GLSL图形（二）

precision lowp float;
varying vec2 vUv;
void main(){
    float strength = abs(vUv.x - 0.5) ;
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength =min(abs(vUv.x - 0.5), abs(vUv.y - 0.5));
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength =max(abs(vUv.x - 0.5), abs(vUv.y - 0.5))  ;
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength =step(0.2,max(abs(vUv.x - 0.5), abs(vUv.y - 0.5)))   ;
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength =1.0-step(0.2,max(abs(vUv.x - 0.5), abs(vUv.y - 0.5)))   ;
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength = floor(vUv.x*10.0)/10.0;
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength = floor(vUv.y*10.0)/10.0;
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength = floor(vUv.x*10.0)/10.0*floor(vUv.y*10.0)/10.0;
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength = ceil(vUv.x*10.0)/10.0*ceil(vUv.y*10.0)/10.0;
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
float random (vec2 st) {
    return fract(sin(dot(st.xy,vec2(12.9898,78.233)))*43758.5453123);
}
void main(){
     float strength = random(vUv);
     gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
float random (vec2 st) {
    return fract(sin(dot(st.xy,vec2(12.9898,78.233)))*43758.5453123);
}
void main(){
    float strength = ceil(vUv.x*10.0)/10.0*ceil(vUv.y*10.0)/10.0;
    strength = random(vec2(strength,strength));
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength = length(vUv);
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
    float strength =1.0 - distance(vUv,vec2(0.5,0.5));
    gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
     float strength = 1.0 - step(0.5,distance(vUv,vec2(0.5))+0.25) ;
     gl_FragColor =vec4(strength,strength,strength,1);
}

precision lowp float;
varying vec2 vUv;
void main(){
     float strength = step(0.5,distance(vUv,vec2(0.5))+0.35) ;
     strength *= (1.0 - step(0.5,distance(vUv,vec2(0.5))+0.25)) ;
     gl_FragColor =vec4(strength,strength,strength,1);

}

precision lowp float;
varying vec2 vUv;
void main(){
     float strength =  abs(distance(vUv,vec2(0.5))-0.25) ;
     gl_FragColor =vec4(strength,strength,strength,1);

}