Tutorials · Crypt Knight · Chapter 12

The sword

A slash that hurts only when it swings

An attack action

1. Choose View → Input map…. Type attack into New action and press Add.
2. With attack selected, press Record a control and press J. Press Record a control again and press X.
3. Press Save, and close the window.

Pack the sheet again

1. Copy the two pictures above into art, and press Refresh in Assets.
2. In Assets, open art, right-click hero.png and choose Delete. The window lists the scenes that still use it: confirm. Do the same for hero.anim.
3. Right-click gothic-hero-attack.png and choose Make Animation…. It opens with that picture ticked. Tick gothic-hero-hurt.png, gothic-hero-idle.png, gothic-hero-jump.png and gothic-hero-run.png too: five in all, played in name order.
4. Set Name to hero, leave Frames a second and Loop as they are, and press Create. It writes art/hero.png, a sheet of the five strips side by side, again 2048 by 128, and art/hero.anim, one clip called hero that plays them.

1. Select knight, so that the Animation panel shows hero.anim, and double-click art/hero.png in Assets: the Sprite sheet tab opens on it.
2. Idle. Set Cell to 38 and 48, Margin to 1679 and 0. Drag across the first four cells of the top row: Selected 4 x 1. Press From selection; name it idle, 8 fps, Loop; press Generate 1 and Clear.
3. Run. Cell 66 and 48, Margin 307 and 0. Drag from cell 0, 0 to 11, 0: Selected 12 x 1. From selection; run, 14 fps, Loop; Generate 1 and Clear.
4. Jump. Cell 61 and 77, Margin 0 and 0. Drag from cell 0, 0 to 2, 0: Selected 3 x 1. From selection; jump, 12 fps, Once; Generate 1 and Clear.
5. Fall. Keep that grid. Drag from 3, 0 to 4, 0: Selected 2 x 1. From selection; fall, 8 fps, Once; Generate 1 and Clear.
6. Hurt. Cell 48 and 48, Margin 1833 and 0. Drag from 0, 0 to 2, 0: Selected 3 x 1. From selection; hurt, 10 fps, Once; Generate 1 and Clear.
7. Slash. Cell 96 and 48, Margin 1101 and 0. Drag from 0, 0 to 5, 0: Selected 6 x 1. From selection; slash, 18 fps, Once; Generate 1 and Clear.
8. In the Animation panel, press Save. The panel lists hero (5), idle (4), run (12), jump (3), fall (2), hurt (3) and slash (6).

1. In the Animation panel, click jump. Under Frames, double-click the y box of the pivot, type 0.987, and press Enter. Press Next frame, and set y to 0.870; again, 0.623. Click fall: 0.545, Next frame, 0.779.
2. Click hurt. Double-click the pivot x box, type 0.61, press Enter, press Next frame, and do it again, for all three frames.
3. Click slash. Set pivot x to 0.47, Next frame, and so on, for all six.
4. Press Save, and Ctrl+S.

1. With slash chosen, under the frame strip type slash into Track name, choose Active, and press Add track. A row called slash appears in the grid above, with a cell for each of the clip’s six frames.
2. Drag across the third and fourth cells, frames 2 and 3, counting from 0, in the slash row: they fill with orange. Frames 2 and 3 are the swoosh and the full reach of the swing.
3. Press Save, and Ctrl+S.

Active track

A track is a row of the clip’s frames, set on some. An Active one is a state held across its frames: while the clip is on a set frame, the track is on. A Trigger one fires once as its frame begins. Chapter 14 will use a Trigger for a sound.

The sword’s reach

1. In Assets, press Create, choose New script, type blade, and press Enter.
2. In the Code tab’s Scripts list, click blade.rgs, replace everything in it with the script below, and press Ctrl+S.

/// The knight's sword's reach: an Area on a node of its own under the knight,
/// which the slash clip's `slash` track shows on the swing's two frames. It
/// reaches out on the side the knight faces, which the knight keeps as
/// `facing`.
component Blade {
    /// How far from the knight the middle of the reach is.
    #[suffix("u")]
    reach: f32 = 22.0,

    fn loop() {
        set_point("AreaComponent", "shape.offset", vec2(kept_number("facing", 1.0) * reach, -16.0));
    }
}

1. Click the Viewport tab. Select knight, press + Add node, and choose Area: it lands under knight. Rename it slash and untick its Visible: the clip shows it, below. Under Groups, type slash.
2. In its Area, set the Shape’s Size to 32 and 24, and its Offset to 22 and -16: a box in front of the knight, at the height of his sword arm.
3. Set the Area’s own Layer to 2, untick 0 in its Mask so it reads Nothing, and set its Track to slash.
4. Press Add component and choose Blade. Leave its Reach at 22.
5. With slash selected, press Ctrl+C, then Ctrl+S. Open scenes/crypt.ron, right-click knight, choose Paste as child, and press Ctrl+S: the Crypt’s knight carries the same reach.

The knight swings

/// The knight: runs where `move` points, jumps on `jump`, jumps lower when
/// `jump` is let go early, drops through a ledge when `down` is held as it
/// jumps, jumps once more in the air once the relic is taken, faces the way it
/// last moved, and shows the clip for what it is doing. Once the sword is
/// taken, `attack` slashes, and a slash that lands pushes the knight back a
/// little. It keeps where it last stood on safe ground. A spike or a pit costs
/// it a heart and puts it back there; an enemy costs it a heart and hops it
/// back. A hurt shakes the camera, blinks the knight and plays its hurt clip,
/// and nothing can hurt it while it blinks. A heart it picks up heals one.
/// With no hearts left, the level is lost.

    /// Seconds of the hop, or of a slash's push back, still to run.
    #[hidden]
    hopping: f32 = 0.0,
    /// Seconds from one slash to the next.
    #[suffix("s")]
    cooldown: f32 = 0.4,
    /// How long the slash clip plays: six frames at 18 a second.
    #[suffix("s")]
    slash_time: f32 = 0.33,
    /// How long the hurt clip plays: three frames at 10 a second.
    #[suffix("s")]
    hurt_time: f32 = 0.3,
    /// How fast a slash that lands pushes the knight back.
    #[suffix("u/s")]
    recoil_speed: f32 = 80.0,
    /// How long that push lasts.
    #[suffix("s")]
    recoil_time: f32 = 0.1,
    /// Seconds until the knight may slash again.
    #[hidden]
    readying: f32 = 0.0,
    /// Seconds of the slash clip still to play.
    #[hidden]
    slashing: f32 = 0.0,
    /// Seconds of the hurt clip still to play.
    #[hidden]
    hurting: f32 = 0.0,

        // A slash that landed: what it struck says "recoil" to the group
        // "knight", heard a step later. The push goes the opposite way to the
        // way the knight faces, and steering waits for it to end.
        if heard("recoil") {
            set_number("CharacterBodyComponent", "velocity.x", -facing * recoil_speed);
            hopping = recoil_time;
        }

            // Hopping back from a hurt, or pushed back by a slash: the push
            // keeps its own speed.

        // The sword's reach reads which way the knight faces.
        keep_number("facing", facing);
        // The slash: once the sword is taken, attack starts one, when the last
        // has cooled and no hurt is playing.
        if readying > 0.0 {
            readying -= dt;
        }
        if pressed("attack") && kept_number("sword", 0.0) > 0.0 && readying <= 0.0 && hurting <= 0.0 {
            play_clip("slash");
            shown = "slash";
            slashing = slash_time;
            readying = cooldown;
        }

        // A slash, and over anything a hurt, plays to its end.
        if slashing > 0.0 {
            slashing -= dt;
            want = "slash";
        }
        if hurting > 0.0 {
            hurting -= dt;
            want = "hurt";
        }

                // The hurt clip plays over whatever the knight was doing.
                hurting = hurt_time;

play_clip "slash" and shown

Starts the slash from its first frame. Setting shown to "slash" tells the code below that the clip on show is already the slash, so it does not start it again. slashing is how long it plays, 0.33 seconds, and the swing is the same length wherever he is: running, standing, in the air.

pressed("attack") and kept_number("sword", 0.0)

A press of J or X, and the sword: the relic of chapter 11 keeps a 1 under sword, and until it does, a press does nothing. readying is the cooldown, 0.4 seconds, and hurting is whether the hurt clip is playing: a hurt knight cannot swing.

keep_number("facing", facing)

The reach, a different node, cannot read the knight’s facing, a field of his script. So the knight keeps it, as a kept value, every step, and Blade reads it back.

heard("recoil")

What a slash strikes says "recoil" to the group knight, as a heart says "heal", and the knight hears it a step later, and is pushed back at recoil_speed for recoil_time: 80 units a second for a tenth of a second, which is 8 units.

Creatures that are struck

1. In Assets, press Create, choose New script, type struck, and press Enter.
2. In the Code tab’s Scripts list, click struck.rgs, replace everything in it with the script below, and press Ctrl+S.

/// A creature the knight's sword can strike: a slash that lands on it pushes
/// the knight back.
component Struck : Area {
    fn on_enter(other: NodeId) {
        if in_group(other, "slash") {
            // The knight is in the group "knight", and is pushed back a step
            // later.
            emit_to("knight", "recoil");
        }
    }
}

1. Click the Viewport tab, and in scenes/crypt.ron select hound_1.
2. In its Area, click the Mask row, and tick 2, so that it reads 2: it now looks for the reach.
3. Press Add component and choose Struck.
4. Do the same for hound_2, skull and wolf, and press Ctrl+S.

Check it works