OGC feedback comments #329
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specification/README.md
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| * [Geometric error](#geometric-error) | ||
| * [Refinement](#refinement) | ||
| * [Additive](#additive) | ||
| * [Replacement](#replacement) |
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I just noticed that the order of Additive and Replacement in the table of contents is different than the order in the main text.
specification/README.md
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| "children": [...] | ||
| } | ||
| ``` | ||
| A tile's geometric error defines the selection metric for that tile. Its value is a nonnegative number specified, in meters, to be used by client implementation to calculate, along with other screen space metrics including the distance from the tile to the camera, the screen size and resolution, the SSE introduced if this tile is rendered and its children are not. If the introduced SEE exceeds the maximum allowed, the tile is refined and its children are considered for rendering. |
specification/README.md
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| `root` is an object that defines the root tile using the tile JSON described in the [above section](#tiles). `root.geometricError` is not the same as the tileset's top-level `geometricError`. The tileset's `geometricError` is used to determine the maximum error when the tileset is rendered and if its tiles should be considered for rendering; `root.geometricError` is used only to determine if the root tile is rendered. |
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The tileset's
geometricErroris used to determine the maximum error when the tileset is rendered and if its tiles should be considered for rendering;root.geometricErroris used only to determine if the root tile is rendered.
These two descriptions almost sound like they are doing the same thing. A more accurate summary is:
The tileset's
geometricErroris used to determine if the tileset's root tile is rendered;root.geometricErroris used to determine if the root's children are rendered.
specification/README.md
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| "children": [...] | ||
| } | ||
| ``` | ||
| A tile's geometric error defines the selection metric for that tile. Its value is a nonnegative number specified, in meters, to be used by client implementation to calculate, along with other screen space metrics including the distance from the tile to the camera, the screen size and resolution, the SSE introduced if this tile is rendered and its children are not. If the introduced SEE exceeds the maximum allowed, the tile is refined and its children are considered for rendering. |
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There should be a clear definition of geometric error that doesn't require defining it in context of screen space error.
Maybe something like this, which combines the implementation note:
A tile's geometric error defines the selection metric for that tile. Its value is a nonnegative number that specifies the error, in meters, of the tile's simplified representation of its source geometry. A root tile will generally have the greatest geometric error as it is generally the most simplified version of the source goemetry. Then each successive level of children has a lower geometric error than its parent, with leaf tiles generally having a geometric error of or close to 0.
Geometric error is used by client implementations to calculate, along with...
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used by client implementation to calculate, along with other screen space metrics including the distance from the tile to the camera, the screen size and resolution, the SSE introduced if this tile is rendered and its children are not
Grammatically this sentence is a little hard to follow.
specification/README.md
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| `root` is an object that defines the root tile using the JSON described in the [above section](#tiles). `root.geometricError` is not the same as the tileset's top-level `geometricError`. The tileset's `geometricError` is the error when the entire tileset is not rendered; `root.geometricError` is the error when only the root tile is rendered. | ||
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| `root.children` is an array of objects that define child tiles. Each child tile's content is fully enclosed by its parent tile's `boundingVolume` and, generally, a `geometricError` less than its parent tile's `geometricError`. For leaf tiles, the length of this array is zero, and `children` may not be defined. | ||
| `geometricError` is a nonnegative number that defines the error, in meters, that determines if the tileset is rendered. At runtime, the geometric error is used to compute _Screen-Space Error_ (SSE), the error measured in pixels. If the SSE does not exceed a required minimum, the tileset should not be rendered, and none of its tile should be considered for rendering, see [Geometric error](#geometric-error). |
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Thanks for the feedback @lilleyse, updated! |
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Looks great, thanks @ggetz. |
Edits to address feedback from OGC comment period.
Reordered the tiles section, added more explanation for geometric error and relation to SSE, and clarified tileset vs tile geometric error.
@lilleyse