snowflake_sm4.hlsl.h

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#define SRC(...) #__VA_ARGS__
SRC(
struct UBO
{
 float4x4 modelViewProj;
 float2 OutputSize;
 float time;
};
uniform UBO global;

float4 VSMain(float4 position : POSITION, float2 texcoord : TEXCOORD0) : SV_POSITION
{
 return mul(global.modelViewProj, position);
}


static const float atime = (global.time + 1.0) / 4.0;

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

float rand_float(float x)
{
 return rand(float2(x, 1.0));
}

float snow(float3 pos, float2 uv, float o)
{
 float2 d = (pos.xy - uv);
 float a = atan(d.y / d.x) + sin(atime*1.0 + o) * 10.0;

 float dist = d.x*d.x + d.y*d.y;

 if(dist < pos.z/400.0)
 {
 float col = 0.0;
 if(sin(a * 8.0) < 0.0)
 {
 col=1.0;
 }
 if(dist < pos.z/800.0)
 {
 col+=1.0;
 }
 return col * pos.z;
 }

 return 0.0;
}

float col(float2 c)
{
 float color = 0.0;
 for (int i = 1; i < 15; i++)
 {
 float o = rand_float(float(i) / 3.0) * 15.0;
 float z = rand_float(float(i) + 13.0);
 float x = 1.8 - (3.6) * (rand_float(floor((global.time*((z + 1.0) / 2.0) +o) / 2.0)) + sin(global.time * o /1000.0) / 10.0);
 float y = 1.0 - fmod((global.time * ((z + 1.0)/2.0)) + o, 2.0);

 color += snow(float3(x,y,z), c, o);
 }

 return color;
}

float4 PSMain(float4 position : SV_POSITION) : SV_TARGET
{
 float2 uv = position.xy / global.OutputSize.xy;
 uv = uv * 2.0 - 1.0;
 float2 p = uv;
 p.x *= global.OutputSize.x / global.OutputSize.y;
 p.y =- p.y;

 float c = col(p);
 return float4(c,c,c,c);
};
)