2. Break things¶

You'll throw balls, knock a tower of crates over and, with the everything build, shatter glass.

Throw a ball¶

Make a new file, scripts/throw.lua, in your game folder:

-- throw.lua: F throws a ball where the camera looks.
input.define("throw", "Throw a ball", "F")

hook.Add("Think", "throw.check", function()
  if input.pressed("throw") then
    local dir = camera.forward()
    physics.sphere {
      pos = camera.target() + dir * 0.6 + Vec(0, 0.6, 0),
      radius = 0.18,
      density = 3000,             -- heavy: it knocks things over
      velocity = dir * 18,        -- m/s
      color = Vec(0.9, 0.25, 0.2),
    }
  end
end)

Save, then press F. A few things to notice:

input.define makes a real action: it shows up in the controls settings, and players can rebind it.
hook.Add("Think", ...) runs your function every frame. The second argument is a name, so saving again replaces the hook instead of adding a second one.
camera.target() is the point the camera looks at, just above the character.

Build a tower to knock down¶

Add to throw.lua, and save:

-- A tower of wooden crates in front of the stairs.
for level = 0, 7 do
  for k = 0, 1 do
    local offset = (level % 2 == 0) and Vec(k * 0.62 - 0.31, 0, 0) or Vec(0, 0, k * 0.62 - 0.31)
    physics.box {
      pos = Vec(0, 0.31 + level * 0.62, -4) + offset,
      size = Vec(0.6, 0.6, 0.6),
      density = 120,
      color = Vec(0.62, 0.45, 0.28),
    }
  end
end

Everything a script makes belongs to it: when you save throw.lua again, the old tower and the balls you threw are removed before the new ones are made.

Shatter glass¶

With the everything preset the engine has AMD FEMFX, deformable bodies that really break, and the breakable table exists in Lua. Build it once (cmake --workflow --preset everything, it takes a while longer), then add:

-- Only in the "everything" build: a pane of glass and a stone block.
if breakable then
  breakable.box { pos = Vec(4, 0.61, 2), size = Vec(1.2, 1.2, 0.06), material = "glass" }
  breakable.box { pos = Vec(6, 0.4, 2), size = Vec(0.8, 0.8, 0.8), material = "stone" }
  hook.Add("Break", "throw.broke", function(id)
    print(string.format("Something broke: %d", id))
  end)
end

Materials are glass, stone, wood, ice and iron (which never breaks). The Break hook runs when a breakable your script made comes apart. The if breakable then keeps the same script working in the default build.

What you have¶

Your own action, a hook, and physics you can play with. Next: script a pickup.