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Metric to Imperial


Devin Johnston
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Hi everyone, I recently purchased a library of models that were created using metric units, I need to import them into my scene that was created using imperial units. When I do this the model is roughly twice the size it should be and to make it worse these are pre-rigged cars so I can't just scale them down to the size they should be. I'm using the Madcar plug-in from R&D Group along with their iCars library and I'm looking for a way to fix this without having to re-rig all these cars.

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Thanks for that link I had high hopes it would work but it doesn't seem to work. If I don't get any feedback from R&D Group I'm just going to have to re-rig all the cars myself, kind of defeats the purpose of buying these models. I can't believe someone hasn't created a script for this kind of problem yet.

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I was hoping it would work too. In researching I saw you posted at 'their blog'. That was yesterday and still no repply? That's a bummer.

Well, I'll put in a call, "Calling all cars (madcars, icars)..."

May now help will come by; Hey Herbie, are you around?

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I know this is a long shot but maybe you could try with Rescale World Units from Utilities/More... menu. I don't know what is ratio between metric and imperial units, but you should type in right value depending on what you want to change - car models or rest of the scene.

You may NOT change the rigged character/s' units in such cases and the only option then available is rescale your scene to their units, most commonly its metres to inches - 3937% and so on...

This should work.

And, one more thing..... just relax mate, the world is not ending here (though we are in 2012).

Edited by umeshraut
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Its not only US or Autodesk, we in India too mainly work in feet n inches and there's no problem whatsoever, only some prefer metric. And since we are on it, a major percentage of the designing and drafting community still produces single line drawings and asks the 3D modeler to do the needful :)

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there's no problem whatsoever

 

I beg to differ. As a designer, I should be able to draw in metric or imperial as I choose and when I choose. Even using both systems at the same time if it works for me. That is impossible with AutoCAD.

 

Additionally, the North American construction industry suffers from another problem of construction materials available in two different formats due to the US's partial adoption of the metric system. This can lead to a multitude of difficulties including design, supply or construction errors.

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Hey, Devin!

I don't know how these models were made (if they were really metric or "something like it"), but you shouldn't have had problems merging them into an imperial system set scene. What normally happens is that people mess up the whole unit setup BEFORE starting to draft, and from here it just sounds like the cars were done the wrong way. Try this:

- open a car scene and let it use the scene's unit scale (no rescaling)

- check the Display Units -> they should be in metric. If not, then the model is probably the wrong size already

- check the System Units -> they should be set to 1 unit = 1 inch (or, as I prefer, 1 unit = 0,025 meter so you don't have to deal with fractions)

If the original file is set like that, than there should be no problem loading it into another scene, even though it's on Imperial. If it's not set like that, than it's the wrong size, hence the giant car.

What I see a lot (and does not work right in these situations): Display Unit set to Generic (people pretend to work in meters when they're in fact working as if 1 inch = 1 meter) and/or System Unit set to 1 unit = 1 meter (3ds max was made to work with inches, so everything you say to it will be "converted" into inches. If you set it as 1 unit = 1 inch = 0,025 meter, then you're working along with it, the same size).

Alright, this got a bit longer (and more confusing) than I thought. Let me know if this helps you (or not).

Cheers!

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I could have sworn that Max handles properly made models in Communist units being imported into a model in Normal units. What I don't get is, why do you get to work in Normal on 99% of projects but when you do a federal project they make you switch to Communist?

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Hey Ernest long time no see, yea the rigging is the problem it won't scale with the geometry. I've purchased AXYZ design models before that are pre-rigged in metric and I've been able to adjust them to the correct scale but with these cars nothing seems to be working. I'm just going to have to start over and rig all the cars myself, kind of defeats the purpose of buying the collection of pre-rigged cars but what else can I do.

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Have you tried linking the rigged car to a dummy then scaling the dummy? If there is more than one object to the car, then group everything (bones, car, wheels etc) then link the group to the dummy, so the dummy is the parent. Scale the dummy. Then all the bones should still see themselves as 100%.

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Seting the system unit scale to 1 unit = 1 cm IS wrong. Although it can be done, it will simply change the size of things when working cross units (your case). If the guys who made this cars had left the system units alone (1 unit = 1 inch), you would not have even noticed the scale difference.

But, the damage is done, anyway. :-(

One thing that might work would be trying to rescale the model before merging it into your scene, without changing the units. Have you tried that?

BTW, display units are important when working in metric. If you keep it "generic" and "pretend" you're working in meters, per say, you'll have serious problems with dynamics simulations and gi calcs (max will interpret your "meter" as being the same size as a unit, meaning it will be like working considering 1 meter = 1 inch). Really messed up.

 

Sent from my GT-P7500 using Tapatalk

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Seting the system unit scale to 1 unit = 1 cm IS wrong. Although it can be done, it will simply change the size of things when working cross units (your case). If the guys who made this cars had left the system units alone (1 unit = 1 inch), you would not have even noticed the scale difference.

But, the damage is done, anyway. :-(

One thing that might work would be trying to rescale the model before merging it into your scene, without changing the units. Have you tried that?

BTW, display units are important when working in metric. If you keep it "generic" and "pretend" you're working in meters, per say, you'll have serious problems with dynamics simulations and gi calcs (max will interpret your "meter" as being the same size as a unit, meaning it will be like working considering 1 meter = 1 inch). Really messed up.

 

Sent from my GT-P7500 using Tapatalk

 

Yes, maybe I should have clarified when I said 'display units doesnt do anything'. What I should have said is that changing display units has no impact on the scale something is imported/exported/built at. It does however, inform you of the world scale something is built at, ie; it translated the world unit to your favourite unit. So always use a unit, not generic. That unit should be obeyed, dont second guess it, there needs to be a compelling reason to work out-of-scale.

 

However, I dont think scaling before merging will work. When you 'scale' you are adjusting more than an objects size. Key data is scaling relatively, you are applying a percentage multiplier to a bunch of stuff, that stuff is built relative to other stuff (bones|keyframes|geometry etc) and they interpret the scaling in different ways, as you are seeing.

 

In most 3d apps you need to place the objects to be scaled (bones|keyframes|geometry etc) in a null or dummy object. You then scale the PARENT. What this does, is tell all the stuff to get bigger whilst retaining '100%' values. You are kind of scaling the world around the object to be smaller...(bend the word around the spoon an all that).

This is why you can scale an XRef bound to a dummy and not have any problems. The XRef is just looking at the dummy, not the world.

 

Another trick for scaling is to scale in the sub-object level. Then you are truly making an object smaller or bigger at the geometry level.

 

Another way of doing this is XForm scaling, but thats another post.

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