# STDensify: Densify (m)LineString or (m)Polygon geometry objects

I have a densify function for my PL/SQL (Package and Object) code.

A SQL Server Spatial version exists as follows:

``` CREATE FUNCTION [\$(owner)].[STDensify] (
@p_geometry geometry,
@p_distance FLOAT,
@p_round_xy INT = 10,
@p_round_zm INT = 10
)
RETURNS geometry
AS
BEGIN
-- Implementation
END
GO
```

Description

This function add vertices to an existing vertex-to-vertex described (m)linestring or (m)polygon sdo_geometry.
New vertices are added in such a way as to maintain existing vertices, that is, no existing vertices are removed.
Densification occurs on a single vertex-to-vertex segment basis.
If segment length is < p_distance no vertices are added.
The implementation does not guarantee that the added vertices will be exactly p_distance apart; mostly they will be < @p_distance..
The implementation honours 3D and 4D shapes and averages these dimension values for the new vertices.
The function does not support compound objects or objects with circles, or described by arcs.
Any non (m)polygon/(m)linestring shape is simply returned as it is.

Arguments

``` @p_geometry (geometry) - (M)Linestring OR (m) polygon.
@p_distance    (FLOAT) - The desired optimal distance BETWEEN added vertices.
@p_round_xy      (INT) - DECIMAL degrees OF PRECISION TO which calculated XY ordinates are rounded.
@p_round_zm      (INT) - DECIMAL degrees OF PRECISION TO which ZM ordinates are compared.
```

Examples

Here are a selection of examples of how to call this function.

``` -- Densify 2D line into 4 segments
WITH DATA AS (
SELECT geometry::STGeomFromText('LINESTRING(0 0,10 10)',0) AS geom
)
SELECT [dbo].[STDensify](a.geom,a.geom.STLength()/4.0,3,2).AsTextZM() AS dGeom
FROM DATA AS a;
--
dGeom
LINESTRING (0 0, 2.5 2.5, 5 5, 7.5 7.5, 10 10)
--
-- Distance between all vertices is < 4.0
SELECT [dbo].[STDensify](geometry::STGeomFromText('LINESTRING (5 5, 5 7, 7 7, 7 5, 5 5)',0),4.0,3,2).AsTextZM() AS dGeom;
--
dGeom
LINESTRING (5 5, 5 7, 7 7, 7 5, 5 5)
--
-- Simple Straight line.
SELECT [\$(owner)].[STDensify] (geometry::STGeomFromText('LINESTRING(100 100,900 900.0)',0),125.0,3,2).AsTextZM() AS dGeom;
--
DGeom
LINESTRING (100 100, 188.889 188.889, 277.778 277.778, 366.667 366.667, 455.556 455.556, 544.444 544.444, 633.333 633.333, 722.222 722.222, 811.111 811.111, 900 900)
--
-- LineString with Z
SELECT [dbo].[STDensify] (geometry::STGeomFromText('LINESTRING(100 100 1.0,900 900.0 9.0)',0),125.0,3,2).AsTextZM() AS dGeom;
dGeom
LINESTRING (100 100 1, 180 180 1.8, 260 260 2.6, 340 340 3.4, 420 420 4.2, 500 500 5, 580 580 5.8, 660 660 6.6, 740 740 7.4, 820 820 8.2, 900 900 9)
--
-- LineStrings with ZM
SELECT [dbo].[STDensify] (geometry::STGeomFromText('LINESTRING(100.0 100.0 -4.56 0.99, 110.0 110.0 -6.73 1.1)',0),2.5,3,2).AsTextZM() AS dGeom;
dGeom
LINESTRING (100 100 -4.56 0.99, 101.667 101.667 -4.92 1.01, 103.333 103.333 -5.28 1.03, 105 105 -5.64 1.04, 106.667 106.667 -6.01 1.06, 108.333 108.333 -6.37 1.08, 110 110 -6.73 1.1)
--
GEOM
LINESTRING (1100.765 964.286, 1107.568 939.343, 1114.371 914.399, 1121.173 889.456, 1127.976 864.513, 1134.779 839.569, 1141.582 814.626, 1148.384 789.683, 1155.187 764.739, 1161.99 739.796, 1139.881 723.923, 1117.772 708.05, 1095.663 692.177, 1073.554 676.304, 1051.446 660.431, 1029.337 644.558, 1007.228 628.685, 985.119 612.812, 963.01 596.939, 941.032 610.675, 919.054 624.411, 897.076 638.148, 875.098 651.884, 853.12 665.62, 831.142 679.356, 809.164 693.093, 787.186 706.829, 765.208 720.565, 743.23 734.301, 721.252 748.038, 699.274 761.774, 677.296 775.51, 653.203 787.131, 629.11 798.753, 605.017 810.374, 580.924 821.995, 556.831 833.617, 532.738 845.238, 508.645 856.859, 484.552 868.481, 460.459 880.102, 434.63 869.26, 408.801 858.418, 382.972 847.576, 357.143 836.735, 331.314 825.893, 305.485 815.051, 279.656 804.209, 253.827 793.367, 242.53 770.043, 231.232 746.72, 219.935 723.396, 208.637 700.073, 197.34 676.749, 186.042 653.426, 174.745 630.102, 185.459 603.571, 196.173 577.041, 206.888 550.51, 217.602 523.98, 228.316 497.449, 253.543 500.85, 278.77 504.252, 303.996 507.653, 329.223 511.054, 354.45 514.456, 379.677 517.857, 404.903 521.258, 430.13 524.66, 455.357 528.061, 479.244 520.64, 503.131 513.219, 527.017 505.798, 550.904 498.377, 574.791 490.956, 598.678 483.534, 622.565 476.113, 646.452 468.692, 670.338 461.271, 694.225 453.85, 718.112 446.429, 717.262 420.493, 716.411 394.558, 715.561 368.622, 714.711 342.687, 713.86 316.751, 713.01 290.816, 698.66 270.089, 684.311 249.362, 669.962 228.635, 655.612 207.908, 641.263 187.181, 626.913 166.454, 612.564 145.727, 598.214 125, 573.271 120.181, 548.327 115.363, 523.384 110.544, 498.441 105.726, 473.497 100.907, 448.554 96.089, 423.611 91.27, 398.667 86.452, 373.724 81.633, 351.858 94.935, 329.992 108.236, 308.126 121.538, 286.261 134.84, 264.395 148.142, 242.529 161.443, 220.663 174.745, 198.797 188.047, 176.931 201.348, 155.065 214.65, 133.2 227.952, 111.334 241.254, 89.468 254.555, 67.602 267.857)
--
-- MultiLineString.
SELECT [dbo].[STDensify](geometry::STGeomFromText('MULTILINESTRING ((0 0, 5 5, 10 10),(20 20, 25 25, 30 30))',0),2.1,3,2).AsTextZM() AS dGeom;
--
dGeom
MULTILINESTRING ((0 0, 1.25 1.25, 2.5 2.5, 3.75 3.75, 5 5, 6.25 6.25, 7.5 7.5, 8.75 8.75, 10 10), (20 20, 21.25 21.25, 22.5 22.5, 23.75 23.75, 25 25, 26.25 26.25, 27.5 27.5, 28.75 28.75, 30 30))
--
-- Polygon
SELECT [dbo].[STDensify](
geometry::STGeomFromText('POLYGON((0 0,20 0,20 20,0 20,0 0),(10 10,10 11,11 11,11 10,10 10),(5 5,5 7,7 7,7 5,5 5))',0),
4.0,
3,2
).AsTextZM() AS dGeom;
dGeom
POLYGON ((0 0, 4 0, 8 0, 12 0, 16 0, 20 0, 20 4, 20 8, 20 12, 20 16, 20 20, 16 20, 12 20, 8 20, 4 20, 0 20, 0 16, 0 12, 0 8, 0 4, 0 0), (10 10, 10 11, 11 11, 11 10, 10 10), (5 5, 5 7, 7 7, 7 5, 5 5))
--
-- MultiPolygon
SELECT [dbo].[STDensify](
geometry::STGeomFromText('MULTIPOLYGON(((100 100,110 100,110 110,100 110,100 100)),((0 0,20 0,20 20,0 20,0 0),(10 10,10 11,11 11,11 10,10 10),(5 5,5 7,7 7,7 5,5 5)))',0),
4.0,
3,2
).AsTextZM() AS dGeom;
dGeom
MULTIPOLYGON (((100 100, 103.333 100, 106.667 100, 110 100, 110 103.333, 110 106.667, 110 110, 106.667 110, 103.333 110, 100 110, 100 106.667, 100 103.333, 100 100)), ((0 0, 4 0, 8 0, 12 0, 16 0, 20 0, 20 4, 20 8, 20 12, 20 16, 20 20, 16 20, 12 20, 8 20, 4 20, 0 20, 0 16, 0 12, 0 8, 0 4, 0 0), (10 10, 10 11, 11 11, 11 10, 10 10), (5 5, 5 7, 7 7, 7 5, 5 5)))
```

The function is available with the general package of SQL Server Spatial Functions here

I hope this function is of interest to someone.