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Summary 0025961: Wrong result of projection point on the ellipse
Revision 2015-03-20 11:30 by nbv
Steps To Reproduce Draw[]> ellipse ce 15793.1884865181, -5613.90386522167, -2450 0.566529531797242, 0.824041436823172, 4.04832179340053e-023 249106758.909924, 18
Draw[]> dset x1 15810.404909670384
Draw[]> dset y1 -5625.7401757733878
Draw[]> dset z1 -2468.0000000000000

Draw[]> proj ce x1 y1 z1
# parameter 1 = 3.141592653589798
#ext_1 parameter 2 = 4.7123890642550172
#ext_2 parameter 3 = 6.2831853071795809
#ext_3 parameter 4 = 6.2831853071795809
#ext_4

Draw[]> length ext_1
The length ext_1 is 249106779.80259019
Draw[]> length ext_2
The length ext_2 is 36.000000000000043
Draw[]> length ext_3
The length ext_3 is 249106738.01725906
Draw[]> length ext_4
The length ext_4 is 249106738.01725906

I.e. minimal distance between ellipse and point is 36.000000000000043.

However, try the following script:
Draw[]> cval ce pi/2 xx yy zz

Draw[]> dset sd (xx-x1)*(xx-x1)+(yy-y1)*(yy-y1)+(zz-z1)*(zz-z1)
# 436.50347299786017
Draw[]> dval sqrt(sd)
# 20.892665531182473

Consequently, there is a point nearer to the given with distance 20.892665531182473.
Revision 2015-03-20 11:29 by nbv
Steps To Reproduce Draw[]> ellipse ce 15793.1884865181, -5613.90386522167, -2450 0.566529531797242, 0.824041436823172, 4.04832179340053e-023 249106758.909924, 18
Draw[]> dset x1 15810.404909670384
Draw[]> dset y1 -5625.7401757733878
Draw[]> dset z1 -2468.0000000000000

Draw[]> proj ce x1 y1 z1
# parameter 1 = 3.141592653589798
#ext_1 parameter 2 = 4.7123890642550172
#ext_2 parameter 3 = 6.2831853071795809
#ext_3 parameter 4 = 6.2831853071795809
#ext_4

Draw[]> length ext_1
The length ext_1 is 249106779.80259019
Draw[]> length ext_2
The length ext_2 is 36.000000000000043
Draw[]> length ext_3
The length ext_3 is 249106738.01725906
Draw[]> length ext_4
The length ext_4 is 249106738.01725906

I.e. minimal distance between ellipse and point is 36.000000000000043.

However, try the following script:
Draw[]> cval ce pi/2 xx yy zz

Draw[]> dset sd (xx-x1)*(xx-x1)+(yy-y1)*(yy-y1)+(zz-z1)*(zz-z1)
0000436.50347299786017
Draw[]> dval sqrt(sd)
0000020.892665531182473

Consequently, there is a point nearer to the given with distance 20.892665531182473.


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