example.osl

/*
 * fluid_noise.osl  —  Fluid-like noise shader for Blender Cycles
 *
 * Presets (dropdown in node UI):
 *   jupiter     — toxic lime/orange alien storm
 *   deep_ocean  — slow deep-sea thermals
 *   magma       — lava flow / pyroclastic
 *   aurora      — polar light curtains
 *   inkdrop     — ink diffusing in water, near-monochrome
 *   custom      — use all manual inputs as-is
 */

#include "stdosl.h"


/* ═══════════════════════════════════════════════════════════════════════
   Utilities
   ═══════════════════════════════════════════════════════════════════════ */

float fbm(point p, int octaves, float persistence, float lacunarity)
{
    float val  = 0.0, amp = 0.5, freq = 1.0, norm = 0.0;
    for (int i = 0; i < octaves; i++) {
        val  += amp * (float)noise("perlin", p * freq);
        norm += amp;
        amp  *= persistence;
        freq *= lacunarity;
    }
    return val / max(norm, 1e-5);
}

float pot(point p, float seed)
{
    return (float)noise("perlin",
        p + vector(seed*1.71934, seed*0.31271, seed*2.18413));
}

vector curlNoise(point p, float eps)
{
    float ie = 0.5 / eps;
    vector ex = vector(eps,0,0), ey = vector(0,eps,0), ez = vector(0,0,eps);
    float cx = (pot(p+ey,2.0)-pot(p-ey,2.0)-pot(p+ez,1.0)+pot(p-ez,1.0))*ie;
    float cy = (pot(p+ez,0.0)-pot(p-ez,0.0)-pot(p+ex,2.0)+pot(p-ex,2.0))*ie;
    float cz = (pot(p+ex,1.0)-pot(p-ex,1.0)-pot(p+ey,0.0)+pot(p-ey,0.0))*ie;
    return vector(cx, cy, cz);
}

color ramp(float t,
           float s0, color c0, float s1, color c1,
           float s2, color c2, float s3, color c3,
           float s4, color c4)
{
    float tt = clamp(t, 0.0, 1.0);
    if (tt <= s0) return c0;
    if (tt >= s4) return c4;
    if (tt < s1)  return mix(c0, c1, (tt-s0)/max(s1-s0,1e-5));
    if (tt < s2)  return mix(c1, c2, (tt-s1)/max(s2-s1,1e-5));
    if (tt < s3)  return mix(c2, c3, (tt-s2)/max(s3-s2,1e-5));
                  return mix(c3, c4, (tt-s3)/max(s4-s3,1e-5));
}


/* ═══════════════════════════════════════════════════════════════════════
   Main shader
   ═══════════════════════════════════════════════════════════════════════ */

shader fluid_noise(

    /* ── Spatial / time ─────────────────────────────────── */
    point  Pos            = P,
    float  Scale          = 2.5,
    float  Time           = 0.0,

    /* ── Preset selector — renders as a dropdown in Blender ─ */
    string Preset         = "jupiter"
        [[ string widget  = "popup",
           string options = "jupiter|deep_ocean|magma|aurora|inkdrop|custom" ]],

    /* ── Manual overrides (only matter when Preset = "custom") ─ */
    int    Octaves        = 8,
    float  Persistence    = 0.52,
    float  Lacunarity     = 2.3,
    float  WarpStrength   = 1.4,
    int    WarpIterations = 4,
    float  CurlEps        = 0.004,
    float  VorticityBlend = 0.55,
    float  Contrast       = 1.6,
    float  Brightness     = 0.0,
    float  TimeDrift      = 0.07,

    /* ── Custom colour stops ────────────────────────────── */
    color  Col0           = color(0.00, 0.00, 0.00),
    color  Col1           = color(0.05, 0.18, 0.02),
    color  Col2           = color(0.30, 0.72, 0.00),
    color  Col3           = color(0.82, 0.88, 0.00),
    color  Col4           = color(0.92, 0.38, 0.00),

    output float Fac      = 0.0,
    output color Color    = 0.0
)
{
    /* ═══════════════════════════════════════════════════════════════════
       Stage 0 — load preset values
       Each preset writes into these working variables, which are then
       used for ALL subsequent computation, not just colour.
       ═══════════════════════════════════════════════════════════════════ */

    int   p_octaves   = Octaves;
    float p_persist   = Persistence;
    float p_lacun     = Lacunarity;
    float p_warpStr   = WarpStrength;
    int   p_warpIter  = WarpIterations;
    float p_curlEps   = CurlEps;
    float p_vortBlend = VorticityBlend;
    float p_contrast  = Contrast;
    float p_bright    = Brightness;
    float p_drift     = TimeDrift;
    float p_scale     = Scale;

    /* colour stops */
    float ps0 = 0.00; color pc0 = Col0;
    float ps1 = 0.25; color pc1 = Col1;
    float ps2 = 0.50; color pc2 = Col2;
    float ps3 = 0.75; color pc3 = Col3;
    float ps4 = 1.00; color pc4 = Col4;

    /* ── Jupiter ─────────────────────────────────────────────────────────
     * Tight high-frequency swirls, strong vortex filaments, fast motion.
     * Bulk of the field sits in the lime band; orange only at peaks.     */
    if (Preset == "jupiter") {
        p_octaves   = 8;
        p_persist   = 0.52;
        p_lacun     = 2.30;
        p_warpStr   = 1.40;
        p_warpIter  = 4;
        p_curlEps   = 0.004;
        p_vortBlend = 0.55;
        p_contrast  = 1.60;
        p_bright    = 0.00;
        p_drift     = 0.07;
        p_scale     = 2.50;

        ps0 = 0.00; pc0 = color(0.01, 0.02, 0.00);
        ps1 = 0.22; pc1 = color(0.04, 0.18, 0.01);
        ps2 = 0.48; pc2 = color(0.45, 0.82, 0.00);
        ps3 = 0.70; pc3 = color(0.78, 0.76, 0.00);
        ps4 = 1.00; pc4 = color(0.90, 0.34, 0.00);
    }

    /* ── Deep ocean ──────────────────────────────────────────────────────
     * Very slow large-scale rolls, low lacunarity (broad swirls), gentle
     * vorticity. Feels like thermohaline convection.                     */
    else if (Preset == "deep_ocean") {
        p_octaves   = 6;
        p_persist   = 0.58;     /* smoother, rounder shapes              */
        p_lacun     = 1.80;     /* lower = larger, fewer curls           */
        p_warpStr   = 0.90;
        p_warpIter  = 3;
        p_curlEps   = 0.006;
        p_vortBlend = 0.20;     /* soft, not filament-y                  */
        p_contrast  = 1.20;
        p_bright    = 0.05;
        p_drift     = 0.025;    /* very slow evolution                   */
        p_scale     = 1.80;

        ps0 = 0.00; pc0 = color(0.00, 0.00, 0.05);
        ps1 = 0.20; pc1 = color(0.00, 0.06, 0.24);
        ps2 = 0.45; pc2 = color(0.00, 0.28, 0.55);
        ps3 = 0.68; pc3 = color(0.00, 0.62, 0.72);
        ps4 = 1.00; pc4 = color(0.40, 0.95, 0.95);
    }

    /* ── Magma ───────────────────────────────────────────────────────────
     * Sluggish top-level warp but lots of fine detail octaves. Strong
     * contrast to keep most of the field dark with bright crack-like
     * filaments.  Slow drift speed.                                      */
    else if (Preset == "magma") {
        p_octaves   = 9;        /* lots of fine crust-crack detail       */
        p_persist   = 0.48;
        p_lacun     = 2.50;     /* very fine veining                     */
        p_warpStr   = 1.80;     /* heavy warp to break up any regularity */
        p_warpIter  = 4;
        p_curlEps   = 0.003;
        p_vortBlend = 0.70;     /* strong filaments = glowing crack edges*/
        p_contrast  = 2.20;     /* most field is dark; peaks burn bright */
        p_bright    = -0.08;    /* pull midtones down toward black       */
        p_drift     = 0.018;    /* lava is slow                          */
        p_scale     = 3.00;

        ps0 = 0.00; pc0 = color(0.00, 0.00, 0.00);
        ps1 = 0.28; pc1 = color(0.22, 0.00, 0.00);
        ps2 = 0.55; pc2 = color(0.72, 0.06, 0.00);
        ps3 = 0.78; pc3 = color(0.98, 0.50, 0.00);
        ps4 = 1.00; pc4 = color(1.00, 0.96, 0.82);
    }

    /* ── Aurora ──────────────────────────────────────────────────────────
     * Tall vertical curtains — low warp iterations, higher persistence
     * for dreamy soft bands. Very low drift (aurora moves slowly).       */
    else if (Preset == "aurora") {
        p_octaves   = 5;
        p_persist   = 0.65;     /* soft, washy forms                     */
        p_lacun     = 1.90;
        p_warpStr   = 0.70;     /* gentle — keeps the curtain structure  */
        p_warpIter  = 2;        /* fewer warp passes = less tangled      */
        p_curlEps   = 0.007;
        p_vortBlend = 0.30;
        p_contrast  = 1.10;
        p_bright    = 0.08;
        p_drift     = 0.012;
        p_scale     = 1.50;

        ps0 = 0.00; pc0 = color(0.01, 0.00, 0.08);
        ps1 = 0.22; pc1 = color(0.08, 0.00, 0.32);
        ps2 = 0.48; pc2 = color(0.00, 0.52, 0.62);
        ps3 = 0.72; pc3 = color(0.22, 0.90, 0.72);
        ps4 = 1.00; pc4 = color(0.88, 0.96, 1.00);
    }

    /* ── Inkdrop ─────────────────────────────────────────────────────────
     * Ink diffusing in water. Maximum domain warp iterations and high
     * vorticity for micro-tendrils. Near-monochrome: deep indigo → cream.
     * Medium speed.                                                      */
    else if (Preset == "inkdrop") {
        p_octaves   = 8;
        p_persist   = 0.55;
        p_lacun     = 2.20;
        p_warpStr   = 2.20;     /* very tangled — ink doesn't flow clean */
        p_warpIter  = 5;        /* maximum nesting                       */
        p_curlEps   = 0.003;
        p_vortBlend = 0.80;     /* the tendrils ARE the point            */
        p_contrast  = 1.80;
        p_bright    = -0.05;
        p_drift     = 0.055;
        p_scale     = 2.80;

        ps0 = 0.00; pc0 = color(0.02, 0.01, 0.06);
        ps1 = 0.25; pc1 = color(0.10, 0.06, 0.28);
        ps2 = 0.50; pc2 = color(0.28, 0.22, 0.50);
        ps3 = 0.74; pc3 = color(0.70, 0.68, 0.78);
        ps4 = 1.00; pc4 = color(0.96, 0.94, 0.92);
    }

    /* "custom" — all p_ variables already hold the manual input values  */


    /* ═══════════════════════════════════════════════════════════════════
       Stage 1 — base position
       ═══════════════════════════════════════════════════════════════════ */
    point base = Pos * p_scale + vector(0.0, 0.0, Time * p_drift);


    /* ═══════════════════════════════════════════════════════════════════
       Stage 2 — iterative curl domain warp
       ═══════════════════════════════════════════════════════════════════ */
    point warped = base;
    float wAmp   = p_warpStr;
    for (int i = 0; i < p_warpIter; i++) {
        float s  = pow(1.75, (float)i);
        vector c = curlNoise(warped * s, p_curlEps) / s;
        warped   = warped + c * wAmp;
        wAmp    *= 0.52;
    }


    /* ═══════════════════════════════════════════════════════════════════
       Stage 3 — FBM at warped position
       ═══════════════════════════════════════════════════════════════════ */
    float f = fbm(warped, p_octaves, p_persist, p_lacun);


    /* ═══════════════════════════════════════════════════════════════════
       Stage 4 — vorticity confinement overlay
       ═══════════════════════════════════════════════════════════════════ */
    vector cv  = curlNoise(warped * p_lacun, p_curlEps * 0.45);
    float  vrt = smoothstep(0.0, 1.6, length(cv));
    f = mix(f, f + vrt * 0.30, p_vortBlend);


    /* ═══════════════════════════════════════════════════════════════════
       Stage 5 — large-eddy drift
       ═══════════════════════════════════════════════════════════════════ */
    float driftX = (float)noise("perlin", base*0.22 + vector(Time*0.035, 0.0,       0.0));
    float driftY = (float)noise("perlin", base*0.22 + vector(0.0,       Time*0.028, 0.0));
    point drifted = warped + vector(driftX, driftY, 0.0) * 0.16;
    f += (float)noise("perlin", drifted * 0.45) * 0.10;


    /* ═══════════════════════════════════════════════════════════════════
       Stage 6 — remap, contrast, output
       ═══════════════════════════════════════════════════════════════════ */
    float raw = clamp(f * 0.5 + 0.5, 0.0, 1.0);
    Fac = clamp((raw - 0.5) * p_contrast + 0.5 + p_bright, 0.0, 1.0);

    Color = ramp(Fac, ps0,pc0, ps1,pc1, ps2,pc2, ps3,pc3, ps4,pc4);
}