Civil engineering feature implementation (Transportation Engineering)

[Pauvres_honteux]

Hi guys, anything in this topic you can utilize?

Acceleration or forces vs Bezier curves

[microelly2]

I've been playing around with the tool myself and looking at the code (you guys need to slow down lol, making me feel bad).

Don't look at me. This is entirely microelly's doing.

I wish o how I wish their was survey foot option in the preference file for working units.

Hmmm... so 1 survey foot = 1.000002 international feet. Or 2 * 10^-6 difference. Setting up a new unit of measurement for that shouldn't be an issue, but I wonder if floating point error might complicate that...?

Support for different units ca be added in a later step (after the algorithmic questions are answered), but we can already look at the impact of such a small change.

[olof]

I'm having some getting a sane mesh or point cloud from LIDAR data published by the Environment Agency in the UK. The point cloud created during the initial import looks good but when I try to create a new point cloud or mesh it is no longer sane. To me it looks like a possible scaling problem on the z axis.

lidar_xy.png (31.34 KiB) Viewed 1253 times

The point clouds when viewed from above look sane when viewed from the top

lidar_zx.png (10.46 KiB) Viewed 1253 times

However the z values are clearly incorrect when viewed from the front

I'm using the latest version of geodata, installed via the addon manager.

My freecad flie is at https://www.dropbox.com/s/2zfh3odr8x584 ... fcstd?dl=1 and the original LIDAR data at https://www.dropbox.com/s/5jxdrv6lm2rsw ... 6.laz?dl=1

Any thoughts?

My version info is:
OS: Ubuntu 17.10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.13509 (Git)
Build type: None
Branch: master
Hash: 0258808ccb6ba3bd5ea9312f79cd023f1a8671b7
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.1.0
Locale: English/UnitedKingdom (en_GB)

[microelly2]

May be we have to add an extra scaling factor for z in this case.
Can you post the lat/lon coodinates of your terrain, so I can compare it against other height sources to find the right factor.

[olof]

The location is 50.8041221,-2.278285 (https://www.google.co.uk/maps/@50.80412 ... 285,16.49z)

Thanks!

[Joel_graff]

Hi guys, anything in this topic you can utilize?

Acceleration or forces vs Bezier curves

Interesting. I've never really thought about roller coaster designs. With respect to roadway curvatures, whether highways or railroads, most of that is dictated by established policies. The point about centrifugal force (or is it centripetal? I never know...) is a significant one and it reminds me we need to explore that, too.

Specifically, in highways / railroads, we use the concept of superelevation, which is just banked curves like on a race track, but much less extreme. Of course, they're everywhere in a roller coaster. The rider comfort issue is usually managed using any of three factors: posting a speed limit, lengthening the curve, and/or banking / superelevating it.

Whether or not the spline comb will come in handy, I can't say. It might be useful for edge cases, but I think if we can get the spline to always be mathematically equivalent to a series of simple arcs and line segments, the managing the comb will never be an issue. There are exceptions, though.

[olof]

May be we have to add an extra scaling factor for z in this case.
Can you post the lat/lon coodinates of your terrain, so I can compare it against other height sources to find the right factor.

I've just found this about the EA LIDAR data (https://content.historicengland.org.uk/ ... r-data.pdf):

One important thing to bear in mind is that the data for the individual tiles captured by year has the height data in millimetres rather than the usual metres. This means that when importing into any program for viewing or creating visualisations it is necessary to rescale the vertical settings by 1/1000. If this is not done then any visualisation created will be so with a vertical exaggeration of 1000 times, something that can lead to excessive contrasts that hamper interpretation.

[microelly2]

You may hack into geodat/geodat/import_lidar near line 10
to get it running for your data

bp_761.png (8.62 KiB) Viewed 1192 times

[Joel_graff]

I will look at your model tomorrow.
for the moment I have the script to generate a Arc+Line+Arc Bezier.
bp_756.png
it's in my git, next I have to merge it and to start writing concepts.

I know you've been occupied on other fronts - I see you've been doing good work developing bezier to b-spline conversions...

Any chance you've looked more at our more constrained use case? I've pulled your code to my local machine and tested it (caught a missing import for regular expressions...)

[microelly2]

I'm still on the front:
I have learned about OpenInventor objects - we will need them to add illustration information (staging etc.) into the modesl.
So I worked on methods to display colored line sets.
https://forum.freecadweb.org/viewtopic. ... 30#p228778
This methods are very fast and will be used to replace the shape structures of the osm imports.

With the results of my experiments with Bezier curves I asks me can we create Sketches where the inner structure (geometry) is completly different from the shape. It is for example possible to create a real nonplanar 3D curve as Shape of a Sketch. We can work inside the sketch with lines and the shape displayes the arcs and lines.