Add click-targeted stair materials and UV mapping

packages/core/src/schema/index.ts

@@ -50,12 +50,14 @@ export { ScanNode } from './nodes/scan'
 export { SiteNode } from './nodes/site'
 export { SlabNode } from './nodes/slab'
 export {
+  getEffectiveStairSurfaceMaterial,
   StairNode,
   StairRailingMode,
   StairSlabOpeningMode,
   StairTopLandingMode,
   StairType,
 } from './nodes/stair'
+export type { StairSurfaceMaterialRole, StairSurfaceMaterialSpec } from './nodes/stair'
 export { AttachmentSide, StairSegmentNode, StairSegmentType } from './nodes/stair-segment'
 export { SurfaceHoleMetadata } from './nodes/surface-hole-metadata'
 export type { WallSurfaceMaterialSpec, WallSurfaceSide } from './nodes/wall'

packages/core/src/schema/nodes/stair.ts

@@ -1,7 +1,7 @@
 import dedent from 'dedent'
 import { z } from 'zod'
 import { BaseNode, nodeType, objectId } from '../base'
-import { MaterialSchema } from '../material'
+import { type MaterialSchema, MaterialSchema as MaterialSchemaSchema } from '../material'
 import { StairSegmentNode } from './stair-segment'
 
 export const StairRailingMode = z.enum(['none', 'left', 'right', 'both'])
@@ -13,12 +13,23 @@ export type StairRailingMode = z.infer<typeof StairRailingMode>
 export type StairType = z.infer<typeof StairType>
 export type StairTopLandingMode = z.infer<typeof StairTopLandingMode>
 export type StairSlabOpeningMode = z.infer<typeof StairSlabOpeningMode>
+export type StairSurfaceMaterialRole = 'railing' | 'tread' | 'side'
+export type StairSurfaceMaterialSpec = {
+  material?: MaterialSchema
+  materialPreset?: string
+}
 
 export const StairNode = BaseNode.extend({
   id: objectId('stair'),
   type: nodeType('stair'),
-  material: MaterialSchema.optional(),
+  material: MaterialSchemaSchema.optional(),
   materialPreset: z.string().optional(),
+  railingMaterial: MaterialSchemaSchema.optional(),
+  railingMaterialPreset: z.string().optional(),
+  treadMaterial: MaterialSchemaSchema.optional(),
+  treadMaterialPreset: z.string().optional(),
+  sideMaterial: MaterialSchemaSchema.optional(),
+  sideMaterialPreset: z.string().optional(),
   position: z.tuple([z.number(), z.number(), z.number()]).default([0, 0, 0]),
   // Rotation around Y axis in radians
   rotation: z.number().default(0),
@@ -71,3 +82,74 @@ export const StairNode = BaseNode.extend({
 )
 
 export type StairNode = z.infer<typeof StairNode>
+
+function getLegacyStairSurfaceMaterial(node: StairNode): StairSurfaceMaterialSpec {
+  return {
+    material: node.material,
+    materialPreset: node.materialPreset,
+  }
+}
+
+export function getEffectiveStairSurfaceMaterial(
+  node: StairNode,
+  role: StairSurfaceMaterialRole,
+): StairSurfaceMaterialSpec {
+  if (role === 'railing') {
+    if (node.railingMaterial !== undefined || typeof node.railingMaterialPreset === 'string') {
+      return {
+        material: node.railingMaterial,
+        materialPreset:
+          typeof node.railingMaterialPreset === 'string' ? node.railingMaterialPreset : undefined,
+      }
+    }
+  }
+
+  if (role === 'tread') {
+    if (node.treadMaterial !== undefined || typeof node.treadMaterialPreset === 'string') {
+      return {
+        material: node.treadMaterial,
+        materialPreset:
+          typeof node.treadMaterialPreset === 'string' ? node.treadMaterialPreset : undefined,
+      }
+    }
+  }
+
+  if (role === 'side') {
+    if (node.sideMaterial !== undefined || typeof node.sideMaterialPreset === 'string') {
+      return {
+        material: node.sideMaterial,
+        materialPreset:
+          typeof node.sideMaterialPreset === 'string' ? node.sideMaterialPreset : undefined,
+      }
+    }
+  }
+
+  const treadFallback = {
+    material: node.treadMaterial,
+    materialPreset: typeof node.treadMaterialPreset === 'string' ? node.treadMaterialPreset : undefined,
+  }
+  const sideFallback = {
+    material: node.sideMaterial,
+    materialPreset: typeof node.sideMaterialPreset === 'string' ? node.sideMaterialPreset : undefined,
+  }
+
+  if (role === 'tread' && (sideFallback.material !== undefined || sideFallback.materialPreset !== undefined)) {
+    return sideFallback
+  }
+
+  if (role === 'side' && (treadFallback.material !== undefined || treadFallback.materialPreset !== undefined)) {
+    return treadFallback
+  }
+
+  if (role === 'railing') {
+    if (treadFallback.material !== undefined || treadFallback.materialPreset !== undefined) {
+      return treadFallback
+    }
+
+    if (sideFallback.material !== undefined || sideFallback.materialPreset !== undefined) {
+      return sideFallback
+    }
+  }
+
+  return getLegacyStairSurfaceMaterial(node)
+}

packages/core/src/store/use-scene.ts

@@ -143,6 +143,87 @@ function migrateWallSurfaceMaterials(node: Record<string, any>) {
   return node
 }
 
+function migrateStairSurfaceMaterials(node: Record<string, any>) {
+  const hasRailing =
+    node.railingMaterial !== undefined || typeof node.railingMaterialPreset === 'string'
+  const hasTread = node.treadMaterial !== undefined || typeof node.treadMaterialPreset === 'string'
+  const hasSide = node.sideMaterial !== undefined || typeof node.sideMaterialPreset === 'string'
+  const legacyFinish = {
+    material: node.material,
+    materialPreset: typeof node.materialPreset === 'string' ? node.materialPreset : undefined,
+  }
+
+  const resolveBodyFallback = () => {
+    if (node.treadMaterial !== undefined || typeof node.treadMaterialPreset === 'string') {
+      return {
+        material: node.treadMaterial,
+        materialPreset: typeof node.treadMaterialPreset === 'string' ? node.treadMaterialPreset : undefined,
+      }
+    }
+
+    if (node.sideMaterial !== undefined || typeof node.sideMaterialPreset === 'string') {
+      return {
+        material: node.sideMaterial,
+        materialPreset: typeof node.sideMaterialPreset === 'string' ? node.sideMaterialPreset : undefined,
+      }
+    }
+
+    return legacyFinish
+  }
+
+  if (!hasRailing && !hasTread && !hasSide) {
+    if (legacyFinish.material === undefined && legacyFinish.materialPreset === undefined) {
+      return node
+    }
+
+    return {
+      ...node,
+      railingMaterial: legacyFinish.material,
+      railingMaterialPreset: legacyFinish.materialPreset,
+      treadMaterial: legacyFinish.material,
+      treadMaterialPreset: legacyFinish.materialPreset,
+      sideMaterial: legacyFinish.material,
+      sideMaterialPreset: legacyFinish.materialPreset,
+    }
+  }
+
+  const next = { ...node }
+
+  if (!hasTread) {
+    const fallback =
+      node.sideMaterial !== undefined || typeof node.sideMaterialPreset === 'string'
+        ? {
+            material: node.sideMaterial,
+            materialPreset:
+              typeof node.sideMaterialPreset === 'string' ? node.sideMaterialPreset : undefined,
+          }
+        : resolveBodyFallback()
+    next.treadMaterial = fallback.material
+    next.treadMaterialPreset = fallback.materialPreset
+  }
+
+  if (!hasSide) {
+    const fallback =
+      node.treadMaterial !== undefined || typeof node.treadMaterialPreset === 'string'
+        ? {
+            material: node.treadMaterial,
+            materialPreset:
+              typeof node.treadMaterialPreset === 'string' ? node.treadMaterialPreset : undefined,
+          }
+        : resolveBodyFallback()
+    next.sideMaterial = fallback.material
+    next.sideMaterialPreset = fallback.materialPreset
+  }
+
+  if (!hasRailing) {
+    const fallback = resolveBodyFallback()
+    next.railingMaterial = fallback.material
+    next.railingMaterialPreset = fallback.materialPreset
+  }
+
+  return next
+}
+
 function migrateNodes(nodes: Record<string, any>): Record<string, AnyNode> {
   const patchedNodes = { ...nodes }
   for (const [id, node] of Object.entries(patchedNodes)) {
@@ -184,7 +265,7 @@ function migrateNodes(nodes: Record<string, any>): Record<string, AnyNode> {
     }
 
     if (node.type === 'stair') {
-      const normalized = normalizeStairNode(node)
+      const normalized = normalizeStairNode(migrateStairSurfaceMaterials(node))
       if (normalized) {
         patchedNodes[id] = normalized
       }

packages/core/src/systems/stair/stair-system.tsx

@@ -12,6 +12,10 @@ import { syncAutoStairOpenings } from './stair-opening-sync'
 const pendingStairUpdates = new Set<AnyNodeId>()
 const MAX_STAIRS_PER_FRAME = 2
 const MAX_SEGMENTS_PER_FRAME = 4
+const STAIR_TREAD_MATERIAL_INDEX = 0
+const STAIR_SIDE_MATERIAL_INDEX = 1
+const _uvPosition = new THREE.Vector3()
+const _uvNormal = new THREE.Vector3()
 
 // ============================================================================
 // STAIR SYSTEM
@@ -198,7 +202,7 @@ function generateStairSegmentGeometry(
 
   shape.lineTo(0, 0)
 
-  const geometry = new THREE.ExtrudeGeometry(shape, {
+  const extrudedGeometry = new THREE.ExtrudeGeometry(shape, {
     steps: 1,
     depth: width,
     bevelEnabled: false,
@@ -209,7 +213,16 @@ function generateStairSegmentGeometry(
   const matrix = new THREE.Matrix4()
   matrix.makeRotationY(-Math.PI / 2)
   matrix.setPosition(width / 2, 0, 0)
-  geometry.applyMatrix4(matrix)
+  extrudedGeometry.applyMatrix4(matrix)
+  extrudedGeometry.computeVertexNormals()
+
+  const geometry = extrudedGeometry.toNonIndexed() ?? extrudedGeometry
+  if (geometry !== extrudedGeometry) {
+    extrudedGeometry.dispose()
+  }
+
+  applyStairSegmentUvs(geometry)
+  ensureUv2Attribute(geometry)
 
   return geometry
 }
@@ -219,6 +232,7 @@ function updateStairSegmentGeometry(node: StairSegmentNode, mesh: THREE.Mesh) {
   const absoluteHeight = computeAbsoluteHeight(node)
 
   const newGeometry = generateStairSegmentGeometry(node, absoluteHeight)
+  applyStraightStairMaterialGroups(newGeometry)
 
   mesh.geometry.dispose()
   mesh.geometry = newGeometry
@@ -363,6 +377,7 @@ function updateMergedStairGeometry(
   }
 
   const merged = mergeGeometries(geometries, false) ?? createEmptyGeometry()
+  applyStraightStairMaterialGroups(merged)
   replaceMeshGeometry(mergedMesh, merged)
 
   // Dispose individual geometries
@@ -371,6 +386,108 @@ function updateMergedStairGeometry(
   }
 }
 
+function applyStraightStairMaterialGroups(geometry: THREE.BufferGeometry) {
+  const position = geometry.getAttribute('position')
+  if (!position || position.count < 3) {
+    geometry.clearGroups()
+    return
+  }
+
+  const index = geometry.getIndex()
+  const triangleCount = index ? index.count / 3 : position.count / 3
+
+  if (!Number.isFinite(triangleCount) || triangleCount <= 0) {
+    geometry.clearGroups()
+    return
+  }
+
+  const triangleMaterials: number[] = new Array(triangleCount)
+  const v0 = new THREE.Vector3()
+  const v1 = new THREE.Vector3()
+  const v2 = new THREE.Vector3()
+  const edge1 = new THREE.Vector3()
+  const edge2 = new THREE.Vector3()
+  const normal = new THREE.Vector3()
+
+  for (let triangleIndex = 0; triangleIndex < triangleCount; triangleIndex++) {
+    const vertexOffset = triangleIndex * 3
+    const a = index ? index.getX(vertexOffset) : vertexOffset
+    const b = index ? index.getX(vertexOffset + 1) : vertexOffset + 1
+    const c = index ? index.getX(vertexOffset + 2) : vertexOffset + 2
+
+    v0.fromBufferAttribute(position, a)
+    v1.fromBufferAttribute(position, b)
+    v2.fromBufferAttribute(position, c)
+
+    edge1.subVectors(v1, v0)
+    edge2.subVectors(v2, v0)
+    normal.crossVectors(edge1, edge2)
+
+    triangleMaterials[triangleIndex] =
+      normal.lengthSq() > 0 && normal.normalize().y > 0.75
+        ? STAIR_TREAD_MATERIAL_INDEX
+        : STAIR_SIDE_MATERIAL_INDEX
+  }
+
+  geometry.clearGroups()
+
+  let currentMaterial = triangleMaterials[0]
+  let groupStart = 0
+
+  for (let triangleIndex = 1; triangleIndex < triangleMaterials.length; triangleIndex++) {
+    const materialIndex = triangleMaterials[triangleIndex]
+    if (materialIndex === currentMaterial) continue
+
+    geometry.addGroup(groupStart * 3, (triangleIndex - groupStart) * 3, currentMaterial)
+    groupStart = triangleIndex
+    currentMaterial = materialIndex
+  }
+
+  geometry.addGroup(
+    groupStart * 3,
+    (triangleMaterials.length - groupStart) * 3,
+    currentMaterial ?? STAIR_SIDE_MATERIAL_INDEX,
+  )
+}
+
+function applyStairSegmentUvs(geometry: THREE.BufferGeometry) {
+  const position = geometry.getAttribute('position')
+  const normal = geometry.getAttribute('normal')
+
+  if (!position || !normal || position.count === 0) {
+    geometry.deleteAttribute('uv')
+    return
+  }
+
+  const uv: number[] = []
+
+  for (let index = 0; index < position.count; index++) {
+    _uvPosition.fromBufferAttribute(position, index)
+    _uvNormal.fromBufferAttribute(normal, index).normalize()
+
+    const absX = Math.abs(_uvNormal.x)
+    const absY = Math.abs(_uvNormal.y)
+    const absZ = Math.abs(_uvNormal.z)
+
+    if (absY >= absX && absY >= absZ) {
+      uv.push(_uvPosition.x, _uvPosition.z)
+    } else if (absX >= absZ) {
+      uv.push(_uvPosition.z, _uvPosition.y)
+    } else {
+      uv.push(_uvPosition.x, _uvPosition.y)
+    }
+  }
+
+  geometry.setAttribute('uv', new THREE.Float32BufferAttribute(uv, 2))
+}
+
+function ensureUv2Attribute(geometry: THREE.BufferGeometry) {
+  const uv = geometry.getAttribute('uv')
+  if (!uv) return
+
+  geometry.setAttribute('uv2', new THREE.Float32BufferAttribute(Array.from(uv.array), 2))
+}
+
 // ============================================================================
 // SEGMENT CHAINING
 // ============================================================================
@@ -441,6 +558,8 @@ function rotateXZ(x: number, z: number, angle: number): [number, number] {
 function createEmptyGeometry(): THREE.BufferGeometry {
   const geometry = new THREE.BufferGeometry()
   geometry.setAttribute('position', new THREE.Float32BufferAttribute([], 3))
+  geometry.addGroup(0, 0, STAIR_TREAD_MATERIAL_INDEX)
+  geometry.addGroup(0, 0, STAIR_SIDE_MATERIAL_INDEX)
   return geometry
 }
 

packages/editor/src/components/editor/selection-manager.tsx

@@ -7,6 +7,9 @@ import {
   type NodeEvent,
   resolveLevelId,
   sceneRegistry,
+  type StairEvent,
+  type StairNode,
+  type StairSegmentEvent,
   useScene,
   type WallEvent,
   type WallSurfaceSide,
@@ -16,7 +19,7 @@ import { useViewer } from '@pascal-app/viewer'
 import { useCallback, useEffect, useRef } from 'react'
 import { Color, type Material, type Mesh, type Object3D } from 'three'
 import { sfxEmitter } from '../../lib/sfx-bus'
-import useEditor, { type Phase, type StructureLayer } from './../../store/use-editor'
+import useEditor, { type Phase, type StairMaterialTargetRole, type StructureLayer } from './../../store/use-editor'
 import { boxSelectHandled } from '../tools/select/box-select-tool'
 
 const isNodeInCurrentLevel = (node: AnyNode): boolean => {
@@ -96,6 +99,35 @@ function resolveWallMaterialTarget(event: WallEvent): WallSurfaceSide | null {
   return hitFace === 'front' ? 'interior' : 'exterior'
 }
 
+function resolveStairMaterialTarget(
+  event: StairEvent | StairSegmentEvent,
+): StairMaterialTargetRole | null {
+  const hitObjectName = event.nativeEvent.object?.name ?? ''
+
+  if (hitObjectName.startsWith('stair-railing')) {
+    return 'railing'
+  }
+
+  if (event.materialIndex === 0) {
+    return 'tread'
+  }
+
+  if (event.materialIndex === 1) {
+    return 'side'
+  }
+
+  const normalY = event.normal?.[1]
+  if (normalY !== undefined && normalY > 0.75) {
+    return 'tread'
+  }
+
+  if (normalY !== undefined && Math.abs(normalY) <= 0.75) {
+    return 'side'
+  }
+
+  return null
+}
+
 const HIGHLIGHT_PROFILES = {
   delete: {
     color: new Color('#dc2626'),
@@ -484,6 +516,28 @@ export const SelectionManager = () => {
           useEditor.getState().setSelectedWallMaterialTarget(null)
         }
 
+        if (
+          (node.type === 'stair' || node.type === 'stair-segment') &&
+          nodeToSelect.type === 'stair'
+        ) {
+          const nextStairMaterialTarget = resolveStairMaterialTarget(
+            event as StairEvent | StairSegmentEvent,
+          )
+          if (nextStairMaterialTarget) {
+            useEditor.getState().setSelectedStairMaterialTarget({
+              stairId: nodeToSelect.id,
+              role: nextStairMaterialTarget,
+            })
+          } else {
+            const currentStairMaterialTarget = useEditor.getState().selectedStairMaterialTarget
+            if (currentStairMaterialTarget?.stairId !== nodeToSelect.id) {
+              useEditor.getState().setSelectedStairMaterialTarget(null)
+            }
+          }
+        } else if (useEditor.getState().selectedStairMaterialTarget) {
+          useEditor.getState().setSelectedStairMaterialTarget(null)
+        }
+
         // Reset the handled flag after a short delay to allow grid:click to be ignored
         setTimeout(() => {
           clickHandledRef.current = false
@@ -517,6 +571,7 @@ export const SelectionManager = () => {
       const activeStrategy = SELECTION_STRATEGIES[phase]
       if (activeStrategy) activeStrategy.handleDeselect()
       useEditor.getState().setSelectedWallMaterialTarget(null)
+      useEditor.getState().setSelectedStairMaterialTarget(null)
 
       // When deselecting from zone mode, return to structure select
       if (phase === 'structure' && structureLayer === 'zones') {
@@ -752,6 +807,8 @@ export const SelectionManager = () => {
 const SelectionStateSync = () => {
   const selectedWallMaterialTarget = useEditor((s) => s.selectedWallMaterialTarget)
   const setSelectedWallMaterialTarget = useEditor((s) => s.setSelectedWallMaterialTarget)
+  const selectedStairMaterialTarget = useEditor((s) => s.selectedStairMaterialTarget)
+  const setSelectedStairMaterialTarget = useEditor((s) => s.setSelectedStairMaterialTarget)
   const singleSelectedId = useViewer((s) =>
     s.selection.selectedIds.length === 1 ? s.selection.selectedIds[0] : null,
   )
@@ -803,6 +860,25 @@ const SelectionStateSync = () => {
     }
   }, [selectedWallMaterialTarget, setSelectedWallMaterialTarget, singleSelectedId])
 
+  useEffect(() => {
+    if (!selectedStairMaterialTarget) return
+
+    if (!singleSelectedId) {
+      setSelectedStairMaterialTarget(null)
+      return
+    }
+
+    const selectedNode = useScene.getState().nodes[singleSelectedId as AnyNodeId]
+    if (!(selectedNode?.type === 'stair')) {
+      setSelectedStairMaterialTarget(null)
+      return
+    }
+
+    if (selectedStairMaterialTarget.stairId !== selectedNode.id) {
+      setSelectedStairMaterialTarget(null)
+    }
+  }, [selectedStairMaterialTarget, setSelectedStairMaterialTarget, singleSelectedId])
+
   return null
 }
 

packages/editor/src/components/ui/panels/stair-panel.tsx

@@ -3,10 +3,12 @@
 import {
   type AnyNode,
   type AnyNodeId,
+  getEffectiveStairSurfaceMaterial,
   type LevelNode,
   type MaterialSchema,
   type StairNode,
   type StairRailingMode,
+  type StairSurfaceMaterialRole,
   type StairSlabOpeningMode,
   type StairTopLandingMode,
   type StairType,
@@ -31,6 +33,32 @@ import { SliderControl } from '../controls/slider-control'
 import { ToggleControl } from '../controls/toggle-control'
 import { PanelWrapper } from './panel-wrapper'
 
+function buildStairSurfaceMaterialPatch(
+  node: StairNode,
+  targetRole: StairSurfaceMaterialRole,
+  material: MaterialSchema | undefined,
+  materialPreset: string | undefined,
+): Partial<StairNode> {
+  const nextSurfaceMaterial = { material, materialPreset }
+  const nextRailing =
+    targetRole === 'railing' ? nextSurfaceMaterial : getEffectiveStairSurfaceMaterial(node, 'railing')
+  const nextTread =
+    targetRole === 'tread' ? nextSurfaceMaterial : getEffectiveStairSurfaceMaterial(node, 'tread')
+  const nextSide =
+    targetRole === 'side' ? nextSurfaceMaterial : getEffectiveStairSurfaceMaterial(node, 'side')
+
+  return {
+    railingMaterial: nextRailing.material,
+    railingMaterialPreset: nextRailing.materialPreset,
+    treadMaterial: nextTread.material,
+    treadMaterialPreset: nextTread.materialPreset,
+    sideMaterial: nextSide.material,
+    sideMaterialPreset: nextSide.materialPreset,
+    material: undefined,
+    materialPreset: undefined,
+  }
+}
+
 const RAILING_MODE_OPTIONS: { label: string; value: StairRailingMode }[] = [
   { label: 'None', value: 'none' },
   { label: 'Left', value: 'left' },
@@ -62,6 +90,7 @@ export function StairPanel() {
   const createNode = useScene((s) => s.createNode)
   const createNodes = useScene((s) => s.createNodes)
   const setMovingNode = useEditor((s) => s.setMovingNode)
+  const selectedStairMaterialTarget = useEditor((s) => s.selectedStairMaterialTarget)
 
   const node = useScene((s) =>
     selectedId ? (s.nodes[selectedId as AnyNode['id']] as StairNode | undefined) : undefined,
@@ -92,18 +121,27 @@ export function StairPanel() {
     [selectedId, updateNode],
   )
 
-  const handleMaterialChange = useCallback(
+  const materialTargetRole =
+    selectedStairMaterialTarget && selectedStairMaterialTarget.stairId === node?.id
+      ? selectedStairMaterialTarget.role
+      : null
+  const materialPickerValue =
+    node && materialTargetRole ? getEffectiveStairSurfaceMaterial(node, materialTargetRole) : {}
+
+  const handleTargetedMaterialChange = useCallback(
     (material: MaterialSchema) => {
-      handleUpdate({ material, materialPreset: undefined })
+      if (!node || !materialTargetRole) return
+      handleUpdate(buildStairSurfaceMaterialPatch(node, materialTargetRole, material, undefined))
     },
-    [handleUpdate],
+    [handleUpdate, materialTargetRole, node],
   )
 
-  const handleMaterialPresetChange = useCallback(
+  const handleTargetedMaterialPresetChange = useCallback(
     (materialPreset: string) => {
-      handleUpdate({ materialPreset, material: undefined })
+      if (!node || !materialTargetRole) return
+      handleUpdate(buildStairSurfaceMaterialPatch(node, materialTargetRole, undefined, materialPreset))
     },
-    [handleUpdate],
+    [handleUpdate, materialTargetRole, node],
   )
 
   const handleClose = useCallback(() => {
@@ -569,13 +607,21 @@ export function StairPanel() {
         </ActionGroup>
       </PanelSection>
       <PanelSection title="Material">
-        <MaterialPicker
+        {!materialTargetRole ? (
-          nodeType="stair"
+          <div className="mb-3 rounded-lg border border-border/50 bg-[#2C2C2E] px-3 py-2 text-[11px] text-muted-foreground">
-          onChange={handleMaterialChange}
+            Click the stair surface you want to edit. Materials apply to one target at a time.
-          onSelectMaterialPreset={handleMaterialPresetChange}
+          </div>
-          selectedMaterialPreset={node.materialPreset}
+        ) : null}
-          value={node.material}
+        {materialTargetRole ? (
-        />
+          <MaterialPicker
+            hideSideControl
+            nodeType="stair"
+            onChange={handleTargetedMaterialChange}
+            onSelectMaterialPreset={handleTargetedMaterialPresetChange}
+            selectedMaterialPreset={materialPickerValue.materialPreset}
+            value={materialPickerValue.material}
+          />
+        ) : null}
       </PanelSection>
     </PanelWrapper>
   )

packages/editor/src/store/use-editor.tsx

@@ -86,6 +86,13 @@ export type SelectedWallMaterialTarget = {
   side: WallSurfaceSide
 }
 
+export type StairMaterialTargetRole = 'railing' | 'tread' | 'side'
+
+export type SelectedStairMaterialTarget = {
+  stairId: StairNode['id']
+  role: StairMaterialTargetRole
+}
+
 type EditorState = {
   phase: Phase
   setPhase: (phase: Phase) => void
@@ -135,6 +142,8 @@ type EditorState = {
   setCurvingWall: (wall: WallNode | null) => void
   selectedWallMaterialTarget: SelectedWallMaterialTarget | null
   setSelectedWallMaterialTarget: (target: SelectedWallMaterialTarget | null) => void
+  selectedStairMaterialTarget: SelectedStairMaterialTarget | null
+  setSelectedStairMaterialTarget: (target: SelectedStairMaterialTarget | null) => void
   selectedReferenceId: string | null
   setSelectedReferenceId: (id: string | null) => void
   // Space detection for cutaway mode
@@ -512,6 +521,8 @@ const useEditor = create<EditorState>()(
       setCurvingWall: (wall) => set({ curvingWall: wall }),
       selectedWallMaterialTarget: null,
       setSelectedWallMaterialTarget: (target) => set({ selectedWallMaterialTarget: target }),
+      selectedStairMaterialTarget: null,
+      setSelectedStairMaterialTarget: (target) => set({ selectedStairMaterialTarget: target }),
       selectedReferenceId: null,
       setSelectedReferenceId: (id) => set({ selectedReferenceId: id }),
       spaces: {},

packages/viewer/src/components/renderers/stair-segment/stair-segment-renderer.tsx

@@ -1,8 +1,8 @@
 import { type AnyNodeId, type StairNode, type StairSegmentNode, useRegistry, useScene } from '@pascal-app/core'
-import { useLayoutEffect, useMemo, useRef } from 'react'
+import { useEffect, useLayoutEffect, useMemo, useRef } from 'react'
-import type * as THREE from 'three'
+import * as THREE from 'three'
 import { useNodeEvents } from '../../../hooks/use-node-events'
-import { createMaterial, createMaterialFromPresetRef, DEFAULT_STAIR_MATERIAL } from '../../../lib/materials'
+import { getStraightStairSegmentBodyMaterials } from '../../../systems/stair/stair-materials'
 
 export const StairSegmentRenderer = ({ node }: { node: StairSegmentNode }) => {
   const ref = useRef<THREE.Mesh>(null!)
@@ -19,14 +19,7 @@ export const StairSegmentRenderer = ({ node }: { node: StairSegmentNode }) => {
     node.parentId ? (nodes[node.parentId as AnyNodeId] as StairNode | undefined) : undefined
 
   const material = useMemo(() => {
-    const effectiveMaterialPreset = node.materialPreset ?? parentNode?.materialPreset
+    return getStraightStairSegmentBodyMaterials(node, parentNode)
-    const effectiveMaterial = node.material ?? parentNode?.material
-
-    const presetMaterial = createMaterialFromPresetRef(effectiveMaterialPreset)
-    if (presetMaterial) return presetMaterial
-    const mat = effectiveMaterial
-    if (!mat) return DEFAULT_STAIR_MATERIAL
-    return createMaterial(mat)
   }, [
     node.materialPreset,
     node.material,
@@ -38,19 +31,37 @@ export const StairSegmentRenderer = ({ node }: { node: StairSegmentNode }) => {
     parentNode?.material?.preset,
     parentNode?.material?.properties,
     parentNode?.material?.texture,
+    parentNode?.railingMaterialPreset,
+    parentNode?.railingMaterial,
+    parentNode?.sideMaterialPreset,
+    parentNode?.sideMaterial,
+    parentNode?.treadMaterialPreset,
+    parentNode?.treadMaterial,
   ])
 
+  const placeholderGeometry = useMemo(() => {
+    const geometry = new THREE.BufferGeometry()
+    geometry.setAttribute('position', new THREE.Float32BufferAttribute([], 3))
+    geometry.addGroup(0, 0, 0)
+    geometry.addGroup(0, 0, 1)
+    return geometry
+  }, [])
+
+  useEffect(() => {
+    return () => {
+      placeholderGeometry.dispose()
+    }
+  }, [placeholderGeometry])
+
   return (
     <mesh
+      geometry={placeholderGeometry}
       material={material}
       position={node.position}
       ref={ref}
       rotation-y={node.rotation}
       visible={node.visible}
       {...handlers}
-    >
+    />
-      {/* StairSystem will replace this geometry in the next frame */}
-      <boxGeometry args={[0, 0, 0]} />
-    </mesh>
   )
 }

packages/viewer/src/components/renderers/stair/stair-renderer.tsx

@@ -5,14 +5,15 @@ import {
   useRegistry,
   useScene,
 } from '@pascal-app/core'
-import { useLayoutEffect, useMemo, useRef } from 'react'
+import { useEffect, useLayoutEffect, useMemo, useRef } from 'react'
 import * as THREE from 'three'
 import { useNodeEvents } from '../../../hooks/use-node-events'
+import { createMaterial, createMaterialFromPresetRef, DEFAULT_STAIR_MATERIAL } from '../../../lib/materials'
 import {
-  createMaterial,
+  getStairRailingMaterial,
-  createMaterialFromPresetRef,
+  getStairBodyMaterials,
-  DEFAULT_STAIR_MATERIAL,
+  type StairBodyMaterials,
-} from '../../../lib/materials'
+} from '../../../systems/stair/stair-materials'
 import { NodeRenderer } from '../node-renderer'
 
 type SegmentTransform = {
@@ -71,6 +72,48 @@ export const StairRenderer = ({ node }: { node: StairNode }) => {
     node.material?.texture,
   ])
 
+  const straightBodyMaterials = useMemo(
+    () => getStairBodyMaterials(node),
+    [
+      node.material,
+      node.materialPreset,
+      node.railingMaterial,
+      node.railingMaterialPreset,
+      node.sideMaterial,
+      node.sideMaterialPreset,
+      node.treadMaterial,
+      node.treadMaterialPreset,
+    ],
+  )
+
+  const railingMaterial = useMemo(
+    () => getStairRailingMaterial(node),
+    [
+      node.material,
+      node.materialPreset,
+      node.railingMaterial,
+      node.railingMaterialPreset,
+      node.sideMaterial,
+      node.sideMaterialPreset,
+      node.treadMaterial,
+      node.treadMaterialPreset,
+    ],
+  )
+
+  const straightPlaceholderGeometry = useMemo(() => {
+    const geometry = new THREE.BufferGeometry()
+    geometry.setAttribute('position', new THREE.Float32BufferAttribute([], 3))
+    geometry.addGroup(0, 0, 0)
+    geometry.addGroup(0, 0, 1)
+    return geometry
+  }, [])
+
+  useEffect(() => {
+    return () => {
+      straightPlaceholderGeometry.dispose()
+    }
+  }, [straightPlaceholderGeometry])
+
   return (
     <group
       position-x={node.position[0]}
@@ -81,12 +124,16 @@ export const StairRenderer = ({ node }: { node: StairNode }) => {
       {...handlers}
     >
       {isSegmentBasedStair ? (
-        <mesh castShadow material={material} name="merged-stair" receiveShadow>
+        <mesh
-          <boxGeometry args={[0, 0, 0]} />
+          castShadow
-        </mesh>
+          geometry={straightPlaceholderGeometry}
+          material={straightBodyMaterials}
+          name="merged-stair"
+          receiveShadow
+        />
       ) : null}
-      {!isSegmentBasedStair ? <CurvedStairBody material={material} stair={node} /> : null}
+      {!isSegmentBasedStair ? <CurvedStairBody bodyMaterials={straightBodyMaterials} stair={node} /> : null}
-      <StairRailings material={material} stair={node} />
+      <StairRailings material={railingMaterial} stair={node} />
       {isSegmentBasedStair ? (
         <group name="segments-wrapper" visible={false}>
           {(node.children ?? []).map((childId) => (
@@ -170,6 +217,7 @@ function StairRailings({ stair, material }: { stair: StairNode; material: THREE.
                   geometry={BALUSTER_GEOMETRY}
                   key={`${stair.id}-curved-baluster-${sideIndex}-${pointIndex}`}
                   material={material}
+                  name="stair-railing-baluster"
                   position={[point[0], point[1] + railHeight / 2, point[2]]}
                   receiveShadow
                   scale={[balusterRadius, railHeight, balusterRadius]}
@@ -227,6 +275,7 @@ function StairRailings({ stair, material }: { stair: StairNode; material: THREE.
                   geometry={BALUSTER_GEOMETRY}
                   key={`${segmentPath.layout.segment.id}-${sidePath.side}-baluster-${pointIndex}`}
                   material={material}
+                  name="stair-railing-baluster"
                   position={[point[2], point[1] + railHeight / 2, point[0]]}
                   receiveShadow
                   scale={[balusterRadius, railHeight, balusterRadius]}
@@ -333,6 +382,8 @@ function StairRailings({ stair, material }: { stair: StairNode; material: THREE.
 
 const BALUSTER_GEOMETRY = new THREE.CylinderGeometry(1, 1, 1, 8)
 const RAIL_GEOMETRY = new THREE.CylinderGeometry(1, 1, 1, 8)
+const STAIR_TREAD_MATERIAL_INDEX = 0
+const STAIR_SIDE_MATERIAL_INDEX = 1
 
 function RailSegment({
   start,
@@ -367,6 +418,7 @@ function RailSegment({
       castShadow
       geometry={RAIL_GEOMETRY}
       material={material}
+      name="stair-railing-rail"
       position={[midpoint.x, midpoint.y, midpoint.z]}
       quaternion={quaternion}
       receiveShadow
@@ -375,7 +427,14 @@ function RailSegment({
   )
 }
 
-function CurvedStairBody({ stair, material }: { stair: StairNode; material: THREE.Material }) {
+function CurvedStairBody({
+  stair,
+  bodyMaterials,
+}: {
+  stair: StairNode
+  bodyMaterials: StairBodyMaterials
+}) {
+  const sideMaterial = bodyMaterials[1]
   const stepCount = Math.max(2, Math.round(stair.stepCount ?? 10))
   const totalRise = Math.max(stair.totalRise ?? 2.5, 0.1)
   const stepHeight = totalRise / stepCount
@@ -411,7 +470,8 @@ function CurvedStairBody({ stair, material }: { stair: StairNode; material: THRE
         <mesh
           castShadow
           receiveShadow
-          material={material}
+          material={sideMaterial}
+          name="stair-side"
           position={[0, spiralColumnHeight / 2, 0]}
         >
           <cylinderGeometry
@@ -443,7 +503,8 @@ function CurvedStairBody({ stair, material }: { stair: StairNode; material: THRE
             {isSpiral && (stair.showStepSupports ?? true) ? (
               <mesh
                 castShadow
-                material={material}
+                material={sideMaterial}
+                name="stair-side"
                 position={[
                   Math.cos(midAngle) *
                     (spiralColumnRadius +
@@ -470,7 +531,7 @@ function CurvedStairBody({ stair, material }: { stair: StairNode; material: THRE
             <CurvedStepMesh
               endAngle={endAngle}
               innerRadius={innerRadius}
-              material={material}
+              material={bodyMaterials}
               outerRadius={outerRadius}
               positionY={0}
               startAngle={startAngle}
@@ -484,7 +545,7 @@ function CurvedStairBody({ stair, material }: { stair: StairNode; material: THRE
         <CurvedStepMesh
           endAngle={sweepAngle / 2 + spiralLandingSweep}
           innerRadius={innerRadius}
-          material={material}
+          material={bodyMaterials}
           outerRadius={outerRadius}
           positionY={spiralLastStepTop}
           startAngle={sweepAngle / 2}
@@ -513,7 +574,7 @@ function CurvedStepMesh({
   stepHeight: number
   thickness: number
   positionY: number
-  material: THREE.Material
+  material: THREE.Material | THREE.Material[]
 }) {
   const geometry = useMemo(
     () =>
@@ -556,15 +617,39 @@ function buildCurvedStepGeometry(
 
   const positions: number[] = []
   const normals: number[] = []
+  const uvs: number[] = []
+  const triangleMaterialIndices: number[] = []
 
   const pointOnArc = (radius: number, angle: number, y: number) =>
     new THREE.Vector3(Math.cos(angle) * radius, y, Math.sin(angle) * radius)
 
+  const pushUv = (point: THREE.Vector3, normal: THREE.Vector3, materialIndex: number) => {
+    if (materialIndex === STAIR_TREAD_MATERIAL_INDEX) {
+      const angle = Math.atan2(point.z, point.x)
+      const arcOffset = (angle - startAngle) * Math.max((innerRadius + outerRadius) * 0.5, 0.01)
+      uvs.push(arcOffset, Math.sqrt(point.x * point.x + point.z * point.z) - innerRadius)
+      return
+    }
+
+    const absX = Math.abs(normal.x)
+    const absY = Math.abs(normal.y)
+    const absZ = Math.abs(normal.z)
+
+    if (absY >= absX && absY >= absZ) {
+      uvs.push(point.x, point.z)
+    } else if (absX >= absZ) {
+      uvs.push(point.z, point.y)
+    } else {
+      uvs.push(point.x, point.y)
+    }
+  }
+
   const pushTriangle = (
     a: THREE.Vector3,
     b: THREE.Vector3,
     c: THREE.Vector3,
     normal: THREE.Vector3,
+    materialIndex: number,
   ) => {
     const edgeAB = b.clone().sub(a)
     const edgeAC = c.clone().sub(a)
@@ -573,7 +658,9 @@ function buildCurvedStepGeometry(
     for (const point of ordered) {
       positions.push(point.x, point.y, point.z)
       normals.push(normal.x, normal.y, normal.z)
+      pushUv(point, normal, materialIndex)
     }
+    triangleMaterialIndices.push(materialIndex)
   }
 
   const pushQuad = (
@@ -582,9 +669,10 @@ function buildCurvedStepGeometry(
     c: THREE.Vector3,
     d: THREE.Vector3,
     normal: THREE.Vector3,
+    materialIndex: number,
   ) => {
-    pushTriangle(a, b, c, normal)
+    pushTriangle(a, b, c, normal, materialIndex)
-    pushTriangle(a, c, d, normal)
+    pushTriangle(a, c, d, normal, materialIndex)
   }
 
   const upNormal = new THREE.Vector3(0, 1, 0)
@@ -609,10 +697,38 @@ function buildCurvedStepGeometry(
     const outerNormal = new THREE.Vector3(Math.cos(midAngle), 0, Math.sin(midAngle)).normalize()
     const innerNormal = new THREE.Vector3(-Math.cos(midAngle), 0, -Math.sin(midAngle)).normalize()
 
-    pushQuad(innerStartTop, outerStartTop, outerEndTop, innerEndTop, upNormal)
+    pushQuad(
-    pushQuad(innerStartBottom, innerEndBottom, outerEndBottom, outerStartBottom, downNormal)
+      innerStartTop,
-    pushQuad(innerStartBottom, innerStartTop, innerEndTop, innerEndBottom, innerNormal)
+      outerStartTop,
-    pushQuad(outerStartBottom, outerEndBottom, outerEndTop, outerStartTop, outerNormal)
+      outerEndTop,
+      innerEndTop,
+      upNormal,
+      STAIR_TREAD_MATERIAL_INDEX,
+    )
+    pushQuad(
+      innerStartBottom,
+      innerEndBottom,
+      outerEndBottom,
+      outerStartBottom,
+      downNormal,
+      STAIR_SIDE_MATERIAL_INDEX,
+    )
+    pushQuad(
+      innerStartBottom,
+      innerStartTop,
+      innerEndTop,
+      innerEndBottom,
+      innerNormal,
+      STAIR_SIDE_MATERIAL_INDEX,
+    )
+    pushQuad(
+      outerStartBottom,
+      outerEndBottom,
+      outerEndTop,
+      outerStartTop,
+      outerNormal,
+      STAIR_SIDE_MATERIAL_INDEX,
+    )
   }
 
   const startInnerBottom = pointOnArc(innerRadius, startAngle, y0)
@@ -634,12 +750,49 @@ function buildCurvedStepGeometry(
     sweepDirection * Math.cos(endAngle),
   ).normalize()
 
-  pushQuad(startInnerBottom, startOuterBottom, startOuterTop, startInnerTop, startNormal)
+  pushQuad(
-  pushQuad(endInnerBottom, endInnerTop, endOuterTop, endOuterBottom, endNormal)
+    startInnerBottom,
+    startOuterBottom,
+    startOuterTop,
+    startInnerTop,
+    startNormal,
+    STAIR_SIDE_MATERIAL_INDEX,
+  )
+  pushQuad(
+    endInnerBottom,
+    endInnerTop,
+    endOuterTop,
+    endOuterBottom,
+    endNormal,
+    STAIR_SIDE_MATERIAL_INDEX,
+  )
 
   const geometry = new THREE.BufferGeometry()
   geometry.setAttribute('position', new THREE.Float32BufferAttribute(positions, 3))
   geometry.setAttribute('normal', new THREE.Float32BufferAttribute(normals, 3))
+  geometry.setAttribute('uv', new THREE.Float32BufferAttribute(uvs, 2))
+  geometry.clearGroups()
+
+  let currentMaterial = triangleMaterialIndices[0]
+  let groupStart = 0
+
+  for (let triangleIndex = 1; triangleIndex < triangleMaterialIndices.length; triangleIndex++) {
+    const materialIndex = triangleMaterialIndices[triangleIndex]
+    if (materialIndex === currentMaterial) continue
+
+    geometry.addGroup(groupStart * 3, (triangleIndex - groupStart) * 3, currentMaterial)
+    groupStart = triangleIndex
+    currentMaterial = materialIndex
+  }
+
+  if (triangleMaterialIndices.length > 0) {
+    geometry.addGroup(
+      groupStart * 3,
+      (triangleMaterialIndices.length - groupStart) * 3,
+      currentMaterial ?? STAIR_SIDE_MATERIAL_INDEX,
+    )
+  }
+  geometry.setAttribute('uv2', new THREE.Float32BufferAttribute(uvs.slice(), 2))
   geometry.computeVertexNormals()
   return geometry
 }

packages/viewer/src/systems/stair/stair-materials.ts

@@ -0,0 +1,59 @@
+import {
+  getEffectiveStairSurfaceMaterial,
+  type StairNode,
+  type StairSegmentNode,
+} from '@pascal-app/core'
+import type * as THREE from 'three'
+import {
+  createMaterial,
+  createMaterialFromPresetRef,
+  DEFAULT_STAIR_MATERIAL,
+} from '../../lib/materials'
+
+export type StairBodyMaterials = [THREE.Material, THREE.Material]
+
+function createResolvedMaterial(
+  material: StairNode['material'] | StairSegmentNode['material'] | undefined,
+  materialPreset: string | undefined,
+): THREE.Material {
+  if (materialPreset) {
+    return createMaterialFromPresetRef(materialPreset) ?? DEFAULT_STAIR_MATERIAL
+  }
+
+  if (material) {
+    return createMaterial(material)
+  }
+
+  return DEFAULT_STAIR_MATERIAL
+}
+
+export function getStairBodyMaterials(stair: StairNode): StairBodyMaterials {
+  const tread = getEffectiveStairSurfaceMaterial(stair, 'tread')
+  const side = getEffectiveStairSurfaceMaterial(stair, 'side')
+
+  return [
+    createResolvedMaterial(tread.material, tread.materialPreset),
+    createResolvedMaterial(side.material, side.materialPreset),
+  ]
+}
+
+export function getStairRailingMaterial(stair: StairNode): THREE.Material {
+  const railing = getEffectiveStairSurfaceMaterial(stair, 'railing')
+  return createResolvedMaterial(railing.material, railing.materialPreset)
+}
+
+export function getStraightStairSegmentBodyMaterials(
+  segment: StairSegmentNode,
+  parentNode?: StairNode,
+): StairBodyMaterials {
+  if (segment.material !== undefined || typeof segment.materialPreset === 'string') {
+    const override = createResolvedMaterial(segment.material, segment.materialPreset)
+    return [override, override]
+  }
+
+  if (parentNode) {
+    return getStairBodyMaterials(parentNode)
+  }
+
+  return [DEFAULT_STAIR_MATERIAL, DEFAULT_STAIR_MATERIAL]
+}