Improve roof node editing

packages/core/src/registry/handles.ts

@@ -316,7 +316,9 @@ export type TapActionHandle<N = any> = {
  * the hit into the node's parent-local frame, and reports the new local XZ
  * (optionally grid-snapped via `snapExtents`) to `apply`. Press-drag-release
  * with the same live-override → commit-on-release flow as the resize / rotate
- * handles. Rendered as a 4-way cross of double-headed arrows.
+ * handles. Rendered as a 4-way cross of double-headed arrows. Pure translation
+ * does not require geometry dirtying; renderers consume the live position
+ * override directly.
  */
 export type TranslateHandle<N = any> = {
   kind: 'translate'

packages/core/src/schema/index.ts

@@ -101,6 +101,7 @@ export {
   getActiveRoofHeight,
   getEffectiveSegmentSurfaceMaterial,
   getPitchFromActiveRoofHeight,
+  getRoofSegmentSurfaceY,
   getSegmentSlopeFrame,
   hasSegmentMaterialOverride,
   ROOF_SHAPE_DEFAULTS,

packages/core/src/schema/nodes/roof-segment.ts

@@ -181,7 +181,6 @@ function getPrimarySlopeRun(input: PitchInputs & ShapeRatios): number {
       return min * input.mansardSteepWidthRatio
     case 'dutch':
       return min * input.dutchHipWidthRatio
-    case 'hip':
     default:
       return min / 2
   }
@@ -253,6 +252,42 @@ export function getActiveRoofHeight(node: Parameters<typeof getSegmentSlopeFrame
   return getSegmentSlopeFrame(node).activeRh
 }
 
+/** Segment-local surface height used by roof accessory placement and hit disambiguation. */
+export function getRoofSegmentSurfaceY(
+  node: Pick<RoofSegmentNode, 'roofType' | 'width' | 'depth' | 'wallHeight'> &
+    Parameters<typeof getSegmentSlopeFrame>[0],
+  localX: number,
+  localZ: number,
+): number {
+  const activeRh = getActiveRoofHeight(node)
+  const peakY = node.wallHeight + activeRh
+  if (activeRh === 0) return node.wallHeight
+
+  if (
+    node.roofType === 'gable' ||
+    node.roofType === 'gambrel' ||
+    node.roofType === 'mansard' ||
+    node.roofType === 'dutch'
+  ) {
+    const t = node.depth > 0 ? Math.abs(localZ) / (node.depth / 2) : 0
+    return peakY - t * activeRh
+  }
+
+  if (node.roofType === 'shed') {
+    const t = (localZ + node.depth / 2) / (node.depth || 1)
+    return peakY - t * activeRh
+  }
+
+  if (node.roofType === 'hip') {
+    const fx = node.width > 0 ? Math.abs(localX) / (node.width / 2) : 0
+    const fz = node.depth > 0 ? Math.abs(localZ) / (node.depth / 2) : 0
+    return peakY - Math.max(fx, fz) * activeRh
+  }
+
+  const t = node.depth > 0 ? Math.abs(localZ) / (node.depth / 2) : 0
+  return peakY - t * activeRh
+}
+
 /**
  * Inverse of `getActiveRoofHeight` — recover the pitch a legacy
  * `roofHeight` value would correspond to. Used by the scene migration.