【SHADER】Shader实例学习1：UI noise halo

Shader实例学习1：UI noise halo

简介
- 源码注释
- 关键步骤
- 总结

简介

又换方向做图形相关的工作了，门槛确实有一点，数学、图形什么的都要学，算轨迹用到力学什么的也是基本操作。大力出奇迹，跟着shadertoy里的众多大神学起来。本篇学习内容来自于:

UI noise halo

源码注释

// noise from https://www.shadertoy.com/view/4sc3z2
vec3 hash33(vec3 p3)
{p3 = fract(p3 * vec3(.1031,.11369,.13787));p3 += dot(p3, p3.yxz+19.19);return -1.0 + 2.0 * fract(vec3(p3.x+p3.y, p3.x+p3.z, p3.y+p3.z)*p3.zyx);
}
// 随机数
float snoise3(vec3 p)
{const float K1 = 0.333333333;const float K2 = 0.166666667;vec3 i = floor(p + (p.x + p.y + p.z) * K1);vec3 d0 = p - (i - (i.x + i.y + i.z) * K2);vec3 e = step(vec3(0.0), d0 - d0.yzx);vec3 i1 = e * (1.0 - e.zxy);vec3 i2 = 1.0 - e.zxy * (1.0 - e);vec3 d1 = d0 - (i1 - K2);vec3 d2 = d0 - (i2 - K1);vec3 d3 = d0 - 0.5;vec4 h = max(0.6 - vec4(dot(d0, d0), dot(d1, d1), dot(d2, d2), dot(d3, d3)), 0.0);vec4 n = h * h * h * h * vec4(dot(d0, hash33(i)), dot(d1, hash33(i + i1)), dot(d2, hash33(i + i2)), dot(d3, hash33(i + 1.0)));return dot(vec4(31.316), n);
}vec4 extractAlpha(vec3 colorIn)
{vec4 colorOut;float maxValue = min(max(max(colorIn.r, colorIn.g), colorIn.b), 1.0);if (maxValue > 1e-5){colorOut.rgb = colorIn.rgb * (1.0 / maxValue);colorOut.a = maxValue;}else{colorOut = vec4(0.0);}return colorOut;
}#define BG_COLOR (vec3(sin(iTime)*0.5+0.5) * 0.0 + vec3(0.0))
#define time iTime
const vec3 color1 = vec3(0.611765, 0.262745, 0.996078);
const vec3 color2 = vec3(0.298039, 0.760784, 0.913725);
const vec3 color3 = vec3(0.062745, 0.078431, 0.600000);
const float innerRadius = 0.6;
const float noiseScale = 0.65;float light1(float intensity, float attenuation, float dist)
{return intensity / (1.0 + dist * attenuation);
}
float light2(float intensity, float attenuation, float dist)
{return intensity / (1.0 + dist * dist * attenuation);
}void draw( out vec4 _FragColor, in vec2 vUv )
{vec2 uv = vUv;float ang = atan(uv.y, uv.x);float len = length(uv);float v0, v1, v2, v3, cl;float r0, d0, n0;float r, d;// ring// 生成随机数n0 = snoise3( vec3(uv * noiseScale, time * 0.5) ) * 0.5 + 0.5;// 动态变化的圆半径，呈现呼吸感，这个是灵魂r0 = mix(mix(innerRadius, 1.0, 0.4), mix(innerRadius, 1.0, 0.6), n0);// 与圆边界的距离. r0==len时为0d0 = distance(uv, r0 / len * uv);// 光线(颜色)随距离(距离圆边界)变化v0 = light1(1.0, 10.0, d0);// 裁掉 r0*1.05 距离外的颜色v0 *= smoothstep(r0 * 1.05, r0, len);// 颜色混合参数，根据时间变化cl = cos(ang + time * 2.0) * 0.5 + 0.5;// high light// 控制高亮光线顺时针变化float a = time * -1.0;// 当前高亮位置的坐标vec2 pos = vec2(cos(a), sin(a)) * r0;// 与高亮位置的距离d = distance(uv, pos);// 光线衰减，环形v1 = light2(1.5, 5.0, d);// 光线衰减，距离边界。(沿边界快速衰减)v1 *= light1(1.0, 50.0 , d0);// back decay// 实心圆v2 = smoothstep(1.0, mix(innerRadius, 1.0, n0 * 0.5), len);// hole// 圆环v3 = smoothstep(innerRadius, mix(innerRadius, 1.0, 0.5), len);// color//vec3 c = mix(color1, color2, cl);// 根据时间变化的颜色值vec3 col = mix(color1, color2, cl);// 随距离与color3颜色混合col = mix(color3, col, v0);// 高亮，交集圆环col = (col + v1) * v2 * v3 ;//col.rgb = clamp(col.rgb, 0.0, 1.0);// 调整颜色，同时将原色中rgb中最大的值作为alpha，后续作为颜色融合的参数.// 经过试验：没有这一步以及后面的颜色混合，效果也跟最终效果差不多，从前面的代码逻辑也可以看出// 如果有这一步，因为extractAlpha函数内部对rgb做了放大，反而后面必须跟mix,相当于是个逆操作_FragColor = extractAlpha(col);
}// 入口函数
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{// 变换到[-1,1]范围的坐标系。(注意除的是界面x y轴短的那根轴)vec2 uv = (fragCoord*2.-iResolution.xy)/iResolution.y;vec4 col;draw(col, uv);vec3 bg = BG_COLOR;// 这里用到一个小技巧，使用col.a作为颜色融合的参数// 颜色融合，否则背景、前景界限明显fragColor.rgb = mix(bg, col.rgb, col.a); //normal blend
}