ttrpg-tools/src/components/utils/3mf-generator.ts

import * as THREE from "three";
import { exportTo3MF } from "three-3mf-exporter";
import type { TraceResult } from "./image-tracer";
import {Vector3} from "three";

export interface ExtrusionSettings {
  size: number; // 模型整体尺寸 (mm)
  layers: Array<{
    id: string;
    thickness: number; // 图层厚度 (mm)
  }>;
}

export interface LayerMesh {
  id: string;
  mesh: THREE.Mesh;
  thickness: number;
  color: number;
}

/**
 * 从图层索引生成颜色（使用黄金角确保颜色分散）
 */
function generateLayerColor(index: number): number {
  const hue = (index * 137.508) % 360; // 黄金角
  return new THREE.Color(`hsl(${hue}, 70%, 50%)`).getHex();
}

/**
 * 将矢量路径生成 3MF 文件
 * @param image - 原始图片
 * @param traceResult - 矢量追踪结果
 * @param settings - 挤压设置
 * @returns 3MF Blob
 */
export async function generate3MF(
  image: HTMLImageElement,
  traceResult: TraceResult,
  settings: ExtrusionSettings
): Promise<Blob> {
  // 创建 Three.js 场景
  const scene = new THREE.Scene();

  // 计算缩放比例，使模型适应指定尺寸
  const maxDimension = Math.max(traceResult.width, traceResult.height);
  const scale = settings.size / maxDimension;

  // 中心偏移
  const offsetX = -traceResult.width / 2;
  const offsetY = -traceResult.height / 2;

  // 为每个启用的图层创建网格
  let currentHeight = 0;
  const meshes: LayerMesh[] = [];
  let layerIndex = 0;

  let boundingBox = new THREE.Box3();
  for (const layerSetting of settings.layers) {
    const layer = traceResult.layers.find((l) => l.id === layerSetting.id);
    if (!layer) continue;

    // 创建挤压几何体
    const extrudeSettings: THREE.ExtrudeGeometryOptions = {
      depth: layerSetting.thickness,
      curveSegments: 36,
      bevelEnabled: true,
      bevelSize: 0.4
    };
    const geometry: THREE.ExtrudeGeometry = new THREE.ExtrudeGeometry(layer.paths, extrudeSettings);
    geometry.computeBoundingBox();

    // 为该图层生成颜色
    const color = generateLayerColor(layerIndex);
    const material = new THREE.MeshStandardMaterial({
      color,
      metalness: 0.3,
      roughness: 0.7,
    });

    const mesh = new THREE.Mesh(geometry, material);
    boundingBox.expandByObject(mesh);

    // 设置图层高度（堆叠）
    mesh.position.y = currentHeight;

    scene.add(mesh);
    meshes.push({
      id: layerSetting.id,
      mesh,
      thickness: layerSetting.thickness,
      color,
    });

    currentHeight += layerSetting.thickness;
    layerIndex++;
  }

  const center = boundingBox.getCenter(new Vector3());
  for(const mesh of meshes){
      mesh.mesh.position.sub(center);
  }

  if (meshes.length === 0) {
    throw new Error("没有可生成的图层");
  }

  // 导出为 3MF
  const data = await exportTo3MF(scene);
  const blob = new Blob([data], { type: "model/3mf" });

  // 清理
  scene.clear();
  meshes.forEach(({ mesh }) => {
    mesh.geometry.dispose();
    (mesh.material as THREE.Material).dispose();
  });

  return blob;
}