Input and camera

Both belong to one player, so both are for ClientScripts. A server Script that touches input or camera gets an error saying so.

Keys

input.onKey("E", function()        -- pressed (not while the player types in the chat or a text box)
    net.send("interact")
end)

if input.isDown("LeftShift") then  -- held right now?
    print("sprinting")
end

Key names: "A" to "Z", "Zero" to "Nine", "Space", "Return", "Tab", "Backspace", "Escape", "LeftShift", "RightShift", "LeftControl", "RightControl", "LeftAlt", "RightAlt", "Up", "Down", "Left", "Right".

For everything - mouse buttons too, and key releases - use the raw events:

input.began:connect(function(inputObject, typing)
    if typing then return end            -- the player is typing in the chat or a box
    print(inputObject.type, inputObject.key)
end)

input.ended:connect(function(inputObject, typing)
    if inputObject.key == "LeftShift" then print("stopped sprinting") end
end)

Keys the game already uses

W A S D walk, Space jumps, Shift is camera lock, 1-0 pick tools, Tab the player list, Enter and / the chat, Esc the menu. Pick other keys for your game's own actions - E, F, Q, R...

On phones there is no keyboard: give every action a button on screen too (Scripting UI), or use a Prompt, which phones can tap.

What the mouse is over

game.frame:connect(function()
    local hit = world:raycast(camera:ray())   -- from the camera through the pointer
    if hit then
        marker.position = hit.position
    end
end)

camera:ray(distance?) returns an origin and a direction through the pointer - the mouse, the middle of the screen in camera lock or first person, or the last touch - 1,000 units long unless you say.

The camera

Until a script changes it, the camera is the game's own: it follows the character, the mouse turns it, the wheel zooms, and it keeps out of walls.

Member	What it is
camera.mode	"Follow" (the game's camera), "Fixed" (stays where a script puts it), "FirstPerson" (always the eyes)
camera.transform	Where it is and the way it looks. Setting it fixes the camera there
camera.position	Where it is; setting it fixes the camera
camera.fov	Field of view, 20 to 100 degrees (45 to start)
camera.target	What "Follow" orbits: a part, another player, or nil for your own character
camera.minZoom, camera.maxZoom	How near and far the wheel zooms, 0.5 to 400 units
camera.offset	Moves the point the camera turns about (x right, y up, z behind)
camera.firstPerson	True while the camera is the character's eyes (read-only)
camera.firstPersonArms	In first person, draw the player's own arms (true)
camera.viewportSize	The screen's size in UI points (read-only)
camera:toScreen(position)	Where a point in the world is on the screen, and whether it is in front
camera:tween(goals, time)	Smooth changes - a zoom, a cutscene

Examples

-- An overhead camera
camera.transform = transform.lookAt(vec3(0, 60, 40), vec3(0, 0, 0))
camera.fov = 50

-- Back to normal
camera.mode = "Follow"

-- A sprint that widens the view
input.began:connect(function(i, typing)
    if not typing and i.key == "LeftShift" then camera:tween({fov = 60}, 0.2) end
end)
input.ended:connect(function(i)
    if i.key == "LeftShift" then camera:tween({fov = 45}, 0.2) end
end)

-- A cutscene: fly between two parts, then give the camera back
camera:tween({transform = world.Shot1.transform}, 2).completed:wait()
camera:tween({transform = world.Shot2.transform}, 3).completed:wait()
camera.mode = "Follow"

-- Spectate another player
camera.target = someOtherPlayer

-- A marker over a part, in screen UI
local where, inFront = camera:toScreen(world.Goal.position)
marker.visible = inFront
marker.position = dim.px(where.x, where.y)

First person

Every world lets players zoom all the way in to first person, as Roblox does. To change how the camera starts for everyone, insert Camera settings (Insert > Camera settings) and set its Mode, Min zoom, Max zoom, Field of view, Arms in first person and Offset in the Inspector. A Min zoom of 2 or more keeps players out of first person.

A ClientScript changes its own player's camera from there:

-- A shooter: always first person, wide view, the pointer back for the shop
camera.mode = "FirstPerson"
camera.fov = 80

local shop = players.me.gui:waitFor("Shop")
input.onKey("B", function()
    shop.visible = not shop.visible
    input.mouseFree = shop.visible       -- show the pointer while the shop is open
end)

game.frame:connect(function()
    if camera.firstPerson then
        local hit = world:raycast(camera:ray(300))   -- what the crosshair is on
    end
end)

Camera lock

Players press Shift (or the padlock button on phones) for camera lock: the camera sits over the right shoulder, the pointer is hidden with a crosshair in the middle, and the body always faces where the camera looks. camera:ray() then goes through the crosshair. input.mouseFree = true frees the pointer here too.