curpos += rd * exp(0.01 * i) * stepsize;

        #define NUM_STEPS 128float hash(float3 p)
{p = frac(p * 0.3183099 + 0.1);p *= 17.0;return frac(p.x * p.y * p.z * (p.x + p.y + p.z));
}float Noise(in float3 x)
{float3 p = floor(x);float3 f = frac(x);f = f * f * (3.0 - 2.0 * f);return lerp(lerp(lerp( hash(p + float3(0,0,0)), hash(p + float3(1,0,0)),f.x),lerp( hash(p + float3(0,1,0)), hash(p + float3(1,1,0)),f.x),f.y),lerp(lerp( hash(p + float3(0,0,1)), hash(p + float3(1,0,1)),f.x),lerp( hash(p + float3(0,1,1)), hash(p + float3(1,1,1)),f.x),f.y),f.z);
}float map5(in float3 p)
{float3 q = p;float f = 0.0f;f  = 0.50000 * Noise( q );q = q * 2.02;f += 0.25000 * Noise( q );q = q * 2.03;f += 0.12500 * Noise( q );q = q * 2.01;f += 0.06250 * Noise( q );q = q * 2.02;f += 0.03125 * Noise( q );return clamp(f, 0.0, 1.0);
}float map3( in float3 p )
{float3 q = p;float f = 0.0f;f  = 0.50000 * Noise( q );q = q * 2.02;f += 0.25000 * Noise( q );q = q * 2.03;f += 0.12500 * Noise( q );return clamp(f, 0.0, 1.0);
}//origin       : Ray origin position
// dir          : Ray direction
//spherePos     : Sphere center position
//sphere Rad    ： Sphere radius
float intersectSphere(float3 origin, float3 dir, float3 spherePos, float sphereRad)
{float3 oc = origin - spherePos;float b = 2.0 * dot(dir, oc);float c = dot(oc, oc) - sphereRad * sphereRad;float disc = b * b - 4.0 * c;if (disc < 0.0)return -1.0;    float q = (-b + ((b < 0.0) ? -sqrt(disc) : sqrt(disc))) / 2.0;float t0 = q;float t1 = c / q;if (t0 > t1) {float temp = t0;t0 = t1;t1 = temp;}if (t1 < 0.0)return 0.0;return (t0 < 0.0) ? t1 : t0;
}float Lighting(float3 ro, float3 rd, float3 curpos)
{   float en = 0.0f;float3 L = float3(1, 1, 1);float3 lightpos = curpos;float lightstepsize = 0.9;float lightden = 0;float cos = dot(L, rd);float g = 0.3;float hen = (1- g*g) / pow((1 + g*g - 2 * g * cos), 3/2) / (4 * 3.1415);hen *= 1.5;for(int i = 0; i < 4; i++){lightden = map3(lightpos * 0.002);lightpos += L * lightstepsize * exp(0.01 * i);}//hen *= 2 * exp(-lightden) * (1 - 2 * exp(2 * lightstepsize * 4));en = exp(- 1.2 * lightden * i);en = smoothstep(0.01, 0.99, en);return en * hen;
}float4 mainImage(float2 fragCoord, float2 iResolution, float iTime, float3 rd, float3 ro, float3 wpos, Texture2D remap, SamplerState remapSampler)
{float4 Output = float4(0, 0, 0, 1);float stepsize = 3;//iTime *= 0.01;float TransToNoiseSpace = 0.001;ro *= TransToNoiseSpace;float t = intersectSphere(ro, rd, float3(0, 0, -99000), 100000);float3 curpos = ro + rd * t;curpos += float3(iTime, 0, 0);float4 col = float4(0, 0, 0, 0);for(int i = 0; i < NUM_STEPS; i++){if(curpos.z < 30) break;//step size distance functionfloat dens = map5(curpos * 0.002);dens = smoothstep(0.4, 0.55, dens);float3 pos = curpos;float T = Lighting(ro, rd, curpos);col.rgb += dens * 0.2 * (exp(-0.01 * i) + 1);col.a += T * 0.005;curpos += rd * exp(0.01 * i) * stepsize;}//col = pow(col, 15);//Output.rgb = lerp(float3(0.4,0.6,0.8), col.rgb * 10 , col.r);Output.rgb = col.rgb * col.a;return Output;
}//return  mainImage(fragCoord, iResolution, iTime, rd, ro, wpos, remap, remapSampler);// fragCoord
// iResolution
// iTime
// rd
// ro
// wpos
// remap