Tutorials · Crypt Knight · Chapter 5

The knight

Name the controls

1. Choose View → Input map…. With no input map saved yet, the window starts on six actions of its own: left, right, up, down, jump and action. Select each of the six in turn and press Remove: your own replace them.
2. Type move into New action and press Add.
3. With move selected, press Add composite and choose WASD, then press Add composite again and choose Arrow keys. The list shows two Vector2 rows: W, S, A and D, and Up, Down, Left and Right.
4. Add an action called jump, press Record a control, and press Space.
5. Add an action called down, press Record a control, and press S. Press Record a control again, and press Down.
6. Press Save. The window writes input.ron into the project, and you can close it.

A body in the room

1. Select Gate, press + Add node, and choose Character. Rename it knight.
2. Set its Position to 72 and 160: a little way in from the left wall, standing on the start floor, whose top is at y 160. A body’s position is where its feet are.
3. In its CharacterBody, set Size to 12 and 30, and Driven By to Script. Leave Motion Mode on Grounded.
4. Set Gravity to 900, Terminal Velocity to 400 and Jump Speed to 295. Leave Speed at 220: a body driven by a script is never run at it.
5. In its Jumping fold, set Coyote Time to 0.1, Jump Buffer to 0.1 and Jump Cut to 0.5, and leave Air Jumps at 0.
6. In its Shape, keep Kind on Rectangle, set Size to 12 and 30, Anchor to 0.5 and 1, and Outline to 0, so the box stands on the node’s position with its feet.
7. Set the Shape’s Color to a crimson, 0.6, 0.01, 0.04, alpha 1, and its Sort Layer to 5, so it draws over the ground, which is at 0.

Driven By

Keys is the controller the engine ships: A and D or the arrows walk the body and Space jumps it. Script leaves all of that to the body’s own script, which sets its sideways speed and asks for its jumps. The knight is driven by its script, and so, later, are the enemies and the boss.

Size

The body’s box, 12 by 30 world units, and smaller than the 38 by 48 art it gets in chapter 7: the box is what walls and floors see, so a cape may brush a wall.

Gravity, Terminal Velocity and Jump Speed

How hard the world pulls the knight down, in units a second each second, how fast it may fall, and how fast a jump throws it up. Together they make a held jump rise about 48 units, three cells, in theory, and about 46 in the game, which steps in sixtieths of a second.

Coyote Time

Seconds after running off a ledge in which a jump still counts, as if from the ground. Without it, the jump that comes a hair late is the one the player blames.

Jump Buffer

Seconds a jump asked for just before landing waits to happen on landing: a press a moment early is still a jump.

Jump Cut

How much of the upward speed is kept when the jump is let go early. At 1 all of it, so Space only starts a jump; at 0.5, half, so a tap rises about a quarter as high as a held jump.

The knight’s script

1. In Assets, press Create, choose New script, type knight, and press Enter. The editor writes knight.rgs into the project folder.
2. Click the Code tab above the Viewport, then knight.rgs in its Scripts list, which shows every script in the project.
3. Replace everything in it with the script below, and press Ctrl+S. The panel says Up to date once the script checks.

/// The knight: runs where `move` points, jumps on `jump`, jumps lower when
/// `jump` is let go early, and drops through a ledge when `down` is held as it
/// jumps.
component Knight {
    /// How fast the knight runs.
    #[suffix("u/s")]
    speed: f32 = 110.0,

    fn loop() {
        set_number("CharacterBodyComponent", "velocity.x", direction("move").x * speed);
        let drop = pressed("jump") && held("down");
        set_flag("CharacterBodyComponent", "drop_through", drop);
        if pressed("jump") && !drop {
            jump();
        }
        if !held("jump") {
            cut_jump();
        }
    }
}

component Knight and speed

The script is a component called Knight, and its file is named after it, in lower case: knight.rgs. speed is a field: a row in the Inspector with this default, 110 units a second. The /// line above it is its tooltip.

fn loop()

A hook: it runs on every step of the game, 60 a second. Everything the knight does, it does here.

direction and set_number

direction("move") is where the action points, as a vector with each part from -1 to 1; .x is the sideways half, -1 for A, 1 for D and 0 for neither. set_number writes a number into a field of one of this node’s components, here the Character Body’s sideways velocity, velocity.x. A body driven by a script keeps whatever speed its script last gave it.

pressed and held

pressed("jump") is true on the step Space goes down, once. held("jump") is true on every step it stays down.

jump

Asks the body for a jump. The body honours its Coyote Time and its Jump Buffer, and its Air Jumps: asking in the air after running off a ledge, or just before landing, still jumps.

cut_jump

If the body is rising from a jump that has not been cut, keeps the Jump Cut’s share of its upward speed. The script calls it on every step Space is not held, so letting go in mid-rise cuts the jump short, and on the ground it does nothing.

set_flag and drop_through

The Character Body’s Drop Through says to ignore one-way ledges while leaving one. The script turns it on for the step on which Space goes down with S or Down held, and then does not jump: the knight falls through the ledge instead.

Give the knight its script

1. Click the Viewport tab, select knight, press Add component, and choose Knight. It is listed under a rule, below the built-in components, once its script checks: a script with a mistake in it is not offered.
2. Leave its Speed at 110, and press Ctrl+S.

Check it works