# What is Scene Understanding?

**Scene Understanding** is an advanced **feature of Spatial Awareness** that gives **HoloLens 2** developers a structured, high-level **environment representation**.

Your mixed reality device is constantly integrating information about what it sees in your environment. Scene Understanding funnels all of these data sources and produces **one single cohesive abstraction**.

With Scene Understanding, you can rely on the system to tell you when it has detected certain **surfaces** and identify the surfaces as **walls, floors, ceilings**, and **platforms**. Scene Understanding creates a watertight mesh of your environment, even if you haven't scanned it completely.

{% hint style="danger" %}
Note that Scene Understanding SDK is only available for **HoloLens 2**.
{% endhint %}

The goal of **Scene understanding** is to **transform** the **un-structured environment sensor data** that your Mixed Reality device captures and to convert it into a powerful, but abstracted, representation that is intuitive and easy to develop for. [The Scene Understanding SDK](https://aka.ms/UnitySceneUnderstandingSDK) acts as the communication layer between your application and the Scene Understanding runtime. It's aimed to mimic existing standard constructs such as 3D scene graphs for 3D representations and 2D rectangles and panels for 2D applications. In general, Scene Understanding is **framework agnostic,** allowing for[ **interop**](/mixed-reality-docs/glossary.md#interoperability) between varied frameworks that interact with it.

![Common spatial mapping usage scenarios: placement, occlusion, physics and navigation.](/files/-M3Dnw_vU76PVhfeP5kt)

{% hint style="info" %}
The process of converting the raw sensor data into a Scene is a potentially **expensive operation** that could take seconds for **medium spaces (\~10x10m)** to minutes for **very large spaces (\~50x50m),** and therefore it is not something that is being computed by the device without application **request.**
{% endhint %}

Many of the core scenarios for environmentally aware applications, for example **placement of objects**, creating **occlusion** for a virtual object and running **physics simulations** that takes into account of the virtual objects and your environment are addressable by both Spatial Mapping and Scene Understanding. There are few **differences** you need to consider before deciding which one to use for your application. A core difference between Scene understanding and Spatial mapping is a **trade-off** of **maximal accuracy** and **latency** to **structure** and **simplicity**. If your application requires the **lowest-latency** possible and mesh triangles that only you will want to access, use **Spatial Mapping** directly. If you are performing **higher level processing**, you may consider switching to the **Scene understanding** model as it should provide you with a super-set of spatial mapping functionality. Also note that because Scene understanding provides a **snapshot of the spatial mapping mesh** as part of its representation, you will always have access to the most complete and accurate spatial mapping data possible.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://www.xrdev.app/mixed-reality-docs/lessons/lesson-10/concepts/scene-understanding.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.