Terrain Modeling

[Anonymous]

I have created a terrain model (2.4MB) of ~3/4 acre (3432 m2). The computer now acts quite sluggishly and when I attempt to view the model in 3D, the beach ball appears, the program hangs and I must force quit (Mac) ArchiCAD in order to resume. (I've attempted to attach the 3D settings dialog box, not having done this before).

[Anonymous]

This is not likely due to your 3D settings.

It is probable that your mesh is either too complex for your hardware or that it is geometrically flawed and the machine is hanging up on the errors. Since the program hangs I would suspect the latter, but a G5 is getting to be a bit of an old machine to be running ArchiCAD so that could be part of the problem as well.

[Anonymous]

After importing the surveyor's topo and boundary file, I noticed that not all contours reached the boundary limits. Since the contour lines are polylines, I added to them in order to extend them to the boundary lines and treated them as contours. Is this appropriate? Prior to posting I was considering starting over in the event that there was an error on my part. But of course I don't know what that could be. The site has a 32' rise and it took a good deal of time to magic wand the contours (almost all in the surveyor's drawing were broken in order to insert elevation values). And then to assign elevation values. The further I went along the slower the computer performed. Could the fact that the surveyor's lines were not continuous be a problem? I did not join them with another line. And I assigned the same elevation values to the isolines either side of the break. Also, as I went along I would look at the progress of the model, and after about eight feet of rise it would take few minutes to reveal an image. I then changed the 3D settings to hidden line to see if that would make a difference, and finally to wireframe to no avail.

[Dwight]

You can reduce the number of nodes by imposing a grid over the site and interpolating the elevation at each grid point.

I recommend an adaptive grid: 50x50 for gentle slopes and as small as 5x5 for steeper slopes.

[Anonymous]

"Dwight" wrote:
You can reduce the number of nodes by imposing a grid over the site and interpolating the elevation at each grid point.

May I eliminate nodes along the contours given by the surveyor?

What I am understanding from your suggestion is to overlay the survey with the, say, 5x5 grid and produce new polylines over the top of the grid following the survey lines, in effect creating a new topo. Is this correct?

[Dwight]

Without descending into a diatribe about how we are all fools for emulating interpolated contour lines as gospel when describing a site, an adaptive approach leads to fewer, more easily imaged nodes.

Yes, you overlay a large grid on the site plan. Say, 50x50. Then you create mesh nodes at the grid intersections corresponding to your interpolation of the elevation based in adjacent contour line heights. [Of course, I have no way of knowing how big your site is - you may be able to go up to 100x100 or larger]

All you make are nodes, not polylines.

Where the slope is more critical, within each large grid, add a finer grid of nodes to describe outcroppings or creeks. Focus nodes where it counts, around the building plot, etc.

This makes a smoother, more realistic site.

[Anonymous]

While Dwight's method can be great for simplifying the mesh and making better renderings, I usually use the contour method because it is fast and displaying the contour lines in 3D and elevation views is often desirable.

I generally avoid using the magic wand on the DWG from the surveyor as this often results in site models that are way too complex. I prefer to trace the contours with the spline tool and then control the complexity with the magic wand settings.

In any case it still seems that your problem is with the complexity of or errors in the mesh. Whichever method you prefer to make the mesh it looks like you should start over and focus on keeping it simple.

You should also consider replacing your hardware. The PowerPC is no longer supported by either the MacOS or ArchiCAD and what you have there is getting very long in the tooth.

[Anonymous]

Thanks for the help, guys. Matthew, I have been considering a computer upgrade. Presently only my laptop can run 13. A top of the line 27" iMac looks interesting.