fix: separate component solids in STEP output

lib/index.ts

@@ -55,7 +55,7 @@ export interface CircuitJsonToStepOptions {
   boardThickness?: number
   /** Product name (default: "PCB") */
   productName?: string
-  /** Include component meshes (default: false) */
+  /** Include component meshes (default: true) */
   includeComponents?: boolean
   /** Include external model meshes from model_*_url fields (default: false). Only applicable when includeComponents is true. */
   includeExternalMeshes?: boolean
@@ -86,6 +86,7 @@ export async function circuitJsonToStep(
   const boardWidth = options.boardWidth ?? pcbBoard?.width
   const boardHeight = options.boardHeight ?? pcbBoard?.height
   const boardThickness = options.boardThickness ?? pcbBoard?.thickness ?? 1.6
+  const includeComponents = options.includeComponents ?? true
   const productName = options.productName ?? "PCB"
 
   // Get board center position (defaults to 0, 0 if not specified)
@@ -568,7 +569,7 @@ export async function circuitJsonToStep(
   let handledComponentIds = new Set<string>()
   let handledPcbComponentIds = new Set<string>()
 
-  if (options.includeComponents && options.includeExternalMeshes) {
+  if (includeComponents && options.includeExternalMeshes) {
     const mergeResult = await mergeExternalStepModels({
       repo,
       circuitJson,
@@ -582,7 +583,7 @@ export async function circuitJsonToStep(
 
   // Generate component mesh fallback if requested
   // Only call mesh generation if there are components that need it
-  if (options.includeComponents) {
+  if (includeComponents) {
     // Build set of pcb_component_ids covered by cad_components with model_step_url
     const pcbComponentIdsWithStepUrl = new Set<string>()
     for (const item of circuitJson) {

lib/mesh-generation.ts

@@ -327,44 +327,47 @@ export async function generateComponentMeshes(
       renderBoardTextures: false,
     })
 
-    // Extract or generate triangles from component boxes
-    const allTriangles: GLTFTriangle[] = []
-    for (const box of scene3d.boxes) {
+    // Process each component box as a separate STEP solid.
+    // STEP requires each ManifoldSolidBrep to have a closed, watertight
+    // boundary — merging triangles from multiple disconnected boxes into
+    // one ClosedShell produces an invalid solid that viewers silently drop.
+    for (let i = 0; i < scene3d.boxes.length; i++) {
+      const box = scene3d.boxes[i]
+
+      let boxTriangles: GLTFTriangle[]
       if (box.mesh && "triangles" in box.mesh) {
-        allTriangles.push(...box.mesh.triangles)
+        boxTriangles = box.mesh.triangles
       } else {
-        // Generate simple box mesh for this component
-        const boxTriangles = createBoxTriangles(box)
-        allTriangles.push(...boxTriangles)
+        boxTriangles = createBoxTriangles(box)
       }
-    }
 
-    // Create STEP faces from triangles if we have any
-    if (allTriangles.length > 0) {
-      // Transform triangles from GLTF XZ plane (Y=up) to STEP XY plane (Z=up)
-      const transformedTriangles = allTriangles.map((tri) => ({
+      if (boxTriangles.length === 0) continue
+
+      // Transform from GLTF coordinate system (Y-up) to STEP (Z-up)
+      const transformedTriangles = boxTriangles.map((tri) => ({
         vertices: tri.vertices.map((v) => ({
           x: v.x,
           y: v.z, // GLTF Z becomes STEP Y
           z: v.y, // GLTF Y becomes STEP Z
         })),
         normal: {
           x: tri.normal.x,
-          y: tri.normal.z, // GLTF Z becomes STEP Y
-          z: tri.normal.y, // GLTF Y becomes STEP Z
+          y: tri.normal.z,
+          z: tri.normal.y,
         },
       }))
+
       const componentFaces = createStepFacesFromTriangles(
         repo,
         transformedTriangles as any,
       )
 
-      // Create closed shell and solid for components
       const componentShell = repo.add(
         new ClosedShell("", componentFaces as any),
       )
+      const componentName = (box as any).name || `Component_${i + 1}`
       const componentSolid = repo.add(
-        new ManifoldSolidBrep("Components", componentShell),
+        new ManifoldSolidBrep(componentName, componentShell),
       )
       solids.push(componentSolid)
     }

test/basics/separate-solids/separate-solids.test.ts

@@ -0,0 +1,50 @@
+import { test, expect } from "bun:test"
+import { circuitJsonToStep } from "../../../lib/index"
+import { importStepWithOcct } from "../../utils/occt/importer"
+import circuitJson from "../basics04/basics04.json"
+
+test("separate-solids: each component gets its own ManifoldSolidBrep", async () => {
+  const stepText = await circuitJsonToStep(circuitJson as any, {
+    includeComponents: true,
+    productName: "SeparateSolidsTest",
+  })
+
+  // Verify STEP format
+  expect(stepText).toContain("ISO-10303-21")
+  expect(stepText).toContain("END-ISO-10303-21")
+
+  // Count ManifoldSolidBrep entries — should be at least 3:
+  // 1 for the board + 1 per component (2 components in basics04)
+  const solidMatches = stepText.match(/MANIFOLD_SOLID_BREP\s*\(\s*'([^']*)'/g) || []
+  const solidNames = solidMatches.map((m) => {
+    const nameMatch = m.match(/MANIFOLD_SOLID_BREP\s*\(\s*'([^']*)'/)
+    return nameMatch?.[1] ?? ""
+  })
+
+  console.log(`  Solids found (${solidNames.length}):`)
+  for (const name of solidNames) {
+    console.log(`    - ${name}`)
+  }
+
+  // Board solid + at least 2 separate component solids
+  expect(solidNames.length).toBeGreaterThanOrEqual(3)
+
+  // Each component should have its own named solid (not a single merged "Components")
+  expect(solidNames.some((n) => n === "Components")).toBe(false)
+
+  // Validate STEP file with occt-import-js
+  const occtResult = await importStepWithOcct(stepText)
+  expect(occtResult.success).toBe(true)
+  // Should have multiple meshes (one per solid)
+  expect(occtResult.meshes.length).toBeGreaterThanOrEqual(3)
+
+  console.log(`  occt meshes: ${occtResult.meshes.length}`)
+
+  // Write debug output
+  await Bun.write("debug-output/separate-solids.step", stepText)
+
+  await expect(stepText).toMatchStepSnapshot(
+    import.meta.path,
+    "separate-solids",
+  )
+}, 30000)