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Old 29th June 2007, 09:11 PM   #1
jeffmorris
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Default Drawing units

I think that the default drawing unit in AC3D is one meter on one default grid square. If I create a 3D model using a 3D CAD program and the drawing unit in that program is one inch. If I export the drawing to DXF file and import the drawing into AC3D, the 3D model would be very large. I know that one meter equals about 40 inches so how do I scale down the 3D model to correct size?
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Old 29th June 2007, 10:38 PM   #2
Dennis
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Default Re: Drawing units

Actually, the units in AC3D are completely arbitrary. 1 unit can represent any number (1 inch, 1 meter, 7 yards, 2.6 feet, etc).

If I have my facts straight, the 1 unit = 1 meter has its roots in physics simulation and game programming, where common physics routines were applied with the assumption that 1 unit = 1 meter.

However, in most 3D modeling, this is often a suggestion, but you should not feel bound to follow it in any way.

That being said, if you'd still like to rescale a model that's in a 1 unit = 1 inch scale to 1 unit = 1 meter, you'll have to scale down the model significantly.

1 inch = 0.025400050800101603 meters (which works out to just under 40 inches per meter, as you've mentioned).

So once you have your model imported in AC3D, perform a Select All. With everything selected, look to your left where the "Move to", "Size to", etc buttons are. Find the "Scale" fields, and enter the following number in all 3 fields:

2.5400050800101603

Then press "Scale". Your model will be reduced to the 1 unit = 1 meter number.

I would only do this if you absolutely had to, however. If you have fine details in your model, they may get scaled down to where scaling them up again will not give you the same precise placement of vertices. This is actually due to limitations of the way floating point numbers are handled, not an AC3D limitation. At any rate, I generally stay away from resizing/scaling a model unless it's absolutely necessary.

Hope that helps

Dennis
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