Blender units?

I’m having difficulties with the concept of a “Blender Unit”. It seems to be a bit fuzzy. Any time I create a mesh, the shape appears to extend from the origin in each direction by one grid unit. In the case of a circle (and derivatives, sphere, cylinder etc.), it is drawn as though a compass had been placed at the origin and with its drawing edge touching the nearest grid corners (ie (1, 1), (1, -1) etc), rather than touching the grid lines. I found this a little surprising. It means that the radius of a circle is not equivalent to 1 grid unit, but root2. Is there any good reason for this?
Secondly, I am frustrated by the way an object has its location, rotation and scaling attributes reset to 1 after each transformation. So if I scale a newly created object to a particular size, lets say 5, then later decide I want it back to the the former size, I hit Skey and see that its dimensions are all now described as 1, rather than 5 as I left it. So to return to the original size involves scaling it to 0.2 of its current size. Is there an option to show absolute values of location, rotation and scaling, in preference over relative values? I think this would be very valuable.

Select an object and hit “n”.


I have a followup question to those that know more about blender than I.

What are the hotkey’s to make the current obj’s attributes the default for that object? IE keep it the same size but reset its “size” attribute to 1?

Also, what is the hokey to recalculate the object center, without having to move all the verticies around? I thought that there was an option to calculate the center of the total verticies of an object, and then change the objects center to that spot, but without the side effect of having the verticese move…

that’s bit confusing… like if you have an object precisly placed, but the objects center is 20 units off to the left. Normally you would have to go into edit mode, select the verticies, move them like 20 units to the left to “center” the object, and then go out of edit mode and move them back.

Is there a command that just moves the center without moving the verticies?

To Hamlet:
The first question is a good one, but can not answer that!?

The second one it’s easy:
If you scale in editmode, the object gets the new size as 1. If you scale in object mode, the object gets what you want (test the scale modes with “N”, where you see Sizex, ect…). If latter you whant to reset to size 1, or rotation 1, or position 1, press ALT+S, ALT+R or ALT+G, respectively. If you want to apply the new properties, press CTRL+A to chose Apply Size/Rot.

To MacGyver:
Half question is already answered.

There’s no hotkeys, afaik, to reposition the object center, but you have in EditWindow 3 buttons: Center, Center New and Center Cursor. Just keep the mouse above each one and read the tip.

in the object buttons, there is a button labeled “Center Cursor” which puts the center where the cursor is. Also, “Center New” places the center at the middle of the object. (Note: you have to be in object mode for this.)

I don’t know the hot key (or whether there is one) but I have found a button which does what you want. In the Editing button panel (F9), it is there under the ‘Mesh’ tab. There are 3 buttons, Centre, Centre New, and Centre Cursor. Just placing your mouse cursor over the buttons will bring up a description of what it does. I think the middle one does the job you are looking for: Centre New - shifts object origin to centre of object data.
Hitting “N” does give me precise numerical control of how I transform my object in Size, Location or Rotation, but each time I do it the X,Y and Z values are each set at 1. I would like to know if it is possible to make them display the value which I confirmed at the end of the previous transformation. An example: I create a circle in top view, hit Skey then Nkey to change X value only from 1 to 2. Everything else is left alone. I confirm with LMB or Enter, and an elipse shape results. Then I hit Skey followed by Nkey again and values X,Y and Z are all 1 again. So if I want to change my elipse back into a circle, I have to remember that I had changed X from 1 to 2; and since X is now set to 1 again, I have to change it to 0.5 to acheive the original shape again. To me, it would make a lot more sense if when I hit the Skey for the second time, the X, Y and Z values were 2,1,1 as I they were when I confirmed the last transformation. Surely Blender offers this as an option, no?
I hope that is clearer.

Lines crossed there.
MadCello, thanks but it’s still not working for me. The CTRL+A command is useful, I didn’t know about that. If i use it, then it seems to create a ‘bookmark’ for current attributes, which can be reverted to with the ALT+S/G/R commands. However, whether in Edit or Object mode, I still find that 1 is the starting value for transformations of size or location ('scuse me, it is of course zero for rotation). No matter what I do. Bizarre.
So my first Question remains a riddle for now…

lol don’t hit “s”.

Follow my original post and just select the mesh and hit “n”

A dialog box will come up providing all the info you want and have been asking for.

Don’t be in Grab, Size, or rotation mode.

Just hit “n” and a dialog box comes up listing LocRotSize values, that are precise and don’t reset.

When you finally get a location/rotation/size that you like, hit ctrl-a to reset the object’s values, so you can backtrack later on by clearing those values.

Finally, any resizing, moving or rotation you do while that “n” window, also known as “transformation properties” is closed, will still be reflected by the window.

So if you have an object that starts at size 1, and hit “s” to resize to like 5.4, when you open up the window with “n”, it will say 5.4. And if you scale that model with “s” 1/2 down, then the transform window will say “2.7” because that is .5 of 5.4.

So, in short, hitting N with the object selected will show you the absolute values, just like you’ve been wanting to the whole time.

Well, if you want to adjust your scale ‘absolutely’, why not just hit ‘n’ and scale it directly in that panel?

I think what you’re asking is if it is possible to have those absolute values which normally appear in the numeric panel [n] appear in the 3DWindow header, which I don’t believe you can.

Thanks! I was stuck in a groove, couldn’t stop hitting S! The menu brought up by N is everything I was looking for, can’t believe I was so dense to miss it. Everything makes sense now.

Oh yeah, except for my original question!

Oh yeah, except for my original question!

To clarify: the position/scale/etc. are still resetting to 1 every time you transform your object?

Are you sure that you are performing your tranformations in object mode, not in edit mode?

That still sounds like the root of your problem…
Either that, or there is a bug in the version you are running - mine doesn’t do what you are describing… :-?

Have learn’d another!!!

Didn’t know that the Transform Properties window (N) also updates in “runtime”.

Blender is every days amazing!!! :smiley: :smiley: :smiley:


He means that each time you hit “s” or “g” or “r” it starts at 1 or 0. The reason is that normally when changing an object, you want to make it bigger or smaller than what it is RIGHT NOW, and now what it started at.

But his first question was actually why are circles given a default radius of sqrt(2).

That’s a good question and one only the original author of blender could probably answer.

Perhaps it is just so that you can inscribe the circle with a square…

Just a thought, but if you want, you could scale a circle down so it is perfecty down to radius 1, both a circle and both spheres, throw them on layer 2 perhaps, and hit “ctrl-u”. That command saves the current blend file as the default, so then everytime you start up blender you will have circles and sphere’s with radius 1 staring back at you.

Really though, I always end up scaling all my objects anyway… does it matter what it starts out at?

Sorry to resurrect an old thread, but if there’s no fix, this issue is going to prevent me from using Blender at all when Blender looks ideal in every other way. I’m new to Blender, so I may be misunderstanding, but the problem isn’t where the measurement starts or ends, it’s the difficulty in knowing what size an object is.

Even after I use N to set the precise dimensions of an object, none of it makes sense to me. A sphere with SizeX, SizeY and SizeZ all set to 1.000 actually has a radius of 1.414. Therefore none of SizeX, SizeY or SizeZ is the radius – which is pretty much the only size characteristic a sphere has, although I’d settle for specifying the diameter :-).

The size of a NURBS sphere is the radius, but a NURBS cylinder’s height, the SizeZ component, is scaled by a factor of 2. That is, if the SizeZ of a NURBS cylinder is 1, the actual height of the cylinder is 2 units.

If I were to design in Blender, I’d have to constantly be multiplying and dividing by root(2) and 1 / root(2). Is there no way to configure Blender to display the units differently? In “mathematical” style, for lack of a better word? Is there a plugin that will convert these figures? Is some kind of fix in the works with the devs?

Blender isn’t really a precise drafting/CAD tool, and it seems like you are looking for something like that. However, if you really want your circles to have radius 1, and your NURBS stuff to have the right measurements, (and I never use NURBS anyways, prefer subbed meshes :P) go into editmode, size the object to what you want it to be. this won’t change the dimensions of the object. Alternatively, scale circles to 1/sqrt(2) and hit alt-a to change its dimensions to 1 again. In most cases, I find that just lining things up manually, sometimes with the help of gridsnapping, scaling along an axis or a couple levels of zoom, provides enough accuracy to suit me.

Newly added planes, circles, spheres and grids have a vert at (1,1,0). Newly added cubes, cylinders and tubes have a vert at (1,1,1). It’s just the way it is.

If you want, just after adding the circle/sphere you can press S . 7 0 7 ENTER and it will have a radius of 1. Then next time you scale it the relative size is back to one again, so you don’t have to worry about the root-2 anymore (see? it is useful :stuck_out_tongue:)

True, I must have some degree of precision. If I use 1 unit == 1 meter, then I have 1 mm precision in the N box, and 0.1 mm precision in the S command. That’s plenty for what I need.

I’ve been reading and, and I think some frustration may come from the fact that if Blender is this close to being a reasonably powerful CAD program. If Blender added and slightly modified a very few features, it would have a lot of CAD already, and the ability to expand those CAD features easily. People who don’t use the CAD-ish things wouldn’t even know those features were there.

Thorwil on the boards said, “In my experience some people fear that CAD means ugly, complicated software for engineers (not suited for designers or artists). Even if that would be the case for all available software, it still could be changed.” I think this is exactly right, the CAD elements could be added with minimal changes, and no changes to Blender’s look and feel.

Also, there are few GPLed CAD tools for Linux, and so far I haven’t found one I like. Blender is GPLed, works on Linux, and has the complexity and power of emacs, so I’m already a little bit attached to it. :slight_smile:

I don’t know enough yet to prefer NURBS or subbed meshes. It seems like NURBS is more of a special feature and and subbed is the regular way to do things, so I’ve been avoiding NURBS while I’m still learning.

This is what I’ve ended up using, but it seems to be the ctrl-a key now, “apply size and rotation”. Once I set the measurements of cylinder, sphere, et cetera, to the “normal” – AKA “what I’m used to… me, me me!!!” system :slight_smile: – then I use ctrl-a and the mesh sizes like I’m used to. My only concern is accidentally pressing ctrl-a again in the future!

That’s cool, too. I like that the scaling adds a digit of precision. I just want to be able to set the absolute size.

Thank you both for posting, this will get me going in Blender. I’m willing to bet that the more CAD-dy stuff will be added over time anyway, given the overall quality I’ve seen in Blender so far.