walker_remove(physics_st, me)
+    expect(phys_walker_pose(physics_st, me) == null)
+    phys_close(physics_st)
+  }
+
+  test "a torque turns a body and a force carries it" (physics_st: mut PhysicsState) {
+    expect(phys_open(physics_st, 64, 1))
+    phys_gravity(physics_st, 0.0)
+    let hull = phys_body_add(physics_st, phys_box(physics_st, 0.6, 0.2, 1.8), 0.0, 0.0, 0.0, 0.0, 120.0)
+    for i in 0 .. 60 {
+      phys_torque(physics_st, hull, 0.0, 200.0, 0.0)
+      phys_force(physics_st, hull, 0.0, 0.0, 240.0)
+      phys_step(physics_st)
+    }
+    expect(phys_spin_y(physics_st, hull) > 0.1)
+    expect(phys_pose(physics_st, hull).z > 0.5)
+    let p = phys_pose(physics_st, hull)
+    p.x = 5.0
+    phys_set_pose(physics_st, hull, p)
+    expect(Math.abs(phys_pose(physics_st, hull).x - 5.0) < 0.01)
+    phys_close(physics_st)
+  }
+}