How to make the EmphasizeElements class act on ExternalIModels

[peiyanlu]

I attached an additional iModel to the current viewport by customizing the TiledGraphicsProvider, which displays normally, but some APIs do not work on it, such as EmphasizeElements. I want to achieve element isolation and hiding. When I try to specify an element, it displays as expected, but I don't know how to let the EmphasizeElements API handle the selected element on its own

import { AxisAlignedBox3d, QueryRowFormat } from '@itwin/core-common'
import {
  FeatureSymbology,
  IModelConnection,
  SceneContext,
  ScreenViewport,
  SpatialModelState,
  TiledGraphicsProvider,
  TileTreeReference,
  Viewport,
} from '@itwin/core-frontend'
import { Range3d } from '@itwin/core-geometry'


class AppTileTreeReference extends TileTreeReference {
  private readonly _ref: TileTreeReference
  private readonly _overs: FeatureSymbology.Overrides
  
  public constructor(ref: TileTreeReference, overs: FeatureSymbology.Overrides) {
    super()
    this._ref = ref
    this._overs = overs
  }
  
  public get treeOwner() {
    return this._ref.treeOwner
  }
  
  public override addToScene(context: SceneContext): void {
    const tree = this.treeOwner.load()
    if (undefined === tree) return
    
    // ###TODO transform
    const args = this.createDrawArgs(context)
    if (undefined === args) return
    
    tree.draw(args)
    
    args.graphics.symbologyOverrides = this._overs
    const branch = context.createBranch(args.graphics, args.location)
    context.outputGraphic(branch)
  }
  
  public override get castsShadows() {
    return this._ref.castsShadows
  }
}

export class AppTiledGraphicsProvider implements TiledGraphicsProvider {
  public readonly vp: Viewport
  public readonly iModel: IModelConnection
  private readonly _refs: TileTreeReference[] = []
  
  protected constructor(vp: Viewport, iModel: IModelConnection, overs: FeatureSymbology.Overrides) {
    this.vp = vp
    this.iModel = iModel
    for (const model of iModel.models) {
      const spatial = model.asSpatialModel
      if (undefined !== spatial) {
        const ref = spatial.createTileTreeReference(vp.view)
        this._refs.push(new AppTileTreeReference(ref, overs))
      }
    }
  }
  
  public static async create(vp: ScreenViewport, iModel: IModelConnection): Promise<AppTiledGraphicsProvider> {
    const query = { from: SpatialModelState.classFullName, wantPrivate: false }
    const props = await iModel.models.queryProps(query)
    
    const modelIds = []
    for (const prop of props) if (undefined !== prop.id) modelIds.push(prop.id)
    
    await iModel.models.load(modelIds)
    
    // Enable all categories (and subcategories thereof)
    const ecSql: string = `SELECT DISTINCT Category.Id AS CategoryId FROM BisCore.GeometricElement3d WHERE Category.Id IN (SELECT ECInstanceId from BisCore.SpatialCategory)`
    const reader = iModel.createQueryReader(ecSql, undefined, { rowFormat: QueryRowFormat.UseJsPropertyNames })
    const catIds: string[] = (await reader.toArray()).map(k => k.categoryId)
    
    const subCatsRequest = iModel.subcategories.load(catIds)
    if (undefined !== subCatsRequest) await subCatsRequest.promise
    
    // Ignore the symbology overrides defined on the viewport - instead, set up our own to draw our iModel's categories
    const overs = new FeatureSymbology.Overrides(vp)
    
    // TODO 
    // overs.setNeverDrawnSet(new Set([ '0x9de5', '0x7209' ]))
    // vp.setNeverDrawn(new Set([ '0x9de5', '0x7209' ]))
    
    for (const catId of catIds) {
      const subCats = iModel.subcategories.getSubCategories(catId)
      if (undefined !== subCats) {
        for (const subCat of subCats) {
          overs.setVisibleSubCategory(subCat)
        }
      }
    }
    
    return new AppTiledGraphicsProvider(vp, iModel, overs)
  }
  
  public forEachTileTreeRef(_vp: Viewport, func: (ref: TileTreeReference) => void): void {
    for (const ref of this._refs) func(ref)
  }
  
  public isLoadingComplete() {
    for (const ref of this._refs) {
      if (!ref.isLoadingComplete) return false
    }
    
    return true
  }
}

[pmconne]

EmphasizeElements applies FeatureSymbology.Overrides to the view. In the line below, you are replacing the view's overrides with your own.

args.graphics.symbologyOverrides = this._overs

If that was what you actually wanted to do, the "right" way is to override TileTreeReference.getSymbologyOverrides.

If you want the view's overrides to apply to your tile tree, don't provide your own overrides.
If you want to selectively customize how the view's overrides are applied to your tile tree, implement TileTreeReference.getAppearanceProvider, perhaps using FeatureAppearanceProvider.supplement or FeatureAppearanceProvider.chain.

[peiyanlu]

Thank you for your reply, but I still have some questions. I have found that if the two iModels are completely unrelated and do not provide a new FeatureSymbology Overrides, it will not display properly in the viewport, right?

[pmconne]

Right, elements and models and categories and so on are identified by Id, if the same Id means two different things in two different iModels then things will misbehave.

[peiyanlu]

Thank you for your help