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Author Topic: Cesium 3D Tiles - Poor Overview Geometry & Texture Resolution  (Read 3741 times)

SP74

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Cesium 3D Tiles - Poor Overview Geometry & Texture Resolution
« on: October 18, 2018, 07:14:47 AM »
Hi,

I have produced a number of Tiled 3D Models and output them in both Photoscan tiled format, and Cesium 3D Tiles.  The Cesium 3D tiled models have poor geometry and low texture resolution when viewed at a zoomed out overview zoom level.  It is only once zoomed in that the geometry and texture resolution are acceptable.  The models vary in size from a few hundred input photos to a few thousand.  All display the same issues.  I have also loaded the models into 4DMapper, and the again when zoomed out poor results are obtained.

The models have been output using a mix of Photoscan 1.4.4 & Metashape.  The only noticeable difference is that a back (un rendered) side of the mesh is now transparent, so the model disappears when viewed from the back.  I am viewing the Cesium models using the cesium viewer (via html/apache web server).  I have tried numerous optimizations for the Cesium viewer, with little changes.

I have attached side by side comparisons of the 3D models, with the Photoscan model on the left and Cesium model on the right.

Cheers,

Stu.


SP74

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Re: Cesium 3D Tiles - Poor Overview Geometry & Texture Resolution
« Reply #1 on: October 25, 2018, 01:41:01 PM »
Hi,

Further to this issue the Cesium 3D tiles are not as sharp at maximum zoom as the Photoscan tiled model.  The attached example on the left shows the Photoscan model the right is the Cesium model.  It is most noticeable toward the bottom of the image.

Cheers,

Stu.

Alexey Pasumansky

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Re: Cesium 3D Tiles - Poor Overview Geometry & Texture Resolution
« Reply #2 on: November 08, 2018, 03:21:44 PM »
Hello Stu,

We were able to reproduce the lower quality zoom-level display when viewing the exported model in Cesium tiled format in the external viewer. In the next update we will try to adjust the zoom levels range in order to display better quality model (more detailed level) compared to the current implementation.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Alexey Pasumansky

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Re: Cesium 3D Tiles - Poor Overview Geometry & Texture Resolution
« Reply #3 on: November 09, 2018, 06:06:25 PM »
Hello Stu,

It seems that the best way to deal with this problem for the Cesium tiles exported from the current version is to modify the maximumScreenSpaceError parameter value for the tile layers and set it to 2 for PhotoScan export results (default value is 16).

(https://cesiumjs.org/Cesium/Build/Documentation/Cesium3DTileset.html)
Best regards,
Alexey Pasumansky,
Agisoft LLC

outsider

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Re: Cesium 3D Tiles - Poor Overview Geometry & Texture Resolution
« Reply #4 on: November 09, 2018, 07:15:39 PM »
Thank you for that Alexey!

I too have recently started using CesiumJS, and this information will come in handy!

SP74

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Re: Cesium 3D Tiles - Poor Overview Geometry & Texture Resolution
« Reply #5 on: November 10, 2018, 03:44:13 AM »
Hi Alexey,

That worked well, i had even better results setting maximumScreenSpaceError equal to 1.  The model looks great upon load and zooming in.  If you zoom out further the model geometry does start to degrade, this may become an issue for loading very large or multiple models. 

Thank you for pointing me in the direction of these additional parameters.  I will experiment further and provide my results next week.

Cheers,

Stu.