// BEAT LENS — the optics preset: blobby GLASS floats in front of the
// camera and the channel's content (input0) is seen THROUGH it, bent by a
// real Snell refraction whose strength rides the pulse (p3). Pattern
// taught: a scene material < 0 marks glass — the base marcher refracts
// once and samples input0 along the bent ray; total internal reflection
// falls back to a mirror bounce (branched, never mix-guarded).
{
    name: "Beat Lens"
    engine: "raymarch"

    steps: 56
    max_dist: 20.0
    cam: "dolly"
    cam_speed: 0.5
    cam_dist: 5.2
    cam_height: 0.4
    cam_fov: 52.0
    shadow: 0

    beat_pulse: "0.8 * (0.2 + 1.6*p0)"
    beat_rate: 1.0
    fog: "0.03 * (0.2 + 1.6*p2)"
    glow: "0.25 + 1.5*p1"
    p3: "0.15 + 0.5 * pulse"   // IOR bend breathes on the beat (and the
                               // transition slot drives p3 with its engage
                               // triangle — the lens bends open mid-fade)

    // PERFORMANCE DIALS — mid-knob = the stock look, exact.
    p0: 0.5  p1: 0.5  p2: 0.5
    dials: [
        {name: "PUMP", bind: "p0", default: 0.5},
        {name: "GLOW", bind: "p1", default: 0.5},
        {name: "HAZE", bind: "p2", default: 0.5}
    ]

    input0: "test"

    color_bg: #x101018
    color_a: #x3060ff
    color_b: #x20d0ff
    color_c: #xffffff

    stages: [
        {kind: "bloom", threshold: 0.6, strength: 1.0, levels: 2}
    ]

    shader: draw.DrawVjFxRaymarch {
        scene_sdf: fn(p: vec3) -> vec2 {
            // Three lens-blobs breathing around the view axis.
            let t = self.time_beat.x
            let c1 = vec3(sin(t * 0.51) * 1.7, sin(t * 0.73) * 1.0, sin(t * 0.37) * 0.7)
            let c2 = vec3(cos(t * 0.61 + 2.0) * 1.4, cos(t * 0.43 + 1.0) * 1.2, cos(t * 0.53) * 0.6)
            let c3 = vec3(sin(t * 0.29 + 4.2) * 1.1, cos(t * 0.67 + 3.1) * 0.8, sin(t * 0.47 + 1.7) * 0.8)
            let mut d = length(p - c1) - 1.15
            d = self.smin(d, length(p - c2) - 0.95, 0.7)
            d = self.smin(d, length(p - c3) - 0.80, 0.7)
            // material -1 = GLASS: refract and sample input0.
            return vec2(d, 0.0 - 1.0)
        }
    }
}