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Linework simplification

Anonymous
Not applicable
I have some topography lines that I want to convert into a site mesh. The problem is that they are way too segmented. I tried using the linework consolidation tool, but what I would have drawn with a single line manually exists as a series of segments barely different in angle. Short of redrawing every contour line, does any one know of an existing method for simplifying this?

It would be nice if you could enter a minimum angle and then ArchiCAD would go through the polyline:
if (angle ABC is less or equal to the minimum angle)
then (delete segments AB and BC. add segment AC. repeat for AC and the next segment)
else (repeat for BC and next segment)

This would work well as an option in the linework consolidation tool.

pardon my pseudo-programming
18 REPLIES 18

Chazz
Contributor
Mr (or Ms.) Dmn, I agree that that deviation angle would be an effective and welcome option of the magic wand. There is a wiki article on this exact contour line problem and I would have even searched for the link if you had included a sig in your post --as is the custom 'round these parts. A name and a city is also appreciated by us curious folk.

welcome aboard.
Nattering nabob of negativism
2019 MBP

Thomas Holm
Booster
dmn wrote:
I have some topography lines that I want to convert into a site mesh. The problem is that they are way too segmented.
A number of tips on this subject:
http://archicad-talk.graphisoft.com/viewtopic.php?p=105587#105587
AC4.1-AC24SWE-25INT; OSX11.5; MP5,1+MBP16,1

Anonymous
Not applicable
Thomas wrote:
dmn wrote:
I have some topography lines that I want to convert into a site mesh. The problem is that they are way too segmented.
A number of tips on this subject:
http://archicad-talk.graphisoft.com/viewtopic.php?p=105587#105587
Thank you.

Anonymous
Not applicable
On second thought, it doesn't solve my problem. I thought the method in the ArchiCADwiki link would work, but if you're not careful, or if the terrain is complex, it results in overlapping lines. It really needs to be according to angle. So my request stands.

Anonymous
Not applicable
mmm, and if the script could also limit placing a new segment by detecting wether or not it's overlapping another segment (checking against the adjacent contours) that would be even better

Chazz
Contributor
dmn wrote:
mmm, and if the script could also limit placing a new segment by detecting wether or not it's overlapping another segment (checking against the adjacent contours) that would be even better
It could be that taking a completely different approach is the answer, nice though the angle segment tweak might be to the magic want tool. What about using Architerra. I haven't used it in ages but it seemed to be moving in the direction you would like.
Nattering nabob of negativism
2019 MBP

Dwight
Newcomer
Whenever the discussion of contour lines being difficult to manage or that contour lines create too many mesh nodes, I fell obliged to recommend a simplified method of terrain modeling that takes only a few minutes and speeds 3D imaging.

Contour lines are abstracted interpolations from samples. This data is converted into what is supposed to be a horizontal slice through a site. When we model a site, we seek to conform our model to the true shape of the site, but the contours are simple interpolations of this data and can't be totally accurate.

My method of site modeling is to create an adaptive grid. It is adaptive because the grids get smaller in steep or complex areas and larger in flatter areas. You place this grid over the site plan and add mesh nodes elevated to match the nearest contour height. Prominent outcroppings get higher detail.

This method creates a plausible site form with a fraction of the nodes, but in doing one, you must be aware of the general location of building areas.
If you do have an idea of the building plots, you can level these areas as you work.
Dwight Atkinson

TomWaltz
Newcomer
why not just turn down the resolution on your magic wand?
Tom Waltz

Thomas Holm
Booster
Dwight wrote:
My method of site modeling is to create an adaptive grid. It is adaptive because the grids get smaller in steep or complex areas and larger in flatter areas. You place this grid over the site plan and add mesh nodes elevated to match the nearest contour height. Prominent outcroppings get higher detail..
Dwight, could you please link to (or write a brief tutorial on how to do this? Or perhaps just an exampla of an adaptive grid in plan view?
AC4.1-AC24SWE-25INT; OSX11.5; MP5,1+MBP16,1

Dwight
Newcomer
To The Two Thomases:


You don't just turn doen the magic wand because it still doesn't guarantee a pattern. [Smack]

BTW: This is a total cheat.

Just put a grid on the site.

It takes some judgement to decide on the initial size, but this is a manual technique with future benefits that you learn from experimenting.

It is only applicable to situations when you aren't responsible for cut and fill calculations. You use this when you need a fast model and fast design views, since the objective is to reduce lag time with a small investment of labor.

Assuming a giant development site:
Start with 50mx50m. Look at the result. Assess the model for areas that could benefit from 25mx25m. By the time you do this, the general contour should appear smoothly. Find other areas - perhaps areas you'll be working in rather than background. 10mx10m. By now you should see something that not only follows the contours quite well, but has a regular pattern without illogical nodes. Any rectangle can only have two polygon triangles.....

IE: the simple magic wanding of contours leads to many bridging polygons that needlessly complicate a model without adding to information value.

After this degree of resolution, it is time to address feature details. Here, you can apply control lines to make ditches and add specific nodes to describe heffalump holes and outcrops essential to the design. You might also consider your building plots - don't add nodes in building footprints.
Dwight Atkinson

Anonymous
Not applicable
Dwight wrote:
My method of site modeling is to create an adaptive grid. It is adaptive because the grids get smaller in steep or complex areas and larger in flatter areas. You place this grid over the site plan and add mesh nodes elevated to match the nearest contour height. Prominent outcroppings get higher detail.

This method creates a plausible site form with a fraction of the nodes, but in doing one, you must be aware of the general location of building areas.
If you do have an idea of the building plots, you can level these areas as you work.
I've built all kinds of topo models before in another program, but that one could do your method automatically. I wouldn't mind putting up a wish for that. I have a time frame and a site size which would make doing that method manually unrealistic.

Dwight
Newcomer
You have been engaged in the assignment for four hours now and will still be saddled with an illogical and polygon laden model. My method is faster than it looks and pays dividends in 3D navigation speed and section generation time.
Dwight Atkinson

Thomas Holm
Booster
Thanks Dwight! I've added your method to the terrain model tip link collection.
AC4.1-AC24SWE-25INT; OSX11.5; MP5,1+MBP16,1

Anonymous
Not applicable
Dwight wrote:
You have been engaged in the assignment for four hours now and will still be saddled with an illogical and polygon laden model. My method is faster than it looks and pays dividends in 3D navigation speed and section generation time.
...and it would take 3 days to model what I'm modelling to a satisfactory level using your manual method. And I haven't started the assignment yet either/ what's your problem?

Dwight
Newcomer
Sorry. How big IS this model?
Dwight Atkinson

Anonymous
Not applicable
Around 1.5x2.5 miles of rolling topography (maybe 200 feet of elevation change), including a mountain ridge and a campus with a series of project sites. I've already set up a grid of mesh planes on separate layers (not to be confused with the adaptive grid that might be applied to them) to cut it into smaller chunks. I could see simplifying the mountain using some manual adaptive meshing but the campus needs to be fairly accurate.

Dwight
Newcomer
Have you investigated ArchiTerra for this?
Dwight Atkinson

TomWaltz
Newcomer
That sounds like a lot of back-and-forth for something that should be just a simple matter of magic-wanding existing contours.

On a large (over 2 square mile) site, the grid method would take way too long to build.
Tom Waltz

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