Texture variation for unreal engine 4

variations.hlsl

#define USEHASH

struct Functions
{
    float4 hash4( float2 p ) { return frac(sin(float4( 1.0+dot(p,float2(37.0,17.0)), 
                                                  2.0+dot(p,float2(11.0,47.0)),
                                                  3.0+dot(p,float2(41.0,29.0)),
                                                  4.0+dot(p,float2(23.0,31.0))))*103.0); }

    float4 textureNoTile(Texture2D iChannel0, SamplerState iChannel0Sampler, in float2 uv, Texture2D iChannel1, SamplerState iChannel1Sampler)
    {
        float2 iuv = floor( uv );
        float2 fuv = frac( uv );

    #ifdef USEHASH    
        // generate per-tile transform (needs GL_NEAREST_MIPMAP_LINEARto work right)
        float4 ofa = Texture2DSample( iChannel1, iChannel1Sampler, (iuv + float2(0.5,0.5))/256.0 );
        float4 ofb = Texture2DSample( iChannel1, iChannel1Sampler, (iuv + float2(1.5,0.5))/256.0 );
        float4 ofc = Texture2DSample( iChannel1, iChannel1Sampler, (iuv + float2(0.5,1.5))/256.0 );
        float4 ofd = Texture2DSample( iChannel1, iChannel1Sampler, (iuv + float2(1.5,1.5))/256.0 );
    #else
        // generate per-tile transform
        float4 ofa = hash4( iuv + float2(0.0,0.0) );
        float4 ofb = hash4( iuv + float2(1.0,0.0) );
        float4 ofc = hash4( iuv + float2(0.0,1.0) );
        float4 ofd = hash4( iuv + float2(1.0,1.0) );
    #endif
        
        float2 ddx = DDX( uv );
        float2 ddy = DDY( uv );

        // transform per-tile uvs
        ofa.zw = sign(ofa.zw-0.5);
        ofb.zw = sign(ofb.zw-0.5);
        ofc.zw = sign(ofc.zw-0.5);
        ofd.zw = sign(ofd.zw-0.5);
        
        // uv's, and derivarives (for correct mipmapping)
        float2 uva = uv*ofa.zw + ofa.xy; float2 ddxa = ddx*ofa.zw; float2 ddya = ddy*ofa.zw;
        float2 uvb = uv*ofb.zw + ofb.xy; float2 ddxb = ddx*ofb.zw; float2 ddyb = ddy*ofb.zw;
        float2 uvc = uv*ofc.zw + ofc.xy; float2 ddxc = ddx*ofc.zw; float2 ddyc = ddy*ofc.zw;
        float2 uvd = uv*ofd.zw + ofd.xy; float2 ddxd = ddx*ofd.zw; float2 ddyd = ddy*ofd.zw;
            
        // fetch and blend
        float2 b = smoothstep(0.25,0.75,fuv);
        
        return lerp( lerp( iChannel0.SampleGrad( iChannel0Sampler, uva, ddxa, ddya ), 
                         iChannel0.SampleGrad( iChannel0Sampler, uvb, ddxb, ddyb ), b.x ), 
                    lerp( iChannel0.SampleGrad( iChannel0Sampler, uvc, ddxc, ddyc ),
                         iChannel0.SampleGrad( iChannel0Sampler, uvd, ddxd, ddyd ), b.x), b.y );
    }
};

Functions func;


//float2 uv = fragCoord / iResolution.x;

float f = smoothstep( 0.4, 0.6, sin(iTime    ) );
float s = smoothstep( 0.4, 0.6, sin(iTime*0.5) );

uv = 16 * uv;//(4.0 + 16.0*s)*uv + iTime*0.1;

float3 cola = func.textureNoTile( iChannel0, iChannel0Sampler, uv, iChannel1, iChannel1Sampler).xyz;
float3 colb = Texture2DSample( iChannel0, iChannel0Sampler, uv ).xyz;

float3 col = lerp( cola, colb, f );

return float4( cola, 1.0 );