# Sentis

The ML-Agents Toolkit allows you to use pre-trained neural network models inside your Unity games. This support is possible thanks to [Sentis](https://docs.unity3d.com/Packages/com.unity.ai.inference@latest). Sentis uses [compute shaders](https://docs.unity3d.com/Manual/class-ComputeShader.html) to run the neural network within Unity.

## Supported devices

Sentis supports [all Unity runtime platforms](https://docs.unity3d.com/Manual/PlatformSpecific.html).

Scripting Backends : Sentis is generally faster with **IL2CPP** than with **Mono** for Standalone builds. In the Unity Editor, you can't use Sentis with GPU device selected with Editor Graphics Emulation set to **OpenGL(ES) 3.0 or 2.0 emulation**. Also, there might be non-fatal build time errors when target platform includes Graphics API that does not support **Unity Compute Shaders**.

In cases when it is not possible to use compute shaders on the target platform, inference can be performed using **CPU** or **GPUPixel** Sentis backends.

## Using Sentis

When using a model, drag the model file into the **Model** field in the Inspector of the Agent. Select the **Inference Device**: **Compute Shader**, **Burst** or **Pixel Shader** you want to use for inference.

**Note:** For most of the models generated with the ML-Agents Toolkit, CPU inference (**Burst**) will be faster than GPU inference (**Compute Shader** or **Pixel Shader**). You should use GPU inference only if you use the ResNet visual encoder or have a large number of agents with visual observations.

# Unsupported use cases
## Externally trained models
The ML-Agents Toolkit only supports the models created with Unity's trainers. Model loading expects certain conventions for constants and tensor names. While you can construct a model that follows these conventions, Unity doesn't provide any additional help for this. You can find more details in [TensorNames.cs](https://github.com/Unity-Technologies/ml-agents/blob/release/4.0.0/com.unity.ml-agents/Runtime/Inference/TensorNames.cs) and [SentisModelParamLoader.cs](https://github.com/Unity-Technologies/ml-agents/blob/release/4.0.0/com.unity.ml-agents/Runtime/Inference/SentisModelParamLoader.cs).

> [!NOTE]
> If you want to run inference on an externally trained model, use Sentis directly, instead of trying to run it through ML-Agents.

## Model inference outside of Unity

We do not provide support for inference anywhere outside of Unity. The `.onnx` files produced by training use the open format ONNX; if you wish to convert a `.onnx` file to another format or run inference with them, refer to their documentation.