This seems to be a recurring issue for me lately. I've seen models that while extremely detailed in ADT, the geometry was no where near 0,0,0. "So what?" or "That's not practical!" some might say. Well, does it really matter? In short, YES!
If the geometry is not near 0,0,0, a number of things can happen that will drive you buggy, and make you want to hang yourself when you find out the answer as to why you're having problems.
The first thing you will notice if your geometry is a good distance away from 0,0,0 is that walls will start refusing to clean up at corners and intersections. It will happen randomly too, some will clean up - others won't. This really becomes evident when you are dealing with a site plan on a multi building site. Ideally, you would want to position the center of the site plan near 0,0,0. This really requires advance planning if your project (Including the site plan and all buildings on the site plan) is incorporated into one project in Project Navigator. Since all buildings in their individual xref's would need the same common 0,0,0 point, they most likely will be a distance from 0,0,0. If you find your buildings outer most components further than about 1,000 feet, you will need to change your approach. Instead of having a site plan with the constructs automatically referenced into the proper positions, you will need a separate file for the site plan to insert the xref's into. Then you will need to move around each building to its proper location. Doing this before you send backgrounds to consultants will save you a major headache.
The other reason becomes painfully apparent when rendering your scene in ADT or VIZ. If your scene is far away from 0,0,0, you will get linework that does not display correctly and does not render correctly. This typically happens without your noticing when you bring you buildings into a file created by your civil engineer which contains the terrain geometry for the site. Quite often the terrains are 1,000's of feet from 0,0,0. I saw one today that was approximately 100 MILES from 0,0,0. Yeah, that's going to cause problems. When you get that far away, the software has a hard time crunching the numbers when they are that large. If you want the linework to clean up and no longer have jagged edges along shadow lines, you will need to copy the geometry and paste it into a fresh, clean, new file. Simply moving it is not enough for some reason.
Hope this helps prevent a few headaches and hangings!
Monday, September 18, 2006
0,0,0 - Does my geometry need to be near it?
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