[raster] ST_Hillshade output can be wrong

[dustymugs]

The following doesn't return the correct answers.

WITH foo AS (
	SELECT
		ST_SetValue(
			ST_SetValue(
				ST_SetValue(
		ST_SetValue(
			ST_SetValue(
				ST_SetValue(
		ST_SetValue(
			ST_SetValue(
				ST_SetValue(
					ST_AddBand(ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0), 1, '32BF', 1, -9999),
					1, 2, 2, 2
				),
				1, 3, 2, 2
			),
			1, 4, 2, 2
		),
					1, 2, 3, 2
				),
				1, 3, 3, 3
			),
			1, 4, 3, 2
		),
					1, 2, 4, 2
				),
				1, 3, 4, 2
			),
			1, 4, 4, 2
		) AS rast
), bar AS (
	SELECT
		ST_Slope(rast, 1, '32BF') AS slope,
		ST_Aspect(rast, 1, '32BF') AS aspect,
		ST_Hillshade(rast, 1, '32BF', 1.75 * pi(), pi() / 4) AS hillshade
	FROM foo
)
SELECT
	x, y, val
FROM (
	SELECT
		(ST_PixelAsPolygons(hillshade)).*
	FROM bar
) baz

results in

 x | y |       val        
---+---+------------------
 1 | 1 |                 
 1 | 2 |                 
 1 | 3 |                 
 1 | 4 |                 
 1 | 5 |                 
 2 | 1 |                 
 2 | 2 |  251.32763671875
 2 | 3 | 220.749786376953
 2 | 4 | 147.224319458008
 2 | 5 |                 
 3 | 1 |                 
 3 | 2 | 220.749786376953
 3 | 3 | 180.312225341797
 3 | 4 | 67.7497863769531
 3 | 5 |                 
 4 | 1 |                 
 4 | 2 | 147.224319458008
 4 | 3 | 220.749786376953
 4 | 4 | 43.1210060119629
 4 | 5 |                 
 5 | 1 |                 
 5 | 2 |                 
 5 | 3 |                 
 5 | 4 |                 
 5 | 5 |                 
(25 rows)

The value for 4x3 is incorrect.

The equivalent in ArcGIS Spatial Analyst's Hillshade tool with azimuth = 315 degrees and altitude = 45 degrees on the attached raster (same as what is built in sql) looks like

NUL NUL NUL NUL NUL
NUL 251 220 147 NUL
NUL 220 180  67 NUL
NUL 147  67  43 NUL
NUL NUL NUL NUL NUL

The cell 4x3 should be 67, NOT 220.

[dustymugs]

source raster

[dustymugs]

ArcGIS's hillshade

[dustymugs]

World file appropriate for both tif files

[dustymugs]

ST_Hillshade in -trunk is also incorrect.

[dustymugs]

ArcGIS's slope

[dustymugs]

ArcGIS's aspect

[dustymugs]

For -trunk, better to use the following query

WITH foo AS (
	SELECT ST_SetValues(
		ST_AddBand(ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0), 1, '32BF', 0, -9999),
		1, 1, 1, ARRAY[
			[1, 1, 1, 1, 1],
			[1, 2, 2, 2, 1],
			[1, 2, 3, 2, 1],
			[1, 2, 2, 2, 1],
			[1, 1, 1, 1, 1]
		]::double precision[][]
	) AS rast
), bar AS (
	SELECT
		ST_Slope(rast, 1, '32BF') AS slope,
		ST_Aspect(rast, 1, '32BF') AS aspect,
		ST_Hillshade(rast, 1, '32BF', 315, 45) AS hillshade
	FROM foo
)
SELECT
	ST_DumpValues(slope)
FROM bar

[dustymugs]

Fixed in -trunk as of r10619

[dustymugs]

Fixed in 2.0 as of r10620

[dustymugs]

Oops. Forgot to resolve ticket.