# Cesium collapses when i press "simulate" button in Unreal **URL:** \ **Category:** Cesium for Unreal\ **Created:** [March 19, 2023, 11:25am UTC](https://community.cesium.com/t/cesium-collapses-when-i-press-simulate-button-in-unreal/22946 "2023-03-19T11:25:54Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Tibor\_Venosz](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/tibor_venosz/32/12453_2.png) [@Tibor\_Venosz](https://community.cesium.com/u/Tibor_Venosz)\ **Post date:** [March 19, 2023, 11:25am UTC](https://community.cesium.com/t/cesium-collapses-when-i-press-simulate-button-in-unreal/22946/1 "2023-03-19T11:25:54Z")
Cesium collapses when i press “simulate” button in Unreal What cause this and how to avoid? (the world terrain disappear) ---
**Author:** ![Kevin\_Ring](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/kevin_ring/32/2003_2.png) [@Kevin\_Ring](https://community.cesium.com/u/Kevin_Ring)\ **Post date:** [March 19, 2023, 11:37pm UTC](https://community.cesium.com/t/cesium-collapses-when-i-press-simulate-button-in-unreal/22946/2 "2023-03-19T23:37:30Z")
In Simulate mode, only cameras in the level are used to select tiles. The Editor camera that is shown in the viewport is intentionally not used to select which parts of the model to show (and their level-of-detail). So if you don’t have any cameras in the level, or if they’re far away from where the viewport is looking, you’ll see nothing. ---
**Author:** ![Tibor\_Venosz](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/tibor_venosz/32/12453_2.png) [@Tibor\_Venosz](https://community.cesium.com/u/Tibor_Venosz)\ **Post date:** [March 20, 2023, 6:50pm UTC](https://community.cesium.com/t/cesium-collapses-when-i-press-simulate-button-in-unreal/22946/3 "2023-03-20T18:50:43Z")
It doesnt solve anything. I put the camera and still see nothing. Please provide me more information what to do becouse any time i press simulate literally ALL the terrain disappear. Doesnt matter if there is a camera or not or the camera is selected in the view or not. Thanks. ---
**Author:** ![Kevin\_Ring](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/kevin_ring/32/2003_2.png) [@Kevin\_Ring](https://community.cesium.com/u/Kevin_Ring)\ **Post date:** [March 21, 2023, 3:39am UTC](https://community.cesium.com/t/cesium-collapses-when-i-press-simulate-button-in-unreal/22946/4 "2023-03-21T03:39:27Z")
I don’t know why that would happen. Does the same thing happen in the Cesium for Unreal Samples project, or only in your own project? ---
**Author:** ![Tibor\_Venosz](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/tibor_venosz/32/12453_2.png) [@Tibor\_Venosz](https://community.cesium.com/u/Tibor_Venosz)\ **Post date:** [March 23, 2023, 8:45pm UTC](https://community.cesium.com/t/cesium-collapses-when-i-press-simulate-button-in-unreal/22946/5 "2023-03-23T20:45:40Z")
Yes, i made a test and half of the world disappear also in the sample projects when i press simulate. Please give me a detailed description about how to avoid this. Could you? Kevin Ring via Cesium Community \<[notifications@cesium.discoursemail.com](mailto:notifications@cesium.discoursemail.com)\> ezt írta (időpont: 2023. márc. 21., K, 3:49): ---
**Author:** ![Kevin\_Ring](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/kevin_ring/32/2003_2.png) [@Kevin\_Ring](https://community.cesium.com/u/Kevin_Ring)\ **Post date:** [March 23, 2023, 11:01pm UTC](https://community.cesium.com/t/cesium-collapses-when-i-press-simulate-button-in-unreal/22946/6 "2023-03-23T23:01:34Z")
This is sort of working as intended, but admittedly confusing. It’s not obvious to me how it _should_ work… In a Simulate session, the Editor camera does not affect tile selection. This is useful if you want to use the Editor camera to examine the world as it really is without affecting it. It’s the same as starting a normal Play-in-Editor and then clicking the Eject button. You can fly the Editor camera around and see the actual state of the world, including the missing parts of the globe that aren’t drawn because no in-game camera can see them. This is often useful, and I wouldn’t want to change it! And I’m not sure if we can distinguish between these two modes (“Play plus eject” versus “Simulate”). Similarly, in Simulate mode, you can move the player pawn and watch the tile selection change. Or you can possess it and the tile selection will update live. But it sounds like you’re expecting to see a normal globe in the Editor view. I guess I don’t understand the potential use-cases here well enough to say how this all should work. Maybe you can tell us a bit more about what you’re using Simulate mode for. ---
**Author:** ![Tibor\_Venosz](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/tibor_venosz/32/12453_2.png) [@Tibor\_Venosz](https://community.cesium.com/u/Tibor_Venosz)\ **Post date:** [March 24, 2023, 12:08am UTC](https://community.cesium.com/t/cesium-collapses-when-i-press-simulate-button-in-unreal/22946/7 "2023-03-24T00:08:04Z")
As i see in any case i touch “simulate” button it wreck up my scene and the tiles doesnt load anymore in render or game. So the best is to just never touch simulate. Now i made a test, i had to recover all the project and after just hit “play” i got the same results i need. Sorry for ping you with this and thanks for the fast assistance! Thank you. ---
**Author:** ![\_RU](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/_ru/32/12437_2.png) [@\_RU](https://community.cesium.com/u/_RU)\ **Post date:** [April 11, 2023, 4:57am UTC](https://community.cesium.com/t/cesium-collapses-when-i-press-simulate-button-in-unreal/22946/8 "2023-04-11T04:57:23Z")
![Screenshot_1](https://global.discourse-cdn.com/cesium/original/2X/2/2d9ee0c48241fb755ca1d3f1477823b5438edf6f.jpeg) Just like this.