This document describes the technical architecture of Rerun.
BUILD.mdrerun_py/README.md- build instructions for Python SDKCODE_OF_CONDUCT.mdCODE_STYLE.mdCONTRIBUTING.mdRELEASES.md
It all starts with logging. You can log rich data (point clouds, images, etc) with either our Python SDK or our Rust SDK.
The logging SDK:s encodes the data using Apache Arrow (see more below).
The logging data can be written to disk as .rrd files, or transmitted over TCP to either a Rerun Viewer or a Rerun Server.
The Rerun Viewer is where log data is visualized. It is usually run as a native app, but can also be compiled to WebAssembly (Wasm) and run in a browser.
The easiest way to launch the viewer is directly from the logging API with rr.init("rerun_example_app", spawn=True). However, the standalone viewer can also be run from the command line, for example to view an .rrd file: rerun mydata.rrd.
You can try running the viewer in a browser using rr.serve() in python, or using rerun --web-viewer mydata.rrd.
The web viewer consists of just a few small files - a thin .html, a .wasm blob, and an auto-generated .js bridge for the wasm. These files are served using the re_web_viewer_server crate.
The web viewer can load .rrd files (just drag-drop them into the browser), or read logging data streamed over WebSockets.
.rrd ("Rerun Data") is just a bunch of log messages appended one after the other to a file.
NOTE: .rrd files do not yet guarantee any backwards or forwards compatibility. One version of Rerun will likely not be able to open an .rrd file generated by another Rerun version.
Apache Arrow is a language-independent columnar memory format for arbitrary data. We use it to encode the log data when transmitting it over the network or storing it in an .rrd file. We also use it in our in-RAM data store, re_data_store.
In rust, we use the arrow2 crate.
The Rerun Viewer uses the wgpu graphics API. It provides a high-performance abstraction over Vulkan, Metal, D3D12, D3D11, OpenGLES, WebGL and WebGPU. This lets us write the same code graphics code for native as for web.
On web builds, we use WebGPU when available on the Web, but automatically fall back to a WebGL based emulation layer (with a more limited feature set).
We have written our own high-level rendering crate on top of wgpu, called re_renderer.
The GUI in the Rerun Viewer is using egui, a cross-platform, immediate mode GUI.
We use eframe, the egui framework, to run egui on both native and web.
Wasm (short for WebAssembly) is a binary instruction format supported by all major browser. The Rerun Viewer can be compiled to Wasm and run in a browser.
Threading support in Wasm is nascent, so care must we taken that we don't spawn any threads when compiling for wasm32.
Wasm has no access to the host system, except via JS calls (something that may change once WASI rolls out), so when compiling for wasm32 you can NOT use the Rust standard library to:
- Access files
- Read environment variables
- Get the current time (use
instantinstead) - Use networking (use
ehttp,reqwest, orewebsockinstead) - etc
The Rerun Viewer uses an immediate mode GUI, egui. This means that each frame the entire GUI is being laid out from scratch.
In fact, the whole of the Rerun Viewer is written in an immediate mode style. Each rendered frame it will query the in-RAM data store, massage the results, and feed it to the renderer.
The advantage of immediate mode is that is removes all state management. There is no callbacks that are called when some state has already changed, and the state of the blueprint is always in sync with what you see on screen.
Immediate mode is also a forcing function, forcing us to relentlessly optimize our code. This leads to a very responsive GUI, where there is no "hickups" when switching data source or doing time scrubbing.
Of course, this will only take us so far. In the future we plan on caching queries and work submitted to the renderer so that we don't perform unnecessary work each frame. We also plan on doing larger operation in background threads. This will be necessary in order to support viewing large datasets, e.g. several million points. The plan is still to do so within an immediate mode framework, retaining most of the advantages of stateless code.
Here is an overview of the crates included in the project:
| Crate | Description |
|---|---|
| rerun-cli | Rerun native CLI binary crate |
| rerun | Rerun Rust SDK and viewer shim crate |
| rerun_c | Rerun C SDK |
| rerun_py | Rerun Python SDK |
| re_sdk | Rerun logging SDK |
| Crate | Description |
|---|---|
| re_viewer | The Rerun viewer |
| re_viewport | The central viewport panel of the Rerun viewer. |
| re_time_panel | The time panel of the Rerun Viewer, allowing to control the displayed timeline & time. |
| re_data_ui | Provides ui elements for Rerun component data for the Rerun Viewer. |
| re_viewer_context | Rerun viewer state that is shared with the viewer's code components. |
| re_ui | Rerun GUI theme and helpers, built around egui |
| re_renderer | A wgpu-based renderer for all your visualization needs. |
| re_space_view | Types & utilities for defining Space View classes and communicating with the Viewport. |
| re_space_view_bar_chart | A Space View that shows a single bar chart. |
| re_space_view_dataframe | A Space View that shows the data contained in entities in a table. |
| re_space_view_spatial | Space Views that show entities in a 2D or 3D spatial relationship. |
| re_space_view_tensor | A Space View dedicated to visualizing tensors with arbitrary dimensionality. |
| re_space_view_text_document | A simple Space View that shows a single text box. |
| re_space_view_text_log | A Space View that shows text entries in a table and scrolls with the active time. |
| re_space_view_time_series | A Space View that shows plots over Rerun timelines. |
| Crate | Description |
|---|---|
| re_entity_db | In-memory storage of Rerun entities |
| re_query | Querying data in the re_data_store |
| re_types | The built-in Rerun data types, component types, and archetypes. |
| re_types_blueprint | The core traits and types that power Rerun's Blueprint sub-system. |
| re_log_encoding | Helpers for encoding and transporting Rerun log messages |
| Crate | Description |
|---|---|
| re_data_store | An in-memory time series database for Rerun log data, based on Apache Arrow |
| re_log_types | The basic building blocks of the Rerun data types and tables. |
| re_types_core | The core traits and types that power Rerun's data model. |
| re_format_arrow | Formatting of Apache Arrow tables |
| Crate | Description |
|---|---|
| re_sdk_comms | TCP communication between Rerun SDK and Rerun Server |
| re_web_viewer_server | Serves the Rerun web viewer (Wasm and HTML) over HTTP |
| re_ws_comms | WebSocket communication library (encoding, decoding, client, server) between a Rerun server and viewer |
| re_data_loader | Handles loading of Rerun data from file using data loader plugins |
| re_data_source | Handles loading of Rerun data from different sources |
| Crate | Description |
|---|---|
| re_build_info | Information about the build. Use together with re_build_tools |
| re_build_tools | build.rs helpers for generating build info |
| re_types_builder | Generates code for Rerun's SDKs from flatbuffers definitions. |
| re_dev_tools | Various tools for Rerun development. Each tool has a subcommand. |
| Crate | Description |
|---|---|
| re_analytics | Rerun's analytics SDK |
| re_log | Helpers for setting up and doing text logging in the Rerun crates. |
| re_error | Helpers for handling errors. |
| re_format | Miscellaneous tools to format and parse numbers, durations, etc. |
| re_tuid | 128-bit Time-based Unique Identifier |
| re_string_interner | Yet another string interning library |
| re_tracing | Helpers for tracing/spans/flamegraphs and such. |
| re_crash_handler | Detect panics and signals, logging them and optionally sending them to analytics. |
| re_smart_channel | A channel that keeps track of latency and queue length. |
| re_int_histogram | A histogram with i64 keys and u32 counts, supporting both sparse and dense uses. |
| re_memory | Run-time memory tracking and profiling. |
In order to get a dependency graph for our in-house crates and their docs, we recommend you run:
cargo install cargo-depgraph
cargo depgraph --all-deps --workspace-only --all-features --dedup-transitive-deps | dot -Tpng > deps.png
open deps.png
and:
cargo doc --no-deps --open
and then browse through the re_* crates.