// BALL — the two-deck transition where the outgoing picture curls into a
// video ball and rolls away: at the A end the frame is exactly deck A; as
// the fader travels, a sphere wrapped in deck A inflates and rolls across
// while the backdrop dissolves to deck B underneath; at the B end the ball
// has shrunk to nothing and the frame is exactly deck B. ROLL spins the
// ball harder, ARC lifts its flight. Pattern taught here: the videomesh
// two-deck contract — `decks: 2` + `backdrop: 1`, every hook a function of
// the crossfader (self.user.w), scale zero at both ends keeping the
// endpoints pop-free.
{
    name: "Ball"
    engine: "videomesh"
    shape: "sphere"
    seed: 2

    detail: 40
    size: 2.4
    spread: 0.0
    decks: 2
    backdrop: 1
    fly: 0.05
    alt: 0.0

    beat_pulse: 0.2
    fog: 0.0
    glow: 1.0

    // Gallery/thumbnail preview sweep — in the VJ the host overrides p3
    // with the real crossfader.
    p3: "0.5 - 0.5*cos(6.28318*fract(beat/16.0))"

    dials: [
        {name: "ROLL", bind: "p0", default: 0.3},
        {name: "ARC", bind: "p1", default: 0.4}
    ]

    color_bg: #x000000
    color_a: #x40c8f0
    color_b: #xe84f9a
    color_c: #xffffff

    // THE LOOK LIVES HERE — the whole transition: backdrop deck mix,
    // ball flight, ball shading. t in fx_backdrop = the crossfader.
    shader: draw.DrawVjFxVideomesh {
        fx_axis: fn(id: float, hash: float) -> vec3 {
            return vec3(0.0, 0.0, 1.0)
        }
        fx_scale: fn(id: float, hash: float, t: float) -> float {
            let k = clamp(self.user.w, 0.0, 1.0)
            return 4.0 * k * (1.0 - k) * (1.0 + self.time_beat.w * 0.05)
        }
        fx_place: fn(id: float, hash: float, t: float) -> vec4 {
            let k = clamp(self.user.w, 0.0, 1.0)
            let x = (k * 2.0 - 1.0) * 3.4
            let y = sin(3.14159 * k) * (0.1 + 1.0 * clamp(self.user.y, 0.0, 2.0)) - 0.3
            let ang = 0.0 - k * (5.5 + 5.0 * clamp(self.user.x, 0.0, 2.0))
            return vec4(x, y, 0.0, ang)
        }
        fx_backdrop: fn(uv: vec2, t: float) -> vec4 {
            let m = smoothstep(0.22, 0.78, t)
            let a = self.deck_a(uv)
            let b = self.deck_b(uv)
            return vec4(a.xyz.mix(b.xyz, m), 1.0)
        }
        fx_color: fn(t: float, attr: vec4, content: vec4, cmix: float) -> vec4 {
            let sheen = self.col_c.xyz * pow(clamp(t - 0.9, 0.0, 1.0), 2.0) * 0.6
            return vec4(content.xyz * (0.35 + 0.75 * t) + sheen, 1.0)
        }
    }
}