// Starfield Generator
// HMS MediaEngine – Generator (kein Eingangstextur-Bezug, cbuffer identisch §14.4)
// D3D11-Pixelshader (PS_5_0). Semantik identisch zu GL/GLES (§12.6, §15.1).

Texture2D    u_input_texture : register(t0);
SamplerState u_sampler       : register(s0);

cbuffer hms_params : register(b0)
{
    float4 u_resolution;     // xy = Auflösung in Pixeln
    float  u_time_seconds;
    float  u_delta_seconds;
    float  u_frame_index;
    float  u_layer_opacity;
    float  u_audio_rms;
    float  u_audio_peak;
    float  u_audio_bass;
    float  u_audio_mid;
    float  u_audio_treble;
    float  u_audio_beat;
    float4 param_color_a;
    float4 param_color_b;
    float param_count;
    float param_size;
    float param_speed;
    float param_direction_x;
    float param_direction_y;
    float param_depth;
    float param_twinkle;
    float param_seed;
    float  u_quality_samples; // AQ-Variante (Backend-Bindung)
    float  _pad0;             // 16-Byte-Alignment
};

float hash21(float2 p)
{
    p = frac(p * float2(123.34, 456.21));
    p += dot(p, p + 45.32);
    return frac(p.x * p.y);
}

float4 mainPS(float4 pos : SV_POSITION, float2 uv : TEXCOORD0) : SV_Target
{
    float2 p = uv;
    float t = u_time_seconds * param_speed;
    float maxN = clamp(u_quality_samples, 1.0, 512.0);
    float dl = length(float2(param_direction_x, param_direction_y));
    float2 dir = dl > 1e-4 ? float2(param_direction_x, param_direction_y) / dl : float2(0.0, -1.0);
    float acc = 0.0;
    float colAcc = 0.0;
    [loop]
    for (int i = 0; i < 512; i++)
    {
        if (float(i) >= maxN) { break; }
        float2 base = float2(hash21(float2(float(i) + param_seed, 1.0)), hash21(float2(float(i) + param_seed, 2.0)));
        float depth = hash21(float2(float(i) + param_seed, 3.0)) * param_depth;
        float2 pos = base + dir * t * (0.1 + depth * 0.9);
        pos = frac(pos);
        float2 d = pos - p;
        d = abs(d);
        d = min(d, 1.0 - d);
        float dist = length(d);
        float s = param_size * (0.3 + depth);
        float star = exp(-dist * dist / max(s * s, 1e-5));
        float tw = 0.5 + 0.5 * sin(t * 3.0 + param_seed * 10.0 + float(i) * 1.7);
        star *= lerp(1.0, tw, param_twinkle);
        acc += star;
        colAcc += star * depth;
    }
    acc = saturate(acc);
    float mixT = maxN > 1.0 ? colAcc / max(acc, 1e-5) : 0.0;
    float3 col = lerp(param_color_a.rgb, param_color_b.rgb, mixT);
    return float4(col * acc * u_layer_opacity, acc * u_layer_opacity);
}