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DTM, error code, runtime error, low memory

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What is the best way to get help? I have tried several post here and received some replies with suggestions. I have not been able to resolve my problem. I repeatedly get error code 20,2 and 20,1 and runtime errors when trying to use view options and settings. I have used the check polygon and filter polygon tools. When I try to use station on polyline for a road, I get the message that there is no intersection. I did resently upgrade to most current VW10.5. Would reverting back to VW 10.1 solve my problem.

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Here is some background information, maybe that will help solve my problem: My computer system: I have a Dell Pentium 4, 3.2 Ghz with 2G ram with Nvidia Quadro FX1000 w/128MB, dual monitors.

Project: 170 3D polygons, file size can range from 15MB to 60MB when and if a model is developed, Model approx. 10 acres, 120' change in elevation, 1/4 to 1/2 mile road w/several switchbacks, inset 40' x 60'garage into contour of the site. Am I asking the program or the computer to do more than its capabilities?

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  • Vectorworks, Inc Employee

Abrodin, I've reviewed your file. You have a detailed topo plant consisting of 170+ 3D polygons, each ranging from say 100 to 700 vertices -- let's say an average of 300 vertices. 300 x 170 = 51000 points. Generally, the DTM is designed to use much less dense data and create topo plans (which you already have in effect) and site models.

You're starting with a data set that has already been generated from a DTM from a much sparser set of data (I can tell from the triangulation of the site) and the extra data points are (trust me on this one) extraneous. They serve to do nothing but clog up the DTM engine.

To make calculation easier, you can do one or both of a couple of things:

1. Use major topo lines only and let the DTM interpolate the minor topo lines; and/or

2. Do an intelligent filtering of the 3D polys to reduce point density.

We provide a command for (2) called (appropriately enough) "Filter 3D polys". Try using it and setting your filter value to between 6" and one foot. I tried this with your data set using 6". I then created a site model from all data (major and minor lines) and got a model of about 6 MB in size in about a minute. Then I used (filtered) major contours only. The model calculated in about 5 seconds and produced a file that was about 600 kb in size. I suspect that either of the models would work just fine for the purpose you have.

So, what's the moral here? The idea is to understand both what your end goal is and to understand what you're starting with. The real purpose of the DTM is to taks relatively sparse data, interpolate it, and make topo and model data from it. You don't gain anything by making a DTM model from data that already been interpolated. But when that's the only data you have, you shouldn't feel bad about throwing some of that data away. (We are after all talking about dirt here).

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51000 points does not sound much to me so if the VW 10 DTM chokes on that, it is still useless. OK, it may be a lot for a single house site, but there are other types of projects... With filtering, I have spent endless hours in getting rid of intersecting polygons; when converting the 3D polys to 3D loci, the problem per se goes away, but of course produces wrong results. And boy, is it difficult to find these intersections, as there is a dialog for each and every one of them, reporting page-related coordinates!

Why can one buy a $200 DTM add-on to AutoCAD, one which works with hundreds of thousands of points, can use attribute data to generate the model (the standard way of getting terrain info from GIS systems), does slope analysis correctly etc etc, but one has to pay significantly more for the inferior (mostly useless) DTM capability in VW?

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The original survey data was imported from an autocad plot plan. Autocad had generated the topo lines. When I imported the .dwg file, the topo lines came as 3D symbols. I converted to groups and decomposed and recomposed and converted to 3D polys. I also had elevation points from the triangulated information. What would have been a better way to deal with the data and make a vectorworks model. The end result that I needed was a model of the area with the road and garage. The intent is to be able to manipulate the contours over the garage (the garage is inset into the hill with an IRMA roofing assembly) to find the best location with respect to the view and the house.

Fortunately I do have the training CD's for the Industry Series, and I did use the Landmark one prior to and during my attempt at the DTM. Prior to contacting the techboard for help the first few times I tried filtering the 3D polys, then check 3D polys and corrected any crossovers. I was unable to set the view options and settings (error code 20,2 and/or 20,1) Using the filtered 3D polys I created 3D loci with the same resulting error codes. I also used a much smaller area of the plot plan with limited success. I could get a model, but was unable to use the settings and view options (error codes 20,2 and 20,1). I also did several small tests: 5 3D polygons 200' long in 5'elevation increments, 6 vertices each. I again received the error code 20,2)

I did not find addressed how to use the site modifiers to inset the garage (a rectangular hole in the hill with contoured dirt on top). I will go through it again after I successfully create my DTM.

I successfully created a DTM using 3D loci at the triangulated points imported from autocad, 166 points. It doesn't have as much detail as I would like. What is an appropriate target range for the number of points in a data set? I want to be able to provide enough detail without chocking the DTM processor. I do have another data set from the plat of the area. I would like to use some additional points from that survey to fill in holes and details of the terrain. How many points is too many?

Thanks for your help!

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Originally posted by abrodin@alaska.net:

I successfully created a DTM using 3D loci at the triangulated points imported from autocad, 166 points. It doesn't have as much detail as I would like.

Considering how all DTM programs work (=TIN, triangulated irregular nodes), that 166 is likely to be all the actual, surveyed data there is and the level of detail cannot be increased. Everything between the points is done by interpolation; if you compare your contours with AutoCAD contours, they are likely to be identical, take or leave a few centimetres.

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Exactly how many points can VW 11 process to create a DTM? I know it depends on RAM, etc. but I have 1.3gigs of RAM on a high end DELL machine and I can't get the program to process 3000 loci. It just hangs forever. Man, if it can't do 3000 points there is something terribly wrong with this software. LandCAD chews through this many points in seconds. I had hoped that version 11 would have fixed this limitation.

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