Understanding this scale malarkey!

I’ll start by saying I’ve read a few posts on size and scale and I’m more confused than when things just didn’t fit. Now things don’t fit and by head feels like it’s on backwards!

I know what a meter is, I know what a millimetre is, I also kind of understand what an inch is. I get the idea that Blender doesn’t really have a unit of measure, it makes me feel a little squeezy, but I get it.

What I don’t get, is how to resize objects in a scene and change their bloomin size, or to be more precise, which viewport mode does what.

I have a model here at the moment which I’ve designed, I stated with a 20mm cube. I know it was 20mm using the ‘lines’ check box in properties toolbox. Somehow, during the modelling process I’ve managed to increase the size dramatically, now I don’t doubt I’ve done this, but I don’t remember being responsible!

What really boils my head is resizing an object doesn’t change it’s size. I had one design yesterday, that on screen, measured 100x25x10mm. When I transferred it to my printer software, it had to be magnified 1,000 times to be 10mm in length. So I’m obviously not getting this size/scale business, and I haven’t had it explained in a way my head can grasp.

Rescaling/sizing/bending the laws of physics in design mode isn’t always that simple when you have a complex object fade of different parts that all rely on each other, so I have to get my brain box around this.

Is there anyone else out there who struggled with this and found a page or article that explained it well to a person with a half decent understanding how physics works and the Fact that making something smaller makes it bloomin smaller!!!

Thank you. :wink:

Blender does have unit measurement in Scene Tab. If you want to see measurement on edge of objects. There’s an add-on. Just search for it on google and learn how to install add-on into blender.

Short answer: Press “ALT-S” in object mode with the offending object selected and all your problems will go away.

Long answer: Blender tracks mesh data separately from object data. For example, take a look at these two perfect default cubes.

All the edges are 2 units long, so they are all the same length. The objects also share mesh data, so they are exactly the same size. What’s that you say? They don’t LOOK the same? You’re right! That’s because, while the MESH is the same, the OBJECTS that are using that mesh are different. Specifically, one is scaled:

and the other isn’t:

This scale on the objects can be really confusing, especially when you’re taking measurements in edit mode off of the MESH, but then exporting geometry, which includes the OBJECT scale.

To fix this, you can do either of the following:

  • Apply the scale (CTRL-A, 3) which will keep the OBJECT size and update the MESH to match.
  • Clear the scale (ALT-S) which will keep the MESH size, and update the OBJECT to match.

Either of these will make your export size match the length numbers you see in edit mode… unless you have objects parented to bones with scaling applied, or parented to other scaled objects and then you clear the scale on the parent, or, you know what, nested transforms are complicated okay!

As I used and mentioned in my post.

Oh man, I feel like my head has been blended! Ok. I think I kind of get what you’re saying. I’ll do more testing tomorrow after I’ve read your thread a couple more times. That’s clearer than I’ve read elsewhere so far. Many thanks.