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View Full Version : DXF conversion from Autocad into Lightwave



MiniFireDragon
10-13-2004, 03:03 PM
Ok, I been doing some checking out here and have some questions for either Newtek or you lightwave Gurus out there.

I have drawn a roadway intersection in autocad where 1 unit = 1 foot. Now, I took that DWG file and turned it into a DXF r12 format.

I opened Lightwave and used the Open Object and imported the DXF into Lightwave. I was surprised that it actually brought all my triangles in the correct way! It worked! Well sort of.

It seems that Lightwave assumes my drawing is in 1 unit = 1 meter. Thats a bad thing as now my drawing is huuuuugggeeeee. Or atleast with some poking around and taking rough measurements I found that I need to scale my drawing by .3099 to get it to proper scale, to convert meters to feet it needs to be scaled by .3049. Since it is only a .005 difference I am assuming that Lightwave is seeing my drawing and importing to meters.

My question is: How can I get it to see my DXF as Feet?

I tried setting the units in Lightwave to FEET and to INCHES but it always imports the drawing the same. Even setting it to METERS it set it wrong.

So I ask, can I change this assumption or did the AMERICAN company we know as NEWTEK set it to always default to METRIC (perhaps this code came from Newtek Europe?)?

gjjackson
10-14-2004, 09:31 AM
I suspect LW doesn't really care about scale, since everything is 'Camera' based. Since objects are viewed through a camera a scale is unimportant. It's easy to just scale layout and objects to appropriate relations.

MiniFireDragon
10-14-2004, 11:29 AM
No it is not as simple as rescaling in the object in lightwave. Let me give u an example. I am an accident reconstructionist. I go out and meaure the scene, take notes and what not. Then I come back to my office and layout the scene Autocad. After that I use Eaglepoint's Site Design and Surface modeler to build a 3d object.

For those that are not familiar with the software. Let me give u a taste of what it can do. I can take a series of lines and set elevations (even slopes) maybe draw in contour lines and then click a button and the object draws triangles over the entire site in a matter of seconds. This becomes a true 3d object, of which I can take into Lightwave (and thus far, no problems accept for scale!).

Now back to the issue. If you bring this object into Lightwave and scale it down, you need to be precise with the scale point. And with lightwave, that isn't all that easy, nor is checking that the object is to proper dimensions. As with court cases, if something is wrong it could destroy your evidence. The other thing is, if you ever need to import the model in different sections, for say striping or lighting, you need to apply the exact same scale in lightwave at the exact location or everything DOES NOT line up. I know, I have grumbled at this issue a few times.

Not to mention if you want to add additional object later in Autocad, you need to apply the same scale in lightwave. So, in order to make everything work like it should you need to prescale the Autocad drawing. All this can be a pain if it is months later and you don't remember what you did.

The next issue is the older versions of Lightwave would reset the Origing of the model to be in the center of the object. BBBBADDDD!! I haven't gotten to see if this is so with the newer version of Lightwave.

So in essence, every item in Lightwave needs to be what it is in real life, or u might have a 10' motorcycle and a 3' man. Not good.

Silkrooster
10-14-2004, 09:34 PM
I just check importing a dxf file in ver 8.0.1. And there still is no options for scaling on import. Thought you would like to know.
Silk

10-15-2004, 05:42 AM
I'm constantly importing from ACAD2003, if the ACAD drawing is all solids or surfaces I use 3DS out from ACAD, if its a 'line' drawing I use DXF - being aware that converting to DXF tends to be erratic position-wise if there are Xrefs.
Fortunately we've made it into the 20th century and beyond, and all our ACAD drawings are metric.They are however in mm so I always have to scale in LW by '0.1%'.
The auto rescaling when you open either in LW modeler is a bit arcane, so I just leave the default settings. We do work a lot with luddite Americans who are still in 'feet and inches' and we always re-scale drawings in ACAD - which is a high precision drawing application and is very good at it (when we have worked on stuff we usually have to re-scale it before we send it back, because the luddites can't cope even with the concept!).
So yes, it is perfectly possible to scale accurately in LW modeler. .30490 is probably the number to go for, but ACAD, I suspect, does it more accurately. I would always stick with the 'origin' from the ACAD drawings if there was any danger of needing to output back to ACAD.
:mad: That stuff about setting LW for metric or imperial units is purely about display information/auto conversion of information for luddites. LW is in meters like most of the rest of the world, and although you can work at any scale you like (when I started in LW way back (version 3?) I was working in 1000x real size (i.e. in mm instead of m) - but that does present problems when you are trying to set lens behaviour, and puts the default settings of the procedural textures well out of the ballpark!
:rolleyes: America, learn meters, teach them to your children, it will save them so much extra work in the future! :rolleyes:

MiniFireDragon
10-15-2004, 06:55 AM
<pulls up a plan of an intersection dated 1955> Oh look, feet. <pulls up a current interesction> Oh look Meters! :) Personally I don't care, but because there exists atleast 2 ways to measure, one shouldn't be limited to just one way of importing.

mattclary
10-15-2004, 07:28 AM
AutoCAD is unit agnostic. It really achieves it's scaling when you go to plot the drawing. The default unit in LightWave is meters, so it interprets AutoCAD units into it's default unit.

Believe it or not, this might give you some insight:

http://www.rhino3d.com/accuracy.htm


Simple answer, after import into Lightwave, scale it down.