How to limit the loading distance of Cesium

1532167917 · July 19, 2024, 9:29am

I’ve found that Cesium has an infinite loading distance in unity. My 3dtile file size is huge, so the frame rate will be low when all of them are loaded.

How do I limit the loading distance of Cesium in Unity?

1532167917 · July 22, 2024, 12:51pm

I used a very foolish approach.
Enable the “Show Tiles In Hierarchy” option.

Calculate the distance from all mesh to the camera anchor point, and then enable and disable the “Mesh Renderer” component

janine · July 22, 2024, 2:34pm

Hi @1532167917, welcome to the community!

I’m glad you found a solution that works for you. I’d still like to leave some tips in case this continues to be a problem, or if the needs of your application change.

First, Cesium does not actually have an infinite loading distance. The distance depends on the frustum size of the Main Camera. You could technically adjust the Near / Far clip planes to change this, but that will affect how the camera renders the entire scene, so that may not be desired.

Secondly, 3D Tiles is meant to optimize streaming a lot of data. If you’re experiencing frame rate issues, you can always increase the Maximum Screen Space Error value on your tileset. That will lessen the amount of detail that the tileset attempts to load. You can also decrease the Maximum Simultaneous Tile Loads, which will affect the number of tiles that are loading in the background.

Third, we offer a tile exclusion interface called CesiumTileExcluder, which allows you to exclude tiles based on custom C# logic. This pull request contains an example of how to implement this interface.

github.com/CesiumGS/cesium-unity

Add ability to exclude tiles by implementing a C# class.

CesiumGS:main ← CesiumGS:tile-excluder

opened 06:03AM - 16 Mar 23 UTC

kring

+522 -59

Depends on CesiumGS/cesium-native#608 Added `CesiumTileExcluder`, which is a …C# version of cesium-native's `ITileExcluder`. The idea is that we can add a C# class like this to our project: ```csharp using CesiumForUnity; using UnityEngine; [RequireComponent(typeof(BoxCollider))] public class CesiumBoxExcluder : CesiumTileExcluder { private BoxCollider _boxCollider; private Bounds _bounds; public bool invert = false; protected override void OnEnable() { this._boxCollider = this.gameObject.GetComponent<BoxCollider>(); this._bounds = new Bounds(this._boxCollider.center, this._boxCollider.size); base.OnEnable(); } protected void Update() { this._bounds.center = this._boxCollider.center; this._bounds.size = this._boxCollider.size; } public bool CompletelyContains(Bounds bounds) { return Vector3.Min(this._bounds.max, bounds.max) == bounds.max && Vector3.Max(this._bounds.min, bounds.min) == bounds.min; } public override bool ShouldExclude(Cesium3DTile tile) { if (!this.enabled) { return false; } if (this.invert) { return this.CompletelyContains(tile.bounds); } return !this._bounds.Intersects(tile.bounds); } } ``` And then add an instance of this class as a component on the `Cesium3DTileset` or any of its parents, up to and including the `CesiumGeoreference`. With that in place, cesium-native will call the `ShouldExclude` method for each tile that it is considering loading or rendering. This will happen a _lot_, so this method needs to be fast. Return true to skip loading and rendering that tile. Return false to load it and render it as normal. In the implementation above, a user-defined BoxCollider is also attached to the same GameObject as the CesiumBoxExcluder. Any tiles that intersect this BoxCollider are loaded and rendered, others are not. So tiles that are entirely outside of the box are ignored. The given tile's `bounds` property is an axis-aligned bounding box in the same coordinate system as the `CesiumBoxExcluder`, so it's easy to do tests like this. In this screenshot, the BoxCollider is the green box in the middle of Melbourne. All of the visible tiles are at least partially inside the box: ![image](https://user-images.githubusercontent.com/924374/225528568-647a9bb8-58c1-4635-b0dc-c24713b7ff95.png) If we disable the CesiumBoxExcluder, all the tiles load as normal: ![image](https://user-images.githubusercontent.com/924374/225528858-5986386f-7413-434f-8050-37d5ff1bc61c.png) Also in this PR: Extended Reinterop to allow constructors of blittable value types to be called from C++. On the C++ side, these are exposed as `Constrct` methods rather than C++ constructors so that brace initialization can continue to be used to initialize fields without calling into C#.

The CesiumTileExcluder can do what you’re already doing, but a bit more robustly – it can save a bit on performance, because it won’t try to handle tiles that are entirely excluded.

Let us know if you have any follow-up questions!

1532167917 · July 24, 2024, 2:26am

Thanks, that’s exactly what I needed.

krumelmonster · September 1, 2024, 8:57am

Disabling the mesh renderer should be a last resort.
It would be nicer to set the LOD level of the tiles by distance. Is that possible?

Kevin_Ring · September 6, 2024, 9:12am

@krumelmonster selecting LOD based on distance is default behavior. Can you clarify what you’re looking for?

Technically, LOD is selected by projection of the geometric error onto the screen, which will roughly correspond to distance.

Cutting off rendering at a particular distance is not currently supported, if that’s what you’re after. We get this request a lot, but it won’t actually help as much as people think it will. LOD drops off rapidly in the distance, so cutting off distant tiles entirely will only reduce rendering load very slightly. Reducing the maximum screen-space error, on the other hand, will drastically reduce the time it takes to load and render (at the cost of quality).

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How to limit the loading distance of Cesium

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