ST_As3dTiles - PolarDB - Alibaba Cloud Documentation Center

This topic describes the ST_As3dTiles function. This function converts a sfmesh object into the 3D Tiles format and stores the converted object in your database.

Syntax

boolean ST_As3dTiles(sfmesh sfmesh_object,  cstring table_name,  cstring options default '{}');

Return values

Return value	Description
true	Indicates that the data is exported as expected.
false	Indicates that the data is not exported.

Parameters

Parameter	Description
sfmesh_object	The sfmesh object that you want to convert.
table_name	The table name.
options	The options in JSON strings that you can configure.

Usage notes

This function converts a sfmesh object into the 3D Tiles format and stores the converted object in your database. Before you use the ST_As3dTiles function to convert the object, you must use the ST_ImportIFC function to import the object. For more information about the ST_ImportIFC function, see ST_ImportIFC.

The following table describes the options that you can configure.

Option	Type	Description	Default value	Example
schema	String	The schema of the required table.	public	ganos
project	String	The project name. The name is used as the project_name field value of each record.	-	project_1
parallel	Integer	The degree of parallelism (DOP). If you increase the DOP, data import is accelerated, but may consume a large amount of memory. You can specify an appropriate value based on the actual data or the running status of the database. The maximum value of this option is 16.	1	16
size_threshold	Integer	The splitting threshold. Unit: KB. Geometric objects larger than this threshold in size are split until each tile is smaller than this threshold in size.	2048	4096
srid	Integer	The spatial reference identifier (SRID) of the destination sfmesh object. If the SRID of the source sfmesh object is inconsistent with that of the destination sfmesh object, an error is reported. If you do not specify this option, the destination sfmesh object does not have an SRID.	-	2326
method	String	The splitting method. You can specify this option based on your business requirements. Valid values: oct: octree quad: quadtree bsp: BSP tree	oct	bsp
filter_percent	Float	The filtering ratio. Valid values: `0 to 1`. If the filtering ratio is 10% (0.1), objects whose volume is less than 10% of tile volume are excluded for each non-leaf node tile.	0.1	0.01
tileset_prefix	String	The prefix of the 3D Tiles tileset endpoint.	-	http://your_server/foo/bar
enable_tile_option	Boolean	Specifies whether to enable the built-in tile attributes of a sfmesh object.	false	true
merge_material	Boolean	Specifies whether to merge the geometry with the same material. If this option is set to true, the file volume may be reduced.	true	false
with_extension	Boolean	Specifies whether to add a suffix to the URI of B3DM/Tileset in the generated tileset file. If this option is set to true, a suffix is added to the URL.	false	true
vertex_threshold	Float	The vertex merge threshold. If this option is set to 0, no vertex merge operation is performed. Otherwise, points whose vertex spacing is less than the threshold in each tile are merged.	0.0001	0.01
update_normal	Boolean	Specifies whether to re-calculate the normal data.	false	true
divide_factor	Float	The calculation factor of geometricError.	5	10

If you enable threshold-based vertex merge, original normal data is deleted. To ensure that the newly merged geometry maintains accurate shading and lighting attributes after the vertex merge, you can enable the update_normal option to re-calculate the normal data.
After you enable threshold-based vertex merge and the system re-calculates the normal data, the display effect may vary based on the vertex merge threshold.
When the system re-calculates the normal data of an object that has no such data, the generated volume value increases.
If geometricError generated for non-leaf nodes is excessively large, you can modify the divide_factor option. For example, you can double the value of the divide_factor option. In this case, geometricError is reduced by half.

After the project is imported to your database, the following tables are generated in the database:

[table_name]: the primary table that stores the tile metadata.
[table_name]_tile: the tile table that stores all tile data of the project.
[table_name]_tileset: the table that stores details about tileset.json corresponding to the project.

Structure of the [table_name] table:

Field	Type	Description	Remarks
project_id	uuid	The project ID.	The project ID is automatically generated
project_name	text	The project name.	If you do not specify this field, the project name column does not contain data. In most cases, the table is used to store the tables of multiple sub-projects.
srid	integer	This field is left empty.	-
anchor	geometry	The 3D point at which the project is anchored.	The center point projection of the sfmesh project is transformed into the WGS 84 coordinate system.
extent	geometry	This field is left empty.	-
aux	text	This field is left empty.	-
tiletable	varchar(64)	This field is left empty.	-

Structure of the [table_name]_tile table:

Field	Type	Description	Remarks
project_id	uuid	The project ID.	The project ID is the same as that of the [table_name] table.
project_name	text	The project name.	The project name is the same as that of the [table_name] table.
uid	uuid	The tile ID.	The tile ID is automatically generated.
lod	integer	This field is left empty.	-
parent	uuid	This field is left empty.	-
children	uuid[]	This field is left empty.	-
aux	jsonb	This field is left empty.	-
tile	scene	The entity of the tile.	-

Structure of the [table_name]_tileset table:

Field	Type	Description	Remarks
project_id	uuid	The project ID.	The project ID is the same as that of the [table_name] table.
project_name	text	The project name.	The project name is the same as that of the [table_name] table.
uid	uuid	The ID of `tileset.json`.	If the node is the root node of the project, the field value is the same as the value of the project_id field.
tileset	jsonb	The entity of `tileset.json`.	-

Examples

SELECT ST_As3dTiles(sfmesh_obj, 'test_table') 
FROM t_sfmesh
WHERE id = 1;

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Parallel

SELECT ST_As3dTiles(sfmesh_obj, 'test_table', '{"parallel": 2}') 
FROM t_sfmesh
WHERE id = 1;

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More options

SELECT ST_As3dTiles(sfmesh_obj, 'test_table', '{"project":"test_proj", "method":"oct", "size_threshold":20}') 
FROM t_sfmesh
WHERE id = 1;

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