# How to compute the geometricError in 3d-tiles?

Hi anyone,

I have a lot of models that have already been split in tiles, as the fllowing example,
https://github.com/AnalyticalGraphicsInc/3d-tiles/blob/master/examples/tileset.json,

I build the tileset.json, but I don't know how to compute it's geometricError.

Can someone give me some tips? be deeply grateful！

Hi,

The geometric error defines the error, in meters, when a tile is rendered, but its children are not. So, for example, this is zero for leaf tiles because their contents represent the original dataset at full resolution.

For non-leaf tiles, the geometric error depends on the type of data (e.g., buildings, point clouds, terrain, etc.) and how significantly it was decimated (e.g., buildings that were removed, points that were removed, vertices that were merged creating a lower level of detail). For a concrete example for terrain, see the Hausdorff distance in Slide 17 of Rendering the Whole Wide World on the World Wide Web.

Patrick

Patrick Cozzi於 2016年6月1日星期三 UTC+8下午8時05分34秒寫道：

Hi,

The geometric error defines the error, in meters, when a tile is rendered, but its children are not. So, for example, this is zero for leaf tiles because their contents represent the original dataset at full resolution.

For non-leaf tiles, the geometric error depends on the type of data (e.g., buildings, point clouds, terrain, etc.) and how significantly it was decimated (e.g., buildings that were removed, points that were removed, vertices that were merged creating a lower level of detail). For a concrete example for terrain, see the Hausdorff distance in Slide 17 of Rendering the Whole Wide World on the World Wide Web.

Patrick

On Tuesday, May 31, 2016 at 4:53:12 AM UTC-4, biceal...@gmail.com wrote:Hi anyone,

I have a lot of models that have already been split in tiles, as the fllowing example,

``````    https://github.com/AnalyticalGraphicsInc/3d-tiles/blob/master/examples/tileset.json,
``````

I build the tileset.json, but I don't know how to compute it's geometricError.

Can someone give me some tips? be deeply grateful！

Hi Patrick,

Is the geometric error(in meters) a distance between something? like, distance between the viewer and object?
I still dont't understand why the unit of geometric error is about length.

Thanks!

The geometric error can be computed however you like, but often a good estimate is finding the diagonal of the largest building/feature in the tile. In tileset.json a tile’s geometric error will often equal the largest geometric error of its children. Typically leaf tiles have a geometric error of 0.

Thanks,

Gabby