2.12.0 Change Notes

Custom particle effects

The display system now makes it easy to implement particle effects using decorators. Particle effects simulate phenomena like fire, smoke, snow, and rain by animating hundreds or thousands of small particles. The new ParticleCollectionBuilder API allows such collections to be efficiently created and rendered.

The frontend-devtools package contains an example SnowEffect, as illustrated in the still image below. When applied to a viewport, the effect is animated, of course. Snow particle effect

Updated version of Electron

Updated recommended version of Electron from 10.1.3 to 11.1.0. Note that Electron is specified as a peer dependency in iModel.js - so it's recommended but not mandatory that applications migrate to this electron version.

IpcSocket for use with dedicated backends

For cases where a frontend and backend are explicitly paired (e.g. desktop and mobile apps), a more direct communication path is now supported via the IpcSocket api. See the Rpc vs Ipc learning article for more details.

External textures

By default, a tile containing textured materials embeds the texture images as JPEGs or PNGs. This increases the size of the tile, wasting bandwidth. A new alternative requires only the Id of the texture element to be included in the tile; the image can be requested separately. Texture images are cached, so the image need only be requested once no matter how many tiles reference it.

This feature is currently disabled by default. Enabling it requires the use of APIs currently marked @alpha. Pass to IModelApp.startup a TileAdmin with the feature enabled as follows:

  const tileAdminProps: TileAdmin.Props = { enableExternalTextures: true };
  const tileAdmin = TileAdmin.create(tileAdminProps);
  IModelApp.startup({ tileAdmin });

Changes to IModelDb.close and IModelDb.saveChanges

Previously, IModelDb.close would save any uncommitted changes to disk before closing the iModel. It no longer does so - instead, if uncommitted changes exist when the iModel is closed, they will be discarded. Applications should explicitly call either IModelDb.saveChanges to commit the changes or IModelDb.abandonChanges to discard them before calling close.

In rare circumstances, IModelDb.saveChanges may now throw an exception. This indicates a fatal condition like exhaustion of memory or disk space. Applications should wrap calls to saveChanges in a try-catch block and handle exceptions by terminating without making further use of the iModel. In particular, they should not attempt to call close, saveChanges, or abandonChanges after such an exception has occurred.

Breaking API Changes

Electron Initialization

The @beta API's for desktop applications to use Electron via the @itwin/core-electron package have been simplified substantially. Existing code will need to be adjusted to work with this version. The class ElectronManager has been removed, and it is now replaced with the classes ElectronBackend and ElectronFrontend.

To create an Electron application, you should initialize your frontend via:

  import { ElectronFrontend } from "@itwin/core-electron/lib/ElectronFrontend";
  ElectronFrontend.initialize({ rpcInterfaces });

And your backend via:

  import { ElectronBackend } from "@itwin/core-electron/lib/ElectronBackend";
  ElectronBackend.initialize({ rpcInterfaces });

Note that the class ElectronRpcManager is now initialized internally by the calls above, and you do not need to initialize it directly.

Update element behavior

In order to support partial updates and clearing an existing value, the update element behavior has been enhanced/changed with regard to how undefined values are handled. The new behavior is documented as part of the method documentation here:


GPU memory limits

The RenderGraphics used to represent a Tile's contents consume WebGL resources - chiefly, GPU memory. If the amount of GPU memory consumed exceeds that available, the WebGL context will be lost, causing an error dialog to be displayed and all rendering to cease. The TileAdmin can now be configured with a strategy for managing the amount of GPU memory consumed and avoiding context loss. Each strategy defines a maximum amount of GPU memory permitted to be allocated to tile graphics; when that limit is exceeded, graphics for tiles that are not currently being displayed by any Viewport are discarded one by one until the limit is satisfied or no more tiles remain to be discarded. Graphics are discarded in order from least-recently- to most-recently-displayed, and graphics currently being displayed will not be discarded. The available strategies are:

  • "default" - a "reasonable" amount of GPU memory can be consumed.
  • "aggressive" - a conservative amount of GPU memory can be consumed.
  • "relaxed" - a generous amount of GPU memory can be consumed.
  • "none" - an unbounded amount of GPU memory can be consumed - no maximum is imposed.

The precise amount of memory permitted by each strategy varies based on whether or not the client is running on a mobile device; see TileAdmin.mobileGpuMemoryLimits and TileAdmin.nonMobileGpuMemoryLimits for precise values. The application can also specify an exact amount in number of bytes instead.

The limit defaults to "default" for mobile devices and "none" for non-mobile devices. To configure the limit when calling IModelApp.startup, specify TileAdmin.Props.gpuMemoryLimits. For example:

  IModelApp.startup({ tileAdmin: TileAdmin.create({ gpuMemoryLimits: "aggressive" }) });

Separate limits for mobile and non-mobile devices can be specified at startup if desired; the appropriate limit will be selected based on the type of device the client is running on:

  IModelApp.startup({ tileAdmin: TileAdmin.create({
    gpuMemoryLimits: {
      mobile: "default",
      nonMobile: "relaxed",

To adjust the limit after startup, assign to TileAdmin.gpuMemoryLimit.

This feature replaces the @alpha TileAdmin.Props.mobileExpirationMemoryThreshold option.

Last Updated: 12 February, 2024