Mini-challenge

TIG · 2 May 2012, 21:24

@tig said:

I have yet another drawn solution... I can't fault it but then again...

that appears to work... instead of copying the line up by the thickness of the brace, i +rotated about the center of the original line 180d. then traced over everything to get my shape.

except, when i use the tape, with 0.000000 accuracy, i get 5.995197, instead of what should be 6" in my example.

copying the bottom line up 6" (2x the measurement i used for 1/2w) should yield better results, but then i'd guess that the top or bottom would be off. or the rotate tool is inherently inaccurate.
Move+Ctrl to copy the bottom long-side lines up to 'T' [as there are two lines, split by the width/2 perpendicular line...] moved up to the top of the right-hand post [T]...

TIG · 2 May 2012, 21:27

@unknownuser said:

A slight variation on TIG's
http://www.screenr.com/7VC8
Another working solution [I think!]... but it uses a script

Rich O Brien · 2 May 2012, 21:33

A script that should be a default tool

If only Google accepted sketchUcation's offer to buy Sketchp that time

TIG · 2 May 2012, 21:38

@unknownuser said:

A script that should be a default tool
If only Google had accepted SketchUcation's offer to buy Sketchup that time
I know... I know... but we are now all Trimblers-in-our-boots

pbacot · 2 May 2012, 23:01

@tig said:

I have yet another 'drawn' solution...
I can't fault it... but then again... you might...

Without doing a test, I don't see the logic that when you rotate the line back up, that point E hits the diagonal at any meaningful (or snappable) point. It can't be hitting the 'M' midpoint of the diagonal... therefore it isn't width/2 off the true axis of the board. In fact, isn't the angle created the same as measuring width/2 from M to the bottom edge?

TIG · 2 May 2012, 23:11

That's was the point... you snap it to M but E can never 'touch' it - but it will align... landing on the centerline.
BUT... you have me 'banged to rights' - it doesn't work as it's not an exact fit, so there is still a tolerance issue
Back to the drawing board...

TIG · 2 May 2012, 23:23

Driven

I think this a variation of the two-instance-rotation-with-mutual-snapping solution posted earlier today...

Can you elaborate...

So far, I think that is the only good way [along with Fredo's weird snap inferencing example] ???

driven · 2 May 2012, 23:23

been watching with no spare time...

my solution, two instances of square component, the second moved to top of target post and rotated 180º, then in edit mode rotated again from pivot point and snaped to first instances [also rotating] none pivot corner.

john

v6

driven · 2 May 2012, 23:38

Tig,
your most likely right, I haven't had a good look at all the 'solutions'
I'm working 18hr days at the moment and just had a quick shot at it, needed a play before sleep...
john

mac1 · 3 May 2012, 16:04

mini__mac2.skpHere is improved on solution I posted early and all dimension have been verified to SU 32 bit float accuracy against the close form solution I presented above.
Note I have been using some of the post dimension Jeff posted early of 96" post height, 65" spacing and 3.5 rail width.
No plugin is used.
I did use the technique I posted almost a year or so ago on the exact solution of sphere line intersection.

andybot · 3 May 2012, 16:13

@mac1 said:

[attachment=0:1pq9h5l0]mini__mac2.skp[/attachment:1pq9h5l0]Here is improved on solution I posted early and all dimension have been verified to SU 32 bit float accuracy against the close form solution I presented above.
Note I have been using some of the post dimension Jeff posted early of 96" post height, 65" spacing and 3.5 rail width.
No plugin is used.
I did use the technique I posted almost a year or so ago on the exact solution of sphere line intersection.

Hey Mac1 - what "sphere" are you using? It's not clear in your model what your steps are.

mac1 · 3 May 2012, 22:35

@andybot said:

@mac1 said:

[attachment=1:3b4i0fcr]mini__mac2.skp[/attachment:3b4i0fcr]Here is improved on solution I posted early and all dimension have been verified to SU 32 bit float accuracy against the close form solution I presented above.
Note I have been using some of the post dimension Jeff posted early of 96" post height, 65" spacing and 3.5 rail width.
No plugin is used.
I did use the technique I posted almost a year or so ago on the exact solution of sphere line intersection.

Hey Mac1 - what "sphere" are you using? It's not clear in your model what your steps are.

Sorry did not make my self clear enough for you. At the bottom right I show the intersect point, at the bottom left I show the center of the sphere. Since SU is a 3d program any time you talk about intersecting a rotated line with a target line it must be on a spherical basis. There was no intent to show a sphere but the math basis must consider that or you do not have a closed form solution. SO the directed line segment from the line rotation point ( aka center of sphere) to the intersection of the target line( used as ref for guide point) is the points one needs to get the angle of rotation and the intersect with the rail width to the left post. SO the intersect ( guide point ) at the target line, the two 3.5 inch spaced guide lines are all rotated to the top of the left post to establish the points needed to draw the 3.5 rail to the proper points. Here is a screen shot of the skip file I posted some time ago.
[attachment=0:3b4i0fcr]SPHERE LINE INTERSECT.jpg[/attachment:3b4i0fcr]

mac1 · 3 May 2012, 22:56

BTW you need ground truth to know if your model is correct.
I presented the closed form solution for the 2d case above. Here is the excel results to check my model'

Ecuadorian · 3 May 2012, 23:01

The fact that this thread is already 19 pages long has made me seriously consider learning either MoI or Rhino.

andybot · 3 May 2012, 23:11

@mac1 said:

BTW you need ground truth to know if your model is correct.

Clear as mud

You still don't show your steps. I'd love to see the "sphere" you are using, or are you just talking about calculating and not modeling. Sure, anyone understanding basic trig can calculate the length of the edge based on the diagonal, that's been done a few times in this thread, but entering numbers seems to still end up with rounding errors in SU...

pilou · 3 May 2012, 23:11

Take Moi : It's the SU of Nurbs against Rhino !
Less powerful functions but it's not the same spirite!

I don't abort to find a more easy answer at this damned problem of align rotation who fail at mini micro sub-atomic snaping!

Charlie__V · 4 May 2012, 02:09

Greetings all,

A few months back I had a similar conundrum..........after fussing a bit I just "eyeballed it" to get my cross bracing.

"Knowing" the challenge, I have taken another swing at it...........though it still does not "zero out".

In short.........center the cross brace and scale it's "ends" to meet the vertical(s).

Sorry..........I do not possess video skills.

Best,

SKP_V8

SKP_V6

mac1 · 4 May 2012, 04:51

@andybot said:

@mac1 said:

BTW you need ground truth to know if your model is correct.

Clear as mud

You still don't show your steps. I'd love to see the "sphere" you are using, or are you just talking about calculating and not modeling. Sure, anyone understanding basic trig can calculate the length of the edge based on the diagonal, that's been done a few times in this thread, but entering numbers seems to still end up with rounding errors in SU...

I guess the best I can suggest is to use your imagination. I am sure you understand a line rotated around a point through 4 PI steradians makes a sphere. Since this is really 2 d problem the sphere degenerates to a circle. I did not calculate the lengths nor rotation and have not seen anyone present a closed form solution to that.I have seen some claims but will re-look since you assert they did post. I presented a closed form solution and since edges,angles and intersect points are not known math solution is not what you assert. The ground truth which was calculated was only done to validate the model approach. That means any different answer is either a model error or a SU limitation. The model results I presented are validated by the ground truth( calculated) ( With in of course SUs 32 bit float or really 24 bits( 1 bit for sign and 8 for exponent are used leaving 23 but using the sign bit makes 24 bits or 7 digits.) Accuracy for the rotation angle ,because of how SU truncates the number of digits reported, I did not validate.
All the info you need has been presented. I suggest you look at all my post just not the last one.The key to the model is finding the intersect point shown which was a subject of my post maybe 2 years ago. The approach is shown in the jpg posted above.
You are allowing yourself to get stove piped by looking for a sphere.
The steps are finding an intersect point and one rotation as shown.

jeff hammond · 4 May 2012, 06:02

.

is there a way you can dumb it down for us plebs?
i've never even heard the word steradian before (and if i have, it definitely never stuck )

i can't tell if you're showing a solution or.. what..

jeff hammond · 4 May 2012, 06:16

@unknownuser said:

Take Moi : It's the SU of Nurbs against Rhino !
Less powerful functions but it's not the same spirite!

Moi also makes it easier to stay in perspective viewport.. it has really nice inferencing and navigation..
michael just hooked up copy/paste between moi&rhino on mac so i think i'll be spending more of my time in moi now and just pasting into rhino if i need something more robust for a particular scenario..

@unknownuser said:

I don't abort to find a more easy answer at this damned problem of align rotation who fail at mini micro sub-atomic snaping!

lol.. i've tried so many things over the past few days to no avail.. i think i'm done trying..
i'll just wait a year or two when this thread is randomly rejuvenated with someone showing an incredibly simple way of doing this