[gdal-dev] dfMaxAngleStepSizeDegrees in ApproximateArcAngles

[Even Rouault]

I can't replicate that. Below the output with the Python bindings that 
directly map OGR_G_ApproximateArcAngles():

>>> from osgeo import ogr
 >>> g = ogr.ApproximateArcAngles(0, 0, 0, 1, 1, 0, 0, -90, 0)
 >>> g.FlattenTo2D()
 >>> g.ExportToWkt()
'LINESTRING (1 0,0.997668769190539 0.068242413364671,0.990685946036331 
0.136166649096247,0.979084087682323 0.203456013052634,0.962917287347799 
0.269796771157024,0.942260922118821 0.334879612170986,0.917211301505453 
0.398401089846241,0.887885218402375 0.460065037731152,0.854419404546489 
0.519583950035434,0.816969893010442 0.576680322114867,0.77571129070442 
0.631087944326053,0.730835964278124 0.682553143218654,0.682553143218654 
0.730835964278124,0.631087944326053 0.77571129070442,0.576680322114867 
0.816969893010442,0.519583950035434 0.854419404546489,0.460065037731152 
0.887885218402375,0.398401089846242 0.917211301505453,0.334879612170986 
0.942260922118821,0.269796771157024 0.962917287347799,0.203456013052634 
0.979084087682323,0.136166649096247 0.990685946036331,0.068242413364671 
0.997668769190539,0.0 1.0)'

>>> g = ogr.ApproximateArcAngles(0,  0, 0, 1, 1, 0, 0, -90, 10)
 >>> g.FlattenTo2D()
 >>> g.ExportToWkt()
'LINESTRING (1 0,0.984807753012208 0.17364817766693,0.939692620785908 
0.342020143325669,0.866025403784439 0.5,0.766044443118978 
0.642787609686539,0.642787609686539 0.766044443118978,0.5 
0.866025403784439,0.342020143325669 0.939692620785908,0.17364817766693 
0.984807753012208,0.0 1.0)'
 >>>

For the inc=0 case, note that there's a x/y inversion compared to your 
output.

The inc=10 case has 10 points in its output as expected

Even

Le 16/06/2022 à 18:27, Joaquim Manuel Freire Luís a écrit :
>
> Even, I wrapped OGR_G_ApproximateArcAngles() in Julia and I think 
> there is something wrong with the  dfMaxAngleStepSizeDegrees argument
>
> (here shortcut to ‘inc’)
>
> This is fine (just repeating the default 0.0 value). Note, I’m 
> dropping the z (=0) argin but that’s only the julia wrapper interface.
>
> D = GMT.Gdal.arcellipse(0, 0, 1., 1., 0., -90., inc=0.)
>
> BoundingBox: [6.123233995736766e-17, 1.0, 0.0, 1.0]
>
> 24×2 GMTdataset{Float64, 2}
>
> Row │ x            y
>
> │ Float64      Float64
>
> ─────┼────────────────────────
>
>    1 │ 6.12323e-17  1.0
>
>    2 │ 0.0682424 0.997669
>
>    3 │ 0.136167 0.990686
>
>    4 │ 0.203456 0.979084
>
>    5 │ 0.269797 0.962917
>
> ⋮│⋮⋮
>
>   20 │ 0.962917 0.269797
>
>   21 │ 0.979084 0.203456
>
>   22 │ 0.990686 0.136167
>
>   23 │ 0.997669 0.0682424
>
>   24 │ 1.0          0.0
>
> But if I use for example 10 (or any other number) the dfEndAngle is no 
> longer respected
>
> D = GMT.Gdal.arcellipse(0, 0., 1., 1., 0., -90., inc=10.)
>
> BoundingBox: [6.123233995736766e-17, 0.9993908270190958, 
> -0.17364817766693033, 1.0]
>
> 26×2 GMTdataset{Float64, 2}
>
> Row │ x            y
>
> │ Float64      Float64
>
> ─────┼─────────────────────────
>
>    1 │ 6.12323e-17   1.0
>
>    2 │ 0.0697565 0.997564
>
>    3 │ 0.139173 0.990268
>
>    4 │ 0.207912 0.978148
>
>    5 │ 0.275637 0.961262
>
>    6 │ 0.34202 0.939693
>
>    7 │ 0.406737 0.913545
>
>    8 │ 0.469472 0.882948
>
> ⋮│⋮⋮
>
>   19 │ 0.951057 0.309017
>
>   20 │ 0.970296 0.241922
>
>   21 │ 0.984808 0.173648
>
>   22 │ 0.994522 0.104528
>
>   23 │ 0.999391 0.0348995
>
>   24 │ 0.999391 -0.0348995
>
>   25 │ 0.994522 -0.104528
>
>   26 │ 0.984808 -0.173648
>
> Joaquim
>
>
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