1.随机雪花

float random (vec2 st) 
{
    return fract(sin(dot(st.xy,
    vec2(12.9898,78.233)))*
    43758.5453123);
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = (fragCoord.xy - 0.5 * iResolution.xy) / iResolution.y;
    float c1 = random(uv);
    fragColor = vec4(c1 * vec3(1.0,1.0,0.0),1.0);
}

效果:

2:放大和取整

float random (vec2 st) 
{
    return fract(sin(dot(st.xy,
    vec2(12.9898,78.233)))*
    43758.5453123);
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = (fragCoord.xy - 0.5 * iResolution.xy) / iResolution.y;
    uv *= 10.0;
    //放大和取整
    uv = floor(uv);
    float c1 = random(uv);
    fragColor = vec4(c1 * vec3(1.0,1.0,0.0),1.0);
}

效果:

3.fract 后的颜色变化

float random (vec2 st) 
{
    return fract(sin(dot(st.xy,
    vec2(12.9898,78.233)))*
    43758.5453123);
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = (fragCoord.xy - 0.5 * iResolution.xy) / iResolution.y;
    uv *= 10.0;
    //放大和取整
    uv = fract(uv);
    //float c1 = random(uv);
    vec3 c2 = vec3(uv,0.0);
    fragColor = vec4(c2 * vec3(1.0,1.0,0.0),1.0);
}

效果: