The problem I am having is with merging objects. I have a car modelled in inches in system scale. It works fine when I merge it in architectural scale, ie. inches, but when I merge in file with meters as system scale, the objects come too small and scattered. Sometimes with other files, the merged objects come too small, but the objects are not scattered, that way I can scale it up, but it is still a rough scaling.
Why is the model built exactly to scale don’t come in scale in other system scale???, and why are the objects scattered like that? The display unit scale worked good, a 10ft cube shows 3.048m cube when I turn to meters, which I can understand. The same cube shows 120m when I then turn system scale from 1inch to 1meters which I worked out as 3.048*100/2.54, but am not really getting what dat means :D. Anyways, will love to get answers soon.

3ds Max 2009 64-bit
Core2 Quad @ 2.4GHz, GeForce 9500GT, 4 GB RAM, Win XP 64-bit
Kathmandu, Nepal

Are you merging or importing??  Merging assumes you are accessing a .Max file and bringing in some or all of the objects.  Importing involves file types other than .Max, where there may or may not be proper units.

Some files just have a generic unit type.  I run into these in our 3D library, when importing old .3ds files from years ago.  So when imported into a scene with Inches as the System Units, it looks correct.  But if imported into a file in Meters, the model is way too big.

3DS Max Design 2011 64-bit - Advantage Pack
Dell Precision T5500, Dual Six Core Xeon X5650 @ 2.67GHz, nVidia Quadro 5000, 24 GB RAM, Win 7 Enterprise 64-bit
Minneapolis, MN, USA

Hmm, I am importing(merging) .max files, the 3ds and other formats like dwg work better actually, because there is a dialogue to acertain the units and other stuffs. While merging there is no menu or sth to change the units of the merged objects. When the units match, I can just drag and drop into my max file and don’t have to worry about the scale. How can I do the same when units don’t match? Do I have to make a separate copy with the units changed, and even that how much to scale??? say if I changed from inches system units to meters and vice versa.

3ds Max 2009 64-bit
Core2 Quad @ 2.4GHz, GeForce 9500GT, 4 GB RAM, Win XP 64-bit
Kathmandu, Nepal

Merging from another Max file should just work without any intervention.

Open Max, change the System Units to Feet, change the Display Units to “Generic” (this is to remove a level of complexity).
Create a 1*1*1 cube. Name it “1 Foot Cube” - save the scene as “MergeFile.max”.

Reset Max, set the System Units to Inches and Display Units to Generic.
Create a 12*12*12 cube and name it “12 Inch Cube”.

Merge the “1 Foot Cube” from “MergeFile.max”. Lo and behold, they are the same size - prove this by using the Measure Utility - both are 12*12*12.

The problem you are seeing is more than likely because you are you are looking at the size of the object in the “MergeFile” distorted by the Display Units. You are then merging into a scene with different units also distorted by the Display Units.
To put it another way, in a scene with System Units of Feet but Display Units of Inches, you could create a 12*12*12 Inch cube, but it is really a 1*1*1 Foot cube.

This gets even more confusing when you start mixing Metric and Imperial measurements - having System Units Imperial and Display Units Metric is a real headache - avoid doing it if at all possible.

Once you work out the true size of of the incoming object it should be relatively easy to work out by how much that object needs scaling. However, you should NOT use the Scale Tool to do this - use the Rescale World Units utility.
Command Panel | Utilities (tab) | More.

Max 4.2 through 2013.
XP-64 (SP2)
NVidia 9800GTX-512 (Driver 266.58).
Core 2 Quad Q6600 2.4GHz, 8Gb Ram, DX9.0c.

Please see it for yourself, I want to put the things in mercedes file to the road file. I tried your example, they turned out okey, must be problem with my settings or something.

3ds Max 2009 64-bit
Core2 Quad @ 2.4GHz, GeForce 9500GT, 4 GB RAM, Win XP 64-bit
Kathmandu, Nepal

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There is something really wrong with that scene/model (the car). I can’t get it to merge, at the correct size, into any scene which does not have SU of Inches. That is just plain wrong. They seem to have some “baked in” scaling which I can’t remove easily. I did manage it by the following method - messy though it is.

On a copy of the car scene.
Unlink and then delete the 2 dummies.

For each of the 3 component parts of the car:-
Create a small box (size is irrelevant) off to the side.
Convert it to editable Mesh. Attach one of the car components.
Element SO level, Select the “box” element and delete it.
Hierarchy Panel, Affect Pivot Only, move it to [0,0,0].

You will need to rename them and re-apply the materials.
You can re-create the dummies if you want them - but do NOT scale them - if you use a Point helper set to Box you can adjust the size of it later if you need to. Link the components to the Dummy (or dummies).

Save the new scene. Load the “Road”, merge in the car from the new scene.

Max 4.2 through 2013.
XP-64 (SP2)
NVidia 9800GTX-512 (Driver 266.58).
Core 2 Quad Q6600 2.4GHz, 8Gb Ram, DX9.0c.

I agree with Steve, there is something weird going on with the car.  One thing that threw me off, too, was I unlinked the geometry from the dummies, then collapsed the objects into one mesh.  When I merged it into the Road scene, it was all brought in and scaled.

I’m curious where you got that model from.  The one dummy object said something about FBX.  Was this from Maya?

3DS Max Design 2011 64-bit - Advantage Pack
Dell Precision T5500, Dual Six Core Xeon X5650 @ 2.67GHz, nVidia Quadro 5000, 24 GB RAM, Win 7 Enterprise 64-bit
Minneapolis, MN, USA

Its a dosch design’s model. Dunno which software they use to make the model. It worked with the attach and delete way :).

3ds Max 2009 64-bit
Core2 Quad @ 2.4GHz, GeForce 9500GT, 4 GB RAM, Win XP 64-bit
Kathmandu, Nepal

You don’t scale at object level don’t you??

just kidding. :P.

But don’t. Really.

Mental Ray - 3ds Max 2010.
Nothing more, nothing less.