Asset Previews

If you want a specific file/asset type to have a custom Thumbnail/Inspector Preview, you can simply create an AssetPreview. An AssetPreview initializes its own Scene and Camera, rendering the Camera to the Preview output, so all you need to do is populate it and/or position the Camera to your liking.

Model Example

[AssetPreview( "mymdl" )]
public class PreviewMyModelResource : AssetPreview
{
	// The speed at which the model rotates. The length of a cycle in seconds is 1 / CycleSpeed
	public override float PreviewWidgetCycleSpeed => 0.2f;

	// This will evaluate a few frames and pick the one with the least alpha and most luminance for the thumbnail
	public override bool UsePixelEvaluatorForThumbs => true;

	public PreviewMyModelResource( Asset asset ) : base( asset )
	{
	}

	public override Task InitializeAsset()
	{
		// Get the resource from the asset
		var resource = Asset.LoadResource<MyModelResource>();

		// Get the Model from the resource
		var model = resource?.Model;
		if ( model is null )
		{
			return Task.CompletedTask;
		}

		// Make sure we are scoped to the preview scene
		using ( Scene.Push() )
		{
			// Create a new GameObject with a SkinnedModelRenderer component 
			PrimaryObject = new GameObject( true, "Model Preview" );
			PrimaryObject.WorldTransform = Transform.Zero;

			var modelRenderer = PrimaryObject.AddComponent<SkinnedModelRenderer>();
			modelRenderer.PlayAnimationsInEditorScene = true;
			modelRenderer.Model = model; // Set the model on the renderer

			// Center the scene around the model bounds, so the camera is positioned correctly
			SceneSize = model.Bounds.Size;
			SceneCenter = model.Bounds.Center;
		}

		return Task.CompletedTask;
	}
}

Texture Example

[AssetPreview( "mytex" )]
public class PreviewMyTextureResource : AssetPreview
{
	// Since we're only previewing a texture, we don't need to bother rendering a video
	public override bool IsAnimatedPreview => false;

	public PreviewMyTextureResource( Asset asset ) : base( asset )
	{
	}

	public override Task InitializeAsset()
	{
		// Get the resource from the asset
		var resource = Asset.LoadResource<MyTextureResource>();

		// Get the Texture from the resource
		var texture = resource?.Texture;
		if ( texture is null )
		{
			return Task.CompletedTask;
		}

		// Make sure we are scoped to the preview scene
		using ( Scene.Push() )
		{
			// Create a new GameObject with a SpriteRenderer component 
			PrimaryObject = new GameObject( true, "Texture Preview" );
			PrimaryObject.WorldTransform = Transform.Zero;

			var spriteRenderer = PrimaryObject.AddComponent<SpriteRenderer>();
			spriteRenderer.Texture = texture; // Set the texture on the renderer
			spriteRenderer.Size = 100;
		}

		return Task.CompletedTask;
	}

	public override void UpdateScene( float cycle, float timeStep )
	{
		base.UpdateScene( cycle, timeStep );

		// Override the Camera settings so the camera is fixed on the Texture
		Camera.Orthographic = true;
		Camera.OrthographicHeight = 100;
		Camera.WorldPosition = Vector3.Backward * 100;
		Camera.WorldRotation = Rotation.LookAt( Vector3.Forward );
	}
}