Digital Terrain Model bogs down VW big time

[bc]

I have a polygonal shaped property about 1700 ft by 2000 ft with about 40 3D polys (at 5ft per poly difference in elevation) for the source data. This is for site planning for a multi-unit development.

I have created a site model and it appears to be correct.

The problem is that with the DTM in any file, VW bogs way down to the point where even merely selecting takes about 2 minutes.

I do have autosave on.

This is unworkable so I ask:

1. Is this too big for VW?

2. Or is this too big for VW with my relatively old machine specs (mid 2009)?

3. Is there anything that can be done to make this workable?

Thanks

Edited March 27, 2015 by bc

[CipesDesign]

bc, Did you run Simplify 3d Polys before creating the Site Model? Is the data a long way from 0,0 ?

[bc]

No and no.

I'll try simplifying and get back.

[bc]

Working on it now I am having some trouble getting past this (see attachment).

I run the command but no apparent simplification. The same value in window appears each time.

I DO think you're on to something though as there seems to be a trillion vertices....

I'll keep at it.

[CipesDesign]

bc, the Simplify command will place a Group of 3d Polys directly over (on top of) the existing polys. (I'd guess that there is more than one such Group in your file now). Easiest way to do it is to create new (blank) Design Layer and choose that layer in the Simplify Pulldown. Then go to that layer and Ungroup, and then Create Site Model.

Also, you can change the value in the dialog. Use trial and error until you get a) less vertices, and b) acceptable results (not too different from the original polys). If I am using 2ft contours I will generally choose 2-3ft for the spacing/interval.

[bc]

Well that seems to work.

I did specify the same layer I was on for placement but it didn't seem to place anything. Select all = the same number of polys.

Deleting one showed nothing bneneath.

Anyway a new layer worked as my smallest poly went from 2009 vertices to nine.

So now I'll check out the new model....

Thanks Peter.

BTW, I had a little trouble understanding the help in the dialog.

I thought they meant the closest distance horizontally (in plan) between two adjacent polys.

[CipesDesign]

bc, glad it seems to be helping. That's a drastic reduction (2009 to 9!!) and I'd bet that the Site Model is actually responsive now.

Regarding the dialog, and for others that need to know, the "simplification tolerance" refers to the distance between vertices in a poly. I like to push that number as high as possible, without much visual change to the resulting poly (from the original). I check this by looking at the new set (group) of polys placed over the top of the original polys.

[bc]

WOW.

I can work again.

Like instant response.

Thanks for setting me straight on this simplification thing Peter.

They need your language in the hint box.

They can run code but they can't hint

[CipesDesign]

Awesome! Happy to hear about your success!

[Rossford]

I was once told that there was a max of 35,000 points you could use on a site model. Don't know if that is still true.

One simple test is that each contour line probably ought to have in the "tens of points" and certainly no more than in the "hundreds of points" if it is a long one.

I set up three standard layers - 2D contours (for working freehand, 3D contours for when they are converted, and Simplify 3D contours to transfer once they are simplified.

I still have an old Vector bits plug in you could use to simplify the 2D polys, too, before conversion. Sometimes handy in sharing files across AutoCAD when working in 2D only. I actually opened that script, copied it, changed the parameters so I had a low, medium and high conversion tool with one click of the resource browser.

Usually the limits specified by the VW algorithm are pretty good, and don't cross, but they may in complicated topos. However, I had to recently reduce the setting where some really steep contours down to a river crossed with almost any simplification. If you simplify much more, sometimes you get those crossing contours.

Lastly, I think you can set how your 2D polys are smoothed in the VW preferences/settings. The higher the smooth factor, the more vertices.

[Rossford]

Related question while thinking about it, but I was also told you could crop any site model once into a sub area. Lets say you generally need 2 foot contours, but in small areas, may want 1 foot contours.

Is that still possible?

[CipesDesign]

Sort of. Before creation, add the additional 3d Polys. Or you can Edit the Site Model and add additional 3d Polys. Or you can use Site Modifiers (which can be created from open or closed polys) or Stake Objects.

The copping of a Site Model I believe refers to creating a boundary for it, called "Draw Site Border" in the Settings dialog...

[bc]

Well I'm pretty sure my DTM had WAY more than 30,000.

I did in fact use the smoother. I think when I got down to the adjacent vertices they were like 5/8" apart over like 2,000 ft for each poly.

Amazing to think now that it was manageable at all!