Shader "FullScreen/Nebula"
{
    Properties
    {
        _SpectrumTexture("SpectrumTexture", 2D) = "white" {}
        _ThemeTexture("ThemeTexture", 2D) = "white" {}
        _SpectrumSize("SpectrumSize", float) = 16

        _Zoom("Zoom", range(-2, 2)) = 0.5
        _Wildness("Wildness", range(1, 10)) = 4.0
        _Brightness("Brightness", range(1, 10)) = 4.0
    }

    HLSLINCLUDE

    // HDRP stuff
    #pragma vertex Vert
    #pragma target 4.5
    #pragma only_renderers d3d11 playstation xboxone xboxseries vulkan metal switch
    #include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/RenderPass/CustomPass/CustomPassCommon.hlsl"

    // here we go...
    sampler2D _SpectrumTexture;
    sampler2D _ThemeTexture;
    float _Zoom;
    float _Wildness;
    float _Brightness;

    // matrix fn
    float2x2 m(float a) {
        float c=cos(a), s=sin(a);
        float2x2 mat = { c, -s, s, c };
        return mat;
    }

    #define iterations 12
    #define formuparam 0.430
    // #define time cos(time*0.2)
    #define volsteps 6
    #define stepsize 0.4

    #define zoom   0.800
    #define tile   0.850
    #define speed  0.05

    #define brightness 0.00015
    #define darkmatter 0.4 // 0.4
    #define distfading 0.960
    #define saturation -14.1

    #define PI = 3.1415926535897932384626433832795;

    float3 mod289(float3 x) {
        return x - floor(x * (1.0 / 289.0)) * 289.0;
    }

    float4 mod289(float4 x) {
        return x - floor(x * (1.0 / 289.0)) * 289.0;
    }

    float4 permute(float4 x) {
             return mod289(((x*34.0)+1.0)*x);
    }

    float4 taylorInvSqrt(float4 r) {
        return 1.79284291400159 - 0.85373472095314 * r;
    }

    float snoise(float3 v)
        {
        const float2  C = float2(1.0/6.0, 1.0/3.0) ;
        const float4  D = float4(0.0, 0.5, 1.0, 2.0);

        // First corner
        float3 i  = floor(v + dot(v, C.yyy) );
        float3 x0 =    v - i + dot(i, C.xxx) ;

        // Other corners
        float3 g = step(x0.yzx, x0.xyz);
        float3 l = 1.0 - g;
        float3 i1 = min( g.xyz, l.zxy );
        float3 i2 = max( g.xyz, l.zxy );

        float3 x1 = x0 - i1 + C.xxx;
        float3 x2 = x0 - i2 + C.yyy; // 2.0*C.x = 1/3 = C.y
        float3 x3 = x0 - D.yyy;           // -1.0+3.0*C.x = -0.5 = -D.y

        // Permutations
        i = mod289(i);
        float4 p = permute( permute( permute(
                             i.z + float4(0.0, i1.z, i2.z, 1.0 ))
                         + i.y + float4(0.0, i1.y, i2.y, 1.0 ))
                         + i.x + float4(0.0, i1.x, i2.x, 1.0 ));

        // Gradients: 7x7 points over a square, mapped onto an octahedron.
        // The ring size 17*17 = 289 is close to a multiple of 49 (49*6 = 294)
        float n_ = 0.142857142857; // 1.0/7.0
        float3    ns = n_ * D.wyz - D.xzx;

        float4 j = p - 49.0 * floor(p * ns.z * ns.z); //  mod(p,7*7)

        float4 x_ = floor(j * ns.z);
        float4 y_ = floor(j - 7.0 * x_ );     // mod(j,N)

        float4 x = x_ *ns.x + ns.yyyy;
        float4 y = y_ *ns.x + ns.yyyy;
        float4 h = 1.0 - abs(x) - abs(y);

        float4 b0 = float4( x.xy, y.xy );
        float4 b1 = float4( x.zw, y.zw );

        float4 s0 = floor(b0)*2.0 + 1.0;
        float4 s1 = floor(b1)*2.0 + 1.0;
        float4 sh = -step(h, float4(0.0, 0.0, 0.0, 0.0));

        float4 a0 = b0.xzyw + s0.xzyw*sh.xxyy ;
        float4 a1 = b1.xzyw + s1.xzyw*sh.zzww ;

        float3 p0 = float3(a0.xy,h.x);
        float3 p1 = float3(a0.zw,h.y);
        float3 p2 = float3(a1.xy,h.z);
        float3 p3 = float3(a1.zw,h.w);

        //Normalise gradients
        //float4 norm = taylorInvSqrt(float4(dot(p0,p0), dot(p1,p1), dot(p2, p2), dot(p3,p3)));
        float4 norm = rsqrt(float4(dot(p0,p0), dot(p1,p1), dot(p2, p2), dot(p3,p3)));
        p0 *= norm.x;
        p1 *= norm.y;
        p2 *= norm.z;
        p3 *= norm.w;

        // Mix final noise value
        float4 m = max(0.6 - float4(dot(x0,x0), dot(x1,x1), dot(x2,x2), dot(x3,x3)), 0.0);
        m = m * m;
        return 42.0 * dot( m*m, float4( dot(p0,x0), dot(p1,x1),
                                                                    dot(p2,x2), dot(p3,x3) ) );
        }

    //////////////////////////////////////////////////////////////

    // PRNG
    // From https://www.shadertoy.com/view/4djSRW
    float prng(in float2 seed) {
        seed = frac(seed * float2 (5.3983, 5.4427));
        seed += dot (seed.yx, seed.xy + float2 (21.5351, 14.3137));
        return frac(seed.x * seed.y * 95.4337);
    }

    //////////////////////////////////////////////////////////////

    float noiseStack(float3 pos,int octaves,float falloff){
        float noise = snoise(float3(pos));
        float off = 1.0;
        if (octaves>1) {
            pos *= 2.0;
            off *= falloff;
            noise = (1.0-off)*noise + off*snoise(float3(pos));
        }
        if (octaves>2) {
            pos *= 2.0;
            off *= falloff;
            noise = (1.0-off)*noise + off*snoise(float3(pos));
        }
        if (octaves>3) {
            pos *= 2.0;
            off *= falloff;
            noise = (1.0-off)*noise + off*snoise(float3(pos));
        }
        return (1.0+noise)/2.0;
    }

    float2 noiseStackUV(float3 pos,int octaves,float falloff,float diff){
        float displaceA = noiseStack(pos,octaves,falloff);
        float displaceB = noiseStack(pos+float3(3984.293,423.21,5235.19),octaves,falloff);
        return float2(displaceA,displaceB);
    }

    float rand(float2 co){
        return frac(sin(dot(co.xy ,float2(12.9898,78.233))) * 43758.5453);
    }

    float circle(in float2 _st, in float _radius){
        float2 dist = _st-float2(0.5, 0.5);
        return 1.-smoothstep(_radius-(_radius*0.01),
                             _radius+(_radius*0.01),
                             dot(dist,dist)*4.0);
    }

    float4 FullScreenPass(Varyings varyings) : SV_Target {
        float depth = LoadCameraDepth(varyings.positionCS.xy);
        PositionInputs posInput = GetPositionInput(varyings.positionCS.xy, _ScreenSize.zw, depth, UNITY_MATRIX_I_VP, UNITY_MATRIX_V);

        float4 fragColor = float4(0.0, 0.0, 0.0, 0.0);
        float time = _Time.y;

        // musique
        float sub = tex2D(_SpectrumTexture, 0.0);
        float bass = tex2D(_SpectrumTexture, 0.25);
        float mids = tex2D(_SpectrumTexture, 0.50);
        float highs = tex2D(_SpectrumTexture, 0.75);
        float4 spectrum = float4(sub, bass, mids, highs);

        // screen
        float zoomFactor = 0.5; // .01 + iMouse.x / iResolution.x;
        float2 uv = float2(posInput.positionNDC.x, 1 - posInput.positionNDC.y) * zoomFactor;
        // float2 uv = (posInput.positionNDC - .5) * zoomFactor;
        float aspect = _ScreenParams.y / _ScreenParams.x;
        uv.y *= aspect;

        // float2 uv= fragCoord.xy/iResolution.xy*zoomFactor-.65;
        // float aspect = iResolution.y/iResolution.x;
        // uv.y*=aspect;
        // p.x *=  _ScreenParams.x / _ScreenParams.y;

        //get coords and direction
        float zoom2 = 0.0 * sin(time);
        float2 c = uv-float2(-0.75*aspect, -0.5*aspect);
        float3 dir=float3(uv-c*zoom2,tan(.3)*1000.0);

        float a2=speed+.5;
        float a1=0.0;
        float2x2 rot1 = { cos(a1), tan(a1), -sin(a1), cos(a1) };
        float2x2 rot2=rot1; //mat2(cos(a2),sin(a2),-sin(a2),cos(a2));
        dir.xz = mul(rot1, dir.xz);
        dir.xy = mul(rot2, dir.xy);

        float3 from = float3(0.,0.,0.);
        float thing = (tan(.15),.152,-2.);
        from += float3(thing, thing, thing);
        from.x -= time * 0.01;

        from.x -= sin(time) * 0.001;
        from.y -= cos(time) * 0.001;

        from.xz = mul(rot1, from.xz);
        from.xy = mul(rot2, from.xy);

        //volumetric rendering
        float s=.4;
        float fade=.2;
        float3 v = float3(0.8, 0.8, 0.8);
        float2 u = float2(0., 0.);
        int r;
        for (r=0; r<volsteps; r++) {
            float3 p=from+s*dir*.5;
            // u = noiseStackUV(float3(0.5),1,0.4,0.1);
            // u = noiseStackUV(0.01*float3(float2(p.x,p.y),30.0*time),1,0.4,0.1);

            p = abs(float3(tile, tile, tile)- (p % float3(tile*2., tile*2., tile*2.))); // tiling fold
            float pa = 0.0;
            float a = 0.0;
            for (int i=0; i<iterations; i++) {
                p=abs(p)/dot(p,p)-formuparam; // the magic formula
                a+=abs(length(p)-pa); // absolute sum of average change
                pa=length(p);
            }
            float dm=max(0.,darkmatter-a*a*tan(.001)); //dark matter
            a*=a*a*2.; // add contrast
            if (r>3) fade*=1.-dm; // dark matter, don't render near
            //v+=float3(dm,dm*.5,0.);

            v+=fade;
            v+=float3(s,s*s,s*s*s*s)*a*brightness*fade; // coloring based on distance
            fade*=distfading; // distance fading
            s+=stepsize;
        }

        v=lerp(length(v), v ,saturation); //color adjust

        float2 vp = uv - 0.5;
        float vl = length(vp)*0.4;
        fragColor = float4(v*.01,1.);
        fragColor.r = 0.0;
        fragColor.g = 0.0;
        fragColor.b *= 1.5;
        fragColor.b = min(0.9, fragColor.b);
        fragColor.b = max(0.3, fragColor.b);
        fragColor += float4(v*.001, 1.);
        fragColor -= float4(float3(vl, vl, vl), 1.0);

        return fragColor;
    }

    ENDHLSL

    SubShader
    {
        Tags{ "RenderPipeline" = "HDRenderPipeline" }
        Pass
        {
            Name "Custom Pass 0"

            ZWrite Off
            ZTest Always
            // Blend SrcAlpha OneMinusSrcAlpha
            Cull Off

            HLSLPROGRAM
                #pragma fragment FullScreenPass
            ENDHLSL
        }
    }
    Fallback Off
}