# CZML data source - GTLF model disappears a certain camera angles

**URL:** <https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214>\
**Category:** General\
**Created:** [October 13, 2020, 3:34am UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214 "2020-10-13T03:34:21Z")\
**Posts on this page:** 14\
**Page:** 1

<div class="post-metadata">

**Author:** ![Emanuel\_Herrmann](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/emanuel_herrmann/32/3364_2.png) [@Emanuel\_Herrmann](https://community.cesium.com/u/Emanuel_Herrmann)\
**Post date:** [October 13, 2020, 3:34am UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/1 "2020-10-13T03:34:22Z")

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Hi all

I am seeing my model disappears at certain camera angles when it is close to the ground. I’ve read related posts about similar problems with 3Dtiles

> [@when zoom out or rotate viewer, my cesium model disappeared?](https://community.cesium.com/t/when-zoom-out-or-rotate-viewer-my-cesium-model-disappeared/6635/2):
>
> The tile is disappearing because its bounding volume is pretty small and is going out of view. It is the red area in the picture below (shown with tileset.debugShowBoundingVolume = true). Try making it larger to encompass the full model. [[image]](https://lh3.googleusercontent.com/-odi1VaJNu3w/WqCMB2XUepI/AAAAAAAACpw/2hKYczk4yfkAlmrwU8minCdY7So27fFMwCLcBGAs/s1600/bv.png)

pointing the problem to be the bounding volume. Is it possible to change the bounding volume of a gltf file?

I also tried to set debugShowBoundingVolume: true in the model, but the boundingVolume does not show.

Here is a zip of a screen recording  
[model disappears.mp4.zip](https://community.cesium.com/uploads/short-url/8tZFeXGijOtwtKbFv3TGbgc2PoC.zip) (2.5 MB)

My CZML

[

```
{
  id: "document",
  name: "CZML Path",
  version: "1.0",
  clock: {
    interval: `${begin}/${end}`,
    currentTime: begin,
    multiplier: 1,
  },
},
{
  id: "path",
  availability: `${begin}/${end}`,
  debugShowBoundingVolume: true,
  path: {
    material: {
      polygon: {
        color: {
          rgba: [255, 0, 255, 255],
        },
      },
    },
    width: 2,
    leadTime: 1,
    resolution: 1,
  },
  model: {
    id: "airplane",
    gltf: "./Cessna_172.gltf",
    debugWireframe: true,
    color: Cesium.Color.RED,
    debugShowBoundingVolume: true,
    nodeTransformations: {
      RootNode: {
        rotation: {
          unitQuaternion: [0, 0.7071, 0, 0.7071],
        },
      },
    },
  },
  viewFrom: {
    cartesian: [70, 20, 30], //
  },
  position: {
    interpolatitudeionAlgorithm: "LAGRANGE",
    interpolatitudeionDegree: 1,
    cartographicDegrees: [....],
  },
  orientation: {
    unitQuaternion: [....],
  },
},

```

];

Thanks in advance.

---

<div class="post-metadata">

**Author:** ![omar](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/omar/32/1999_2.png) [@omar](https://community.cesium.com/u/omar)\
**Post date:** [October 14, 2020, 2:16am UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/2 "2020-10-14T02:16:38Z")

</div>

The bounding volume issue shouldn’t apply here if you’re loading your model directly as a glTF, and not as a 3D Tileset I believe.

Are you able to share a Cesium scene with this model? You can upload it (along with the CZML) to your Cesium ion account and then share a link here. See: [https://cesium.com/docs/tutorials/import-3d-models/](https://cesium.com/docs/tutorials/import-3d-models/)

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<div class="post-metadata">

**Author:** ![Grant\_Rigby](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/grant_rigby/32/3892_2.png) [@Grant\_Rigby](https://community.cesium.com/u/Grant_Rigby)\
**Post date:** [January 19, 2021, 2:05am UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/3 "2021-01-19T02:05:16Z")

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Hi @omar, myself and @Emanuel_Herrmann have looked a bit deeper into this issue after the Christmas break and been able to reproduce this from the sandcastle code playground.

We were able to replicate the bug with both our own model and the model from the sandcastle. After this we tried hard coding the altitude to 0 in the datasource and found the issue was resolved, this lead us to log out the terrains metadata with `sampleTerrainMostDetailed(terrainProvider, positions)` and we think that the terrain tiles at in that area are rendering at a different hight that the metadata is reporting which is around 22 meters below sea level.

Sandcastle: [https://tinyurl.com/y6t4onyd](https://tinyurl.com/y6t4onyd)

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<div class="post-metadata">

**Author:** ![Grant\_Rigby](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/grant_rigby/32/3892_2.png) [@Grant\_Rigby](https://community.cesium.com/u/Grant_Rigby)\
**Post date:** [January 24, 2021, 8:59pm UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/4 "2021-01-24T20:59:07Z")

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Hi @omar, have you been able to take a look at this? Many thanks 🙂

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<div class="post-metadata">

**Author:** ![dzung](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/dzung/32/2996_2.png) [@dzung](https://community.cesium.com/u/dzung)\
**Post date:** [January 26, 2021, 5:28am UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/5 "2021-01-26T05:28:47Z")

</div>

The altitude in the datasource may have been sampled with respect to Cesium World Terrain. If you add the following line to the viewer constructor…

```auto
  terrainProvider: Cesium.createWorldTerrain()

```

…the Cesium aircraft’s altitude looks around 0.

It looks like you might also be running into this issue: [Depth plane causing clipping artifact · Issue #7879 · CesiumGS/cesium · GitHub](https://github.com/CesiumGS/cesium/issues/7879).

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<div class="post-metadata">

**Author:** ![Tao\_Lin](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/tao_lin/32/3987_2.png) [@Tao\_Lin](https://community.cesium.com/u/Tao_Lin)\
**Post date:** [January 27, 2021, 6:15am UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/6 "2021-01-27T06:15:48Z")

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Hi Dzung,

Thanks for your answer. I just add `terrainProvider: Cesium.createWorldTerrain()` to the sandbox. Now I can see half of the 3D model showing up, but half is still under the ground as the screenshot. Do we still miss something?

 ![Screen Shot 2021-01-27 at 7.06.25 PM](https://global.discourse-cdn.com/cesium/original/2X/8/89805f47bdf9c3f3161e8db36c77f813dff87d73.jpeg)

Thanks,

Tao

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<div class="post-metadata">

**Author:** ![dzung](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/dzung/32/2996_2.png) [@dzung](https://community.cesium.com/u/dzung)\
**Post date:** [January 29, 2021, 3:40pm UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/7 "2021-01-29T15:40:37Z")

</div>

It could be that the origin of the aircraft is at its center, so the height being 0 means that half of the aircraft should be underground.

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<div class="post-metadata">

**Author:** ![Tao\_Lin](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/tao_lin/32/3987_2.png) [@Tao\_Lin](https://community.cesium.com/u/Tao_Lin)\
**Post date:** [February 11, 2021, 9:06pm UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/8 "2021-02-11T21:06:34Z")

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Hi @dzung,

I believe this PR - [Fix for clipping and camera navigation issues below ellipsoid](https://github.com/CesiumGS/cesium/pull/9200) will fix our issue.

But I don’t see @omar or any Cesium staff review this PR for over 4 months. Could you follow up and let us know the progress, please?

Cheers,

Tao

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<div class="post-metadata">

**Author:** ![TomPovey](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/tompovey/32/1987_2.png) [@TomPovey](https://community.cesium.com/u/TomPovey)\
**Post date:** [February 12, 2021, 10:29am UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/9 "2021-02-12T10:29:00Z")

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> [@Tao\_Lin](#):
>
> I believe this PR - [Fix for clipping and camera navigation issues below ellipsoid](https://github.com/CesiumGS/cesium/pull/9200) will fix our issue.

+1 for more info on this please

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<div class="post-metadata">

**Author:** ![dzung](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/dzung/32/2996_2.png) [@dzung](https://community.cesium.com/u/dzung)\
**Post date:** [February 15, 2021, 4:57pm UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/10 "2021-02-15T16:57:07Z")

</div>

I have pushed for the PR to be assessed and merged.

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<div class="post-metadata">

**Author:** ![Akshay\_Kumar](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/akshay_kumar/32/3509_2.png) [@Akshay\_Kumar](https://community.cesium.com/u/Akshay_Kumar)\
**Post date:** [March 10, 2021, 6:58am UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/11 "2021-03-10T06:58:21Z")

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Hi Dzung, can you please provide an update on the status of the fix?

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<div class="post-metadata">

**Author:** ![Grant\_Rigby](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/grant_rigby/32/3892_2.png) [@Grant\_Rigby](https://community.cesium.com/u/Grant_Rigby)\
**Post date:** [March 15, 2021, 4:16am UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/12 "2021-03-15T04:16:28Z")

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Hi @dzung any update on this ticket? Is there something blocking this from being merged?

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<div class="post-metadata">

**Author:** ![dzung](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/dzung/32/2996_2.png) [@dzung](https://community.cesium.com/u/dzung)\
**Post date:** [March 18, 2021, 3:11pm UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/13 "2021-03-18T15:11:34Z")

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Hi all. Sorry for the delayed response. I am checking in with our team on the status of the PR.

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<div class="post-metadata">

**Author:** ![dzung](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/dzung/32/2996_2.png) [@dzung](https://community.cesium.com/u/dzung)\
**Post date:** [March 18, 2021, 3:28pm UTC](https://community.cesium.com/t/czml-data-source-gtlf-model-disappears-a-certain-camera-angles/11214/14 "2021-03-18T15:28:12Z")

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I have posted an update in the PR.