Author Topic: CHALLENGE: Block Elevations to Contours  (Read 1845 times)

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Atook

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CHALLENGE: Block Elevations to Contours
« on: October 12, 2021, 04:07:57 PM »
Hey swampers,
I posted earlier about assigning elevations to blocks based on contour lines. There were some good ideas, but unfortunately, I'm too busy to write the thing. So I thought I'd post it here, and opensource the result. I get the code I want, someone gets paid, future programmers get to use the result. A win for everybody, not to mention this could be fairly entertaining. I decided after the fact to include LISP code, so if this post needs to be moved somewhere different, an admin can do that.

PROBLEMS:
The first problem is isolating what objects to use for the elevation models, and where. if possible I'd like to avoid user interaction here, but it may be that the user needs to be prompted for some elevation layers or something. If the solution requires user interaction, your solution must include the interface to do so.

The second problem is interpolating elevation values from the elevation models and assigning those values to blocks. If the points fall within the bounds of the proposed grade, the elevation should be assigned from the proposed grade. If not, they should be assigned from the existing grade.

Challenge drawing files are here.

CODE:
The code has to be .NET C# or LISP. Try to comment it well. Do not post compiled code, I will not run it (and neither should anybody else). Include your username in a comment at the top of the file. All code posted will be public domain. One entry per user.

.NET: post a complete sln file I can open and compile in VS2019 I'll netload the compiled dll into vanilla AutoCAD 2021.

LISP: Post an uncompiled LISP file.

DRAWINGS AND CHALLENGE
QUALIFY.DWG: Create a command 'RACE'. It will prompt the user to select the layers/or objects for both the existing and proposed contours. Using those contours, calculate and set the elevations for the test blocks in Qualifer.dwg. All blocks should get an elevation within .25' of what I've got shown there (after all, my math could be wrong) Note that the base file in the xref is twisted about and not at 0,0 etc. Sometimes CAD monkeys do weird things, and we gotta accomodate that.

RACE.DWG: If your code qualifies, I'll run it 3 times on this drawing on my machine and average the times. I'll be using AutoCAD 2021 for the test. There is a single xref in this drawing that contains all the contours. Code that produces elevations that do not agree to consensus(within .25') with the rest of the entries will not be eligible for the prize. Include a timer in your project. Start the timer from when the user finishes selection of the layers. Print the elapsed time to the command line once the command is complete.

DEADLINE: October 22, 2021, 5pm MST.

PRIZES:
Paid in paypal, crypto, however I can get it to you.
Fastest .NET Solution: $400
Fastest LISP Solution $400
2nd Fastest (either): $100
Donation to Swamp: $200

If there's questions/clarifications needed, I'll do my best to clear them up before the deadline. I should have results the following week.

Good luck!
« Last Edit: October 13, 2021, 03:54:36 AM by Atook »

John Kaul (Se7en)

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Re: CHALLENGE: Block Elevations to Contours
« Reply #1 on: October 12, 2021, 04:38:42 PM »
Thank you very much for considering a donation to TheSwamp! Any donation, especially one this size, will help me keep this place open and running.

Good luck everyone.
TheSwamp.org (serving the CAD community since 2003)

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BIGAL

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Re: CHALLENGE: Block Elevations to Contours
« Reply #2 on: October 13, 2021, 12:27:50 AM »
I think your approach is wrong, yes you can use plines/lines with a Z elevation to make a TIN surface. Once you have a TIN you have a 3dface network of triangles. So the z can be calculated correctly for any point lying on a 3dface, not rocket science and it is out there as a freebie.

Ok over at Cadtutor triangulation by YMG, TriangV0.5.9.LSP may be helpful.

CIV3D has work out a Z for a point built in, includes using lines.

Now where is that point on 3dface code. https://forums.autodesk.com/t5/visual-lisp-autolisp-and-general/choose-point-on-3dface/td-p/1601829

Do I win ? Or did I just save you $$$$ will try to find time to code pt on 3dface as per link.

Ok if you look at help and look into the CAL functions you find this one ilp(p1,p2,p3,p4,p5) so p1 is xyz in plan z can be 0, p2 is the same xy but a dummy Z above the 3dface, p3,p4,p5 are the 3 points of the 3dface.

The other way is using UCS 3 points and the trans function to work out Z.
« Last Edit: October 13, 2021, 01:28:26 AM by BIGAL »
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VovKa

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Re: CHALLENGE: Block Elevations to Contours
« Reply #3 on: October 13, 2021, 11:14:44 AM »
Fastest LISP Solution
on my ancient pc it took half an hour to complete the RACE.dwg
i don't think LISP is a good choice (even on faster PC)

Atook

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Re: CHALLENGE: Block Elevations to Contours
« Reply #4 on: October 13, 2021, 11:52:52 AM »
Quote
on my ancient pc it took half an hour to complete the RACE.dwg
:wideeyed:

I wasn't sure what a dataset like that would take to process. I'm looking forward to finding out.

As far as LISP vs .NET goes I really have no idea. I do know that RJP's LISP code consistently runs circles around my .NET code.  :shifty:

Atook

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Re: CHALLENGE: Block Elevations to Contours
« Reply #5 on: October 13, 2021, 06:21:06 PM »
Quote from: BigAl
I think your approach is wrong..
:yes:

Yup, I'm almost positive my approach can be improved. That's the reason for the challenge. :)

To be clear: I know I'm out of my league here, if you see a better way to extract the data out of the drawings than I suggested, code it up and show us all.  If there's some special way of doing this that's more efficient and works in vanilla CAD, that's what I'm trying to find out. Maybe it's TIN surfaces, maybe it's the Buckminster transform dot multiplied across a unicorn matrix, I really don't know. I expect most/all of the entries will be more efficient than what I would do. Heck, I'm not even sure my math is right, that's why I'm giving a .25 fuzz factor on the elevation answers.

I'm looking forward to learning how the wizards in the community would do this.

BIGAL

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Re: CHALLENGE: Block Elevations to Contours
« Reply #6 on: October 14, 2021, 07:18:10 PM »
The dwgs provided look like they have come from say CIV3D or similar, so getting a TIN as well would make life so much easier. Using just contour lines is not really a good idea unless you convert to a TIN, again though not as good as original TIN.

This is a page from CIV3D help https://knowledge.autodesk.com/support/civil-3d/learn-explore/caas/CloudHelp/cloudhelp/2016/ENU/Civil3D-UserGuide/files/GUID-FDBDB4BD-86C1-4A01-9EC3-FEAEF7DF0A97-htm.html

Ok so (command "cal" "ilp(p1,p2,p3,p4,p5)") will return a point XYZ of intersection of 3dface, p3 p4 p5, with a line p1 p2, p1 would have say z = 0 and p2 z =10000.

So I would take a point do a ssget 3Dfaces around it using a range, dwg may have 10,000 triangles, so maybe get only 20 3dfaces, and do the ILP with no 3dfaces from you no code. Would be very fast as not looking at all 3dfaces .

Some test code but need your dwg with 3dfaces before I continue.


Code: [Select]
(defun c:test ( )
(while (setq p1 (getpoint "\npick point"))
(setq p2 (mapcar '+ p1 (list 0.0 0.0 10000.0)))
(setq 3d (entget (car (entsel "\npick 3dface"))))
(setq p3 (cdr (assoc 10 3d)))
(setq p4 (cdr (assoc 11 3d)))
(setq p5 (cdr (assoc 12 3d)))
(setq  zpt  (cal "ilp(p1,p2,p3,p4,p5)"))
(if (= zpt nil)
(princ "\nPoint not on 3dface")
(alert (strcat "\nPoint is X= " (rtos (car zpt) 2 3)  " Y= "  (rtos (cadr zpt) 2 3) " Z= " (rtos (caddr zpt) 2 3)))
)
(setq zpt nil)
)
(princ)
)
(c:test)
« Last Edit: October 14, 2021, 08:07:38 PM by BIGAL »
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Atook

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Re: CHALLENGE: Block Elevations to Contours
« Reply #7 on: October 14, 2021, 10:15:39 PM »
The dwgs provided look like they have come from say CIV3D or similar..

I'm looking to use this code in an app for vanilla AutoCAD/BricsCAD. I don't have Civil3D, but we get drawings like this all the time from clients. The app needs to work without Civil3D.

Atook

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Re: CHALLENGE: Block Elevations to Contours
« Reply #8 on: October 23, 2021, 12:51:31 PM »
Dang! No takers?

How could I have organized this to have more people interested? Suggestions welcome.

huiz

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Re: CHALLENGE: Block Elevations to Contours
« Reply #9 on: October 23, 2021, 05:36:07 PM »
Well, personally I don't understand the chalence. You want to have a function that takes two selection sets of contourlines but then you want that function also run on one set of contourlines.


Also the qualification of reading xrefs and ucs things, what do you actually want? Is that a complete application with just that functionality or rather code that handles a process? In the latter case it is better to focus on issues like how to handle breaklines, contours with curves, crossing contours, given or calculated boundaries, etc.


I do have some code available that creates a triangulation of a series of points and it is not that difficult to calculate the position of a point inside a triangle like Bigal also suggest. But I don't feel the urge to spent a lot of time to write all that other code :-)


But that is a personal feeling.
The conclusion is justified that the initialization of the development of critical subsystem optimizes the probability of success to the development of the technical behavior over a given period.

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Re: CHALLENGE: Block Elevations to Contours
« Reply #10 on: October 24, 2021, 09:36:01 PM »
Immediately disqualified for two reasons, its compiled, its C++, and it has limitations.

1, I had to hard code a command for each drawing, “Qualify” and “Race”. The drawings are way different in their structure, one has a nested xref, the other does not. So I didn’t bother.

2,  wont adjust block refs that don’t fall inside a triangle.

3, my TIN is pretty slow, I’ll try to improve this

4, I will share the source, but now it’s a hack and embarrassing 

5, it may crash and burn down your office
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Re: CHALLENGE: Block Elevations to Contours
« Reply #11 on: October 24, 2021, 09:37:00 PM »
Immediately disqualified for two reasons, its compiled, its C++, and it has limitations.

see! I can't even count
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Re: CHALLENGE: Block Elevations to Contours
« Reply #12 on: October 25, 2021, 01:51:21 AM »
this one is like wicked fast! changed to using this https://github.com/delfrrr/delaunator-cpp
I had to modify it to make it 3d.

Race went from 12 seconds to 0.249 seconds

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Re: CHALLENGE: Block Elevations to Contours
« Reply #13 on: October 25, 2021, 02:55:18 AM »
Here’s the source for inspiration.

Steps.
Collect points from polylines using the elevation as Z;
Transform the points by blocktransform of the xref;
Run Delaunay triangulation
If the block is inside of a triangle, convert the triangle to a AcDbSurface, then AcGeSurface, then getClosestPointTo AcGePointOnSurface using the block position
Move the block

Notes Selecting the blocks to move would be easier if they were on their own layer, so they can be moved all at once.
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Re: CHALLENGE: Block Elevations to Contours
« Reply #14 on: October 25, 2021, 03:51:46 AM »
the delaunator is really fast, here's the output for a quality check. couple weird spots so I don't know if its good enough for this challenge
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