Intersections Again

Intersections Again - Mensajes

#1 Publicado: 18/7/2020 9:08:11
ianlh

ianlh

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Hi All,

Trying to work out a universal way of getting the length of intersecting lines, easy when lines are level, but not so (for me) others.

The image below shows a lifting lug, the angle of action can be 0 deg to 150 deg for example. I need to know the length of the lines from the red circle to the outline, individually, then I can see the shortest length, this must be for all angles, effectively tracing the intersection point through the angles. I know I can use Pythagoras, but was hoping to use something like GPC, but this works only for polygons?

lug1.JPG

Lug Horizontal.sm (26,94 KiB) descargado 1162 vez(es).
#2 Publicado: 18/7/2020 13:42:58
Fridel Selitsky

Fridel Selitsky

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Try a short circle code.
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frapuano 18/7/2020 16:52:00
#3 Publicado: 18/7/2020 19:09:52
Jean Giraud

Jean Giraud

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Anything helpful in there ?

Solve Circle Ellipse Strophoid NASA.sm (238,09 KiB) descargado 1238 vez(es).
#4 Publicado: 19/7/2020 6:39:06
ianlh

ianlh

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Hi Jean,

I will have a look, I'm sure I can use something.
Thanks
#5 Publicado: 20/7/2020 5:24:38
Fridel Selitsky

Fridel Selitsky

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ianlh, in your example it’s convenient to use the rotation matrix

Lug Horizontal1.sm (18,13 KiB) descargado 1172 vez(es).
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Alvaro 21/7/2020 13:49:00
#6 Publicado: 20/7/2020 8:34:13
Jean Giraud

Jean Giraud

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Whereas the system is built scalar wrt θ
make it more convenient local at graph display.

Lug Horizontal_2.sm (22,51 KiB) descargado 1197 vez(es).
#7 Publicado: 20/7/2020 13:46:20
Martin Kraska

Martin Kraska

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This provides the shortest distance from the segments of the polygon to the circle. However, the distance isn't really to the segment but to a line through the endpoints of the segment. There is no test if the normal to the line through c is between the vertices of the segment.

For the given geometry this works. For proof of strength this is only useful if a given force may act under any angle but the force doesn't depend on that angle.

Lug Horizontal_Kr.sm (31,23 KiB) descargado 1175 vez(es).
2020-07-20 18_32_25-Window.png
Technische Mechanik mit SMath Studio: https://link.springer.com/book/10.1007/978-3-658-50592-9
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Alvaro 21/7/2020 13:48:00, sergio 20/7/2020 14:10:00
#8 Publicado: 21/7/2020 2:25:44
Alvaro

Alvaro

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Wrote

Hi All,

Trying to work out a universal way of getting the length of intersecting lines, easy when lines are level, but not so (for me) others.
...



Hi. Your request it's about a complex computer graphic problem. This is a page for an undergraduated course: https://www.fing.edu.uy/inco/cursos/compgraf/

This paper have a pseudo code for solve partially your problem:

http://www.itseng.org/research/papers/topics/VLSI_Physical_Design_Automation/Physical_Verification/DRC/Geometric_Intersection_Problems/1979-Bentley.pdf

Hope that's helps.
Alvaro.
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frapuano 21/7/2020 7:03:00
#9 Publicado: 21/7/2020 2:44:11
Alvaro

Alvaro

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Wrote

ianlh, in your example it’s convenient to use the rotation matrix

Lug Horizontal1.sm (18,13 KiB) descargado 1172 vez(es).



Hi. This is what's actually do the Ber'f function:

Clipboard01.gif

But notice that for use matrix multiplication for translations you must to use homogeneous coords ( http://elopez.fime.uanl.mx/@materias/732/@Tema%203%20-%20Transformaciones%202D.pdf page 15)

Best regards.
Alvaro.
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frapuano 21/7/2020 7:04:00, Fridel Selitsky 21/7/2020 4:23:00
#10 Publicado: 21/7/2020 7:37:50
Fridel Selitsky

Fridel Selitsky

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Thank you, Razonar.Aapplying homogeneous coordinates helps automate the process.

Variant with homogeneous coordinates

Lug Horizontal3.sm (17,83 KiB) descargado 1192 vez(es).
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frapuano 21/7/2020 9:44:00, Alvaro 21/7/2020 13:48:00
#11 Publicado: 21/7/2020 14:15:57
Alvaro

Alvaro

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Wrote

...
Variant with homogeneous coordinates ...



Another variant.

Lug Horizontal4.sm (34,62 KiB) descargado 1205 vez(es).

Clipboard01.gif

Clipboard02.gif

Homogeneous coordinates are helpful in projective geometry and conics and quadrics. For instance, preserve the duality, because you can use line coordinates ( https://en.wikipedia.org/wiki/Line_coordinates ).

I try to modify for use that in https://en.smath.com/forum/yaf_postst17357_Conics.aspx but can't found a close end. This is my atemp for the dual of a conic, it's envelope:

Clipboard04.gif

Best regards.
Alvaro
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Fridel Selitsky 21/7/2020 15:25:00, frapuano 22/7/2020 8:29:00
#12 Publicado: 24/7/2020 9:27:21
Fridel Selitsky

Fridel Selitsky

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Rotate around an arbitrary axis in space


3d rotate.sm (21,39 KiB) descargado 1221 vez(es).
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frapuano 24/7/2020 15:05:00, Alvaro 25/7/2020 14:10:00
#13 Publicado: 27/7/2020 0:37:33
Alvaro

Alvaro

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Hi Ber. That's not science, that's art. Maybe you can find this book interesting: Modern Robotics.

At page 608 in the pdf, for example:

Clipboard01.gif

Clipboard02.gif

The notation isn't the best, but it can be converted to a general Rotations and translations for the forward kinematics of a robot.

Best regards.
Alvaro.
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Fridel Selitsky 27/7/2020 4:49:00, sergio 27/7/2020 4:57:00
#14 Publicado: 27/7/2020 5:31:15
Fridel Selitsky

Fridel Selitsky

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Hello Razonar. "Modern Robotics" book
sparked my big interest. Thank you for the link.
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