Shader-Texture not seamlessly tileable?

shader_effects["Wolkenmaske"] = {shader=basic_fsh..[[ 



uniform float daytime; 



const vec2 ar = vec2(1.6, 0.9); //ASPECT RATIO 

float cloudspeed = 0.0075; 

vec2 cloudsize = vec2(0.33); 

float cloudsoftness = 2.3-texcoord.x*2; 

vec2 cloudmoveA = vec2(0.5, 0.0) * time * cloudspeed; 

vec2 cloudmoveB = vec2(-0.2, 0.0) * time * cloudspeed; 



vec2 Versatz = vec2(0.75,0.75);



void main() 

{ 

 vec2 uv = cloudsize * texcoord.xy; 

 vec4 colA = texture2D(iChannel0, fract(vec2(1.00) * uv.xy +cloudmoveA ) ); 

 vec4 colB = texture2D(iChannel0, fract(vec2(1.11) * uv.xy +cloudmoveB +Versatz ) );

 

//ALTERNATIVELY CLAMP TEXTURE-COORDINATES -- very imperfect workaround...

// vec4 colA = texture2D(iChannel0, clamp( fract( vec2(1.00) * uv.xy +cloudmoveA ) ,0.0,0.99928) );

// vec4 colB = texture2D(iChannel0, clamp( fract( vec2(1.11) * uv.xy +cloudmoveB +Versatz ) ,0.0,0.99928) );

 

 float wolkentransparenz = ((1.0+cos(daytime*0.5*3.142)) ); 



 float subtraction = clamp(colA.r-colB.r, 0.0, 1.0) * wolkentransparenz; 

 vec4 finalColor = vec4( vec3(1.0) , pow( subtraction , cloudsoftness) ); 



 float w = (0.75 - texcoord.x) *4; 

 float h = ( (daytime-0.21) - texcoord.y) *1; 

 float Sun = 2* pow( 1.0 - clamp( (sqrt(pow(w,2)+pow(h,2))/(0.5)), 0.0,1.0) , 10); 

 finalColor.a = abs(finalColor.a - Sun); 

  

 gl_FragColor = finalColor; 

} 

]]} 



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local eff="Wolkenmaske" 

local obj = "TestClouds" 

local id = 2 



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shaderAddEffect(eff) 

shaderRemoveEffect(eff) 

shader_effects[eff].num.strength=1 

bind(eff, "time", field("shader_iTime")) 

bind(eff, "daytime", field("Values.Daytime.Int")); 

function updateWeltbildsonne() 

 shader_effects[eff].num.daytime = Values.Daytime.Int * 0.0125; 

end 

shaderSetOptions({{shader = shader_effects[eff].num(), comp_dst=5, comp_src=4 }}, id) 

Objects[obj].ShaderSet = id 



registerEventHandler("mainLoop", "updateWeltbildsonne") 

local eff = "Daynight"
shader_effects[eff] = { shader = Shaders[eff].Compiled }
shaderAddEffect(eff)
bind(eff, "daytime", field("getTime() * 0.00125"))