AE影视后期特效全栈解析：遮罩、调色、抠像、MG动画、3D与Vlog制作的工程化实践

B(t) = (1-t)²P₀ + 2t(1-t)P₁ + t²P₂,  t∈[0,1]

// 应用于Mask Path的表达式（需启用"表达式控制"）
const targetLayer = thisComp.layer("背景");
const samplePoint = targetLayer.transform.position;
const brightness = targetLayer.sampleImage(samplePoint, [0.5,0.5], true, 1).r;
const scaleFactor = linear(brightness, 0, 1, 0.8, 1.2);
const originalPath = thisProperty.value;
const newVerts = originalPath.vertices.map(p => p * scaleFactor);
createPath(newVerts, originalPath.inTangents, originalPath.outTangents, originalPath.isClosed);

// 效果："Set Matte" -> "Matte Layer" 属性
const matteName = thisComp.layer("索引控制").effect("Slider")("滑块").value;
thisComp.layer(matteName).index;

// 在"颜色阈值"效果的"阈值"属性上写入：
const src = thisComp.layer("原始").sampleImage(transform.position, [0.1,0.1]);
const gray = 0.299*src.r + 0.587*src.g + 0.114*src.b;
if (gray > 0.5) 1 else 0;  // 生成硬边遮罩

// 在"色彩平衡"效果中，对每个通道应用分段函数
// 红色通道修正曲线（S型）
const x = thisComp.layer("原始").sampleImage(transform.position, [0,0]).r;
const a = 0.2; // 暗部压缩
const b = 0.8; // 亮部扩展
const y = (x - a) / (b - a);
clamp(y, 0, 1);

// .jsx脚本，运行于ExtendScript
app.project.colorDepth = 32; // 浮点
app.project.workingSpace = "ACES - ACEScg";
app.project.linearizeWorkingSpace = true;
// 遍历所有合成，开启线性化
for (var i = 1; i <= app.project.numItems; i++) {
  var item = app.project.item(i);
  if (item instanceof CompItem) {
    item.linearBlending = true;
  }
}

// 色相补偿：取抠像主色（如绿幕）的色相反向
const keyColor = [0.33, 1, 0.5]; // HSV 绿色
const compHue = (keyColor[0] + 0.5) % 1.0;
[compHue, 0.8, 0.6] // 输出给"色相/饱和度"的"色相偏移"

// 在Keylight的"Screen Gain"属性上
const avgLum = thisComp.layer("背景").sampleImage([960,540], [100,100]).r;
linear(avgLum, 0.2, 0.8, 80, 120);

// 自定义溢出抑制——在"颜色校正"->"色阶"中操作
const src = sampleImage(transform.position, [0.5,0.5]);
const green = src.g;
const red = src.r;
// 若绿色通道过度主导，则压制G并补偿R
if (green > 0.6 && green > red) {
  const spill = (green - 0.6) * 0.8;
  [src.r + spill*0.3, src.g - spill, src.b + spill*0.1]
} else src;

// Matte Choker的"Choke"属性根据画面噪点自动调节
const noise = thisComp.layer("噪点参考").effect("噪点H")("滑块");
linear(noise, 0, 10, 0.5, 2.0);

// 应用于位置属性
const target = thisComp.layer("控制空对象").transform.position;
const freq = 3.0;  // 频率
const decay = 0.85; // 阻尼
const t = time - inPoint;
const offset = target.valueAtTime(inPoint) - target.valueAtTime(time);
const amp = length(offset);
const phase = Math.atan2(offset[1], offset[0]);
const x = amp * Math.sin(freq * t * 2*Math.PI) * Math.exp(-decay * t);
[ target[0] + x * Math.cos(phase), target[1] + x * Math.sin(phase) ]

// 生成N个圆形，位置分布在斐波那契螺旋上
var comp = app.project.activeItem;
if (comp && comp instanceof CompItem) {
  var num = 50;
  for (var i = 0; i < num; i++) {
    var shape = comp.layers.addShape();
    var group = shape.property("ADBE Root Vectors Group").addProperty("ADBE Vector Group");
    var ellipse = group.property("ADBE Vectors Group").addProperty("ADBE Vector Shape - Ellipse");
    var pos = group.property("ADBE Vector Transform Group").property("ADBE Vector Transform Position");
    var phi = Math.PI * (1 + Math.sqrt(5)) * i;
    var radius = 5 * Math.sqrt(i);
    pos.setValue([400 + radius * Math.cos(phi), 300 + radius * Math.sin(phi)]);
    // 随机颜色
    var fill = group.property("ADBE Vectors Group").addProperty("ADBE Vector Fill");
    fill.property("ADBE Vector Fill Color").setValue([Math.random(), Math.random(), Math.random()]);
  }
}

// 文本图层的"源文本"属性
var data = footage("data.json").sourceData;
var index = Math.floor(time / 0.5) % data.length;
"当前数值: " + data[index].value + "\n状态: " + data[index].status;

// 在Null的"位置"属性上
const trackPoint = thisComp.layer("3D追踪点").transform.position;
const cam = thisComp.activeCamera;
// 将追踪点从世界坐标转为屏幕坐标（用于2D叠加）
cam.fromWorld(trackPoint);

// 光圈大小 = 根据目标物体距离自动调整
const targetZ = thisComp.layer("焦点物体").transform.position[2];
const camZ = thisComp.activeCamera.transform.position[2];
const dist = Math.abs(targetZ - camZ);
linear(dist, 0, 500, 1.4, 16); // 光圈值f-stop

// 平行光"强度"属性根据合成中所有3D图层的平均亮度自动调整
var total = 0, count = 0;
for (var i = 1; i <= thisComp.numLayers; i++) {
  var l = thisComp.layer(i);
  if (l.hasTrackMatte) continue;
  var samp = l.sampleImage([0.5,0.5], [0.1,0.1]);
  total += (samp.r + samp.g + samp.b)/3;
  count++;
}
(total / count) * 200; // 映射到光照强度

// 缩放属性的表达式
const audio = thisComp.layer("背景音乐").effect("Both Channels")("Slider");
const amp = audio.valueAtTime(time) * 100;
const base = 100;
base + amp * 0.5;

// 色温偏移量自动匹配参考帧
const ref = thisComp.layer("色卡参考").sampleImage([0.5,0.5], [0.1,0.1]);
const current = thisComp.layer("当前片段").sampleImage([0.5,0.5], [0.1,0.1]);
const deltaR = ref.r - current.r;
const deltaB = ref.b - current.b;
[deltaR*10, 0, deltaB*10] // 输出给"颜色平衡"的偏移量

// 添加渲染队列并设置输出模块
var comp = app.project.activeItem;
var rend = app.project.renderQueue.add(comp);
var outMod = rend.outputModule(1);
outMod.applyTemplate("H.264 - 1080p 30fps");
outMod.file = new File("~/Desktop/output_" + comp.name + ".mp4");
// 设置起始帧
rend.timeSpanStart = 0;
rend.timeSpanDuration = comp.duration * comp.frameRate;
app.project.renderQueue.render();

posterizeTime(1 / 10); // 每秒只计算10次，降低CPU负载
sampleImage(transform.position, [0.5,0.5]);

// 自动替换所有缺失素材
var items = app.project.items;
for (var i = 1; i <= items.length; i++) {
  if (items[i] instanceof FootageItem && !items[i].exists) {
    var newPath = items[i].name.replace("_RAW", "_PROXY");
    items[i].replace(new File(newPath));
  }
}

try {
  // 可能出错的运算
  var result = 1 / (time - 5);
  result;
} catch (e) {
  console.log("Error at time " + time + ": " + e.message);
  0; // 安全默认值
}