3d terrain from contour map  1-20  21-40  41

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 From:  steve (STEEVE)
2321.1 
This is an old and tricky problem. Would love to see what MoI-sters can do with it.

It starts with a contour map in vector format. Import into MoI. Set the contour lines to their correct heights.

Then the fun begins. I've tried various ways to create a surface from these objects, with not great success.

Any ideas?

Of course there are many ways to approach this problem, but it would be great to have a MoI solution!
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 From:  Michael Gibson
2321.2 In reply to 2321.1 
Hi Steve - I think that will probably need a kind of specialized terrain fitting tool which MoI does not currently have.

Probably the "Patch" command in Rhino is the closest thing I can think of to kind of process something like that more automatically.

One thing you can do in MoI to make some progress is to close each outline with line segments, then you can do some extrusions and booleans to make a solid like this (model attached as contour test2_3dm.zip):




Now with it as a solid shape, there are maybe some other possible steps you could do, like take some lines underneath it and project them up:





That now gives you a set of parallel sections, you can use each one as a guide to snap on to when drawing a smooth curve, and then loft the resulting smooth sections into a surface...

But you'll probably generally have an easier time if you use a tool that has some special things in it for terrain, MoI just does not have anything specialized for that currently.

- Michael

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 From:  jbshorty
2321.3 In reply to 2321.1 
I think it's out of MoI's reach to do this with any degree of accuracy. Ground has arbitrary topology and so it's best to use a mesh. Would need some tool like Rhino's Delauney triangulation described here:

http://en.wiki.mcneel.com/default.aspx/McNeel/PointsetReconstruction.html

Or in Moi - I suppose you could try making a series of cross-sections through those topo curves, and loft them to a surface. OR loft portions of the original curves until you've got individual surfaces making the hills and valleys, then trim them and join to a polysurface. But I think either method would be a very inaccurate... Another option would be a patch surface with a LOT of control points, or possibly use a mesh patch. But neither option are available in MoI...

jonah
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 From:  Grendel
2321.4 
If you had an aerial greyscale or topology map you could use Zsurf.
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 From:  Michael Gibson
2321.5 In reply to 2321.3 
I gaving patching this one a try in Rhino and it doesn't really do a very good job of this case neither, it is hard to handle that kind of steep gorge running through the middle with a fitting process. Maybe with a really gigantic number of points...

I think you may have something like a cliff or steep valley in this terrain plot? Probably that is going to need to be constructed in sections I guess to preserve a sharp drop, a fitting mechanism that wants to make a completely smooth thing won't handle an intentional sharp cliff very well.

Probably something specialized for civil engineering and TIN terrain models would be best.

Another kind of approach might be to take those outlines into a bitmap program nd make different shades of gray for the levels and do some blending and softening between them. Then you can take that into ZSurf to make a heightfield:
http://moi3d.com/forum/index.php?webtag=MOI&msg=602.7

- Michael
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 From:  Brian (BWTR)
2321.6 In reply to 2321.5 
Guess this is not helpfull---

Doing this sort of thing in Carrara, especially with the DCG "Ground Control" plugin, is just so easy. (All the free radar space maps of where YOU live!!)

I would never put it into the realm of a need within MoI myself.

Brian
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 From:  Frenchy Pilou (PILOU)
2321.7 
Export your 3dm in skp format from Moi
and free Google Sketchup gives you this with the Sand Box "from contours"
Is this like your original ?

EDITED: 13 Jan 2009 by PILOU

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 From:  BurrMan
2321.8 In reply to 2321.7 
Where are the releif lines coming from? The last time they were smooth curves. This time all "Corner Points".

Harder to get smooth surface from corner points.
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 From:  BurrMan
2321.9 In reply to 2321.7 
Looks like it made the lines the "Peaks" with "Valleys" between them.
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 From:  Frenchy Pilou (PILOU)
2321.10 In reply to 2321.9 
I just taken the original 3dm ! Nothing was made inside Moi except the export format SKP!
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 From:  Michael Gibson
2321.11 In reply to 2321.10 
Hi Pilou, I don't believe that your method generated proper results...

For example this curve is the highest one, and I think the way these topo lines work, that is supposed to be a plateau there:



However, your version appears to have made it a ridge that drops off quickly to the bottom level, rather than a plateau.

I don't know if you need to adjust the curves by closing each of them, or if the tool you are using is not the right tool for this kind of situation... Or maybe I don't understand what the proper result is supposed to be..

- Michael

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 From:  Frenchy Pilou (PILOU)
2321.12 In reply to 2321.11 
I made nothing! Moi was just used as "go between" with the 3Dm file given at the first post!
it's only automatic process by Google Sketchup!
Is for that I write :)
< Is this like your original ?
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 From:  Michael Gibson
2321.13 In reply to 2321.12 
Hi Pilou - yes I understand it was an automatic process, I'm just talking about the result - that does not seem to be the proper result as far as I can tell anyway!

Maybe closing the lines would help the automatic process that you are using to do a better job (and then probably do not give it the full bottom rectangle), or possibly the automatic tool that you are using is meant for some other task than this kind of a job, I'm not really sure.

- Michael
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 From:  Frenchy Pilou (PILOU)
2321.14 
Maybe the original must be hown because some variations can be existe !
Here I close some lines by hand inside Moi but without original some confusion exist :)
There is a point on the middle rectangle so...
The right corner can be like this or other...
etc

EDITED: 13 Jan 2009 by PILOU

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 From:  steve (STEEVE)
2321.15 
Thanks for the input everyone. It's a challenging problem.

Pilou, I like your solution! Actually I had forgtotten the sandbox tools. The reason why it produced strange results the first time (as Michael said) was because of the boundary rectangle at "z=0". Remove the rectangle and SU produces a pretty good result.

The idea of producing a DEM is also a good way to go. There's a neat app called Blackart which does this quite well. Grendel, thanks, I'll check out Zsurf. A 3d surface can also be made by applying the heightmap as a displacement map (blender, etc)

Generally the contours come from pixel images. Can be cleaned up a little (Gimp, etc), vectorised (Blackart or wintopo, etc) and saved as pdf, which MoI imports sweetly. Then join all contours, fix holes, get the scale right, elevate contours to correct heights.

Michael, the extrusion method is quick and could be useful sometimes. I wouldn't be surprised if the resulting mesh could be smoothed in some other app (Blender, maybe)

Anyhoo, it looks like whichever way it's done, it's gonna take time!

Steve
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 From:  Brian (BWTR)
2321.16 In reply to 2321.15 
A DEM Satelite Radar file brought into Carrara (.obj file)and detailed as an Vertex obj.

Brian

ps AND think of what can be done to it with the Carrara Displacement Painting, OR even more so, with the combined 3Dpaint/3D Displacement paint of 3D Coat!

EDITED: 13 Jan 2009 by BWTR

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 From:  steve (STEEVE)
2321.17 In reply to 2321.16 
Looks very good Brian. Are these satellite radar images generally available?

One of the problems would be with resolution. Generally I need to model a very small patch of earth's surface (50m x 50m max), with contours at 1/2m or 1m intervals...it's unlikely that such data will be easily available to ordinary folks any time soon!

What we really need is a hand-held combined GPS/altimeter. Wallk (or drive) over the land pushing a button every now and then. Come home, plug the data-logger into the computer and there is the terrain map!
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 From:  Brian (BWTR)
2321.18 In reply to 2321.17 
http://edc2.usgs.gov/geodata/index.php

No secrets in the world--these sources also allow you to place the water level for seas and rivers (For the imaging texture files) appropriatly.

And, to a limted extent in Carrara at least, you can approximate the "real" heigh of various levels.

Quite staggering to an old bloke like me!

I think you CAN do your last paragraph stuff--NOW!
Todays farmers use it regularly!

Brian
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 From:  BurrMan
2321.19 In reply to 2321.18 
Carrara handles SDTS files perfectly. Only not all area has coverage for free.

I think it does dems still also. Definatly Bryce still does dems. You have to get good at searching though as the usgs makes it next to impossible to find the free ones so you buy their pro sets. The EDU site all have links but finding them are hard. What you need is to find a student that already knows what the link is and PRESTO. Free Dems.
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 From:  steve (STEEVE)
2321.20 In reply to 2321.19 
I think all this is true for the US...for remote countries the data may not be so easily available.

I'm thinking that for a small piece of land without too many contours, a more "low-tech" approach may also work: trace the contours in MoI from a background image and use loft or network. It should be possible to get a decent result like that.

Michael, is there any possibility to convert a polyline to a nurbs curve?
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