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Genecks
05-Apr-07, 22:07
I know this has been discussed; a thread about this is on the same board-page of this thread. However, I have wondered about the unit scale for Blender. I've been viewing people argue about this thing for over 8 months or so. I've decided to get back into blender from a year ago, since I want to be able to create some 3D visuals of things.

Now, I'm not an engineer (I have science and math background), but other than that, I keep seeing discussion about "blender units."

Now, since the days of Greece and Rome, people have socially constructed various units of measurement. People have used the hand as measurement and more. However, I'm thinking Blender is a little more "constant."

The concept here is a thing called a constant. Are blender units constant? IF a blender unit was equivalent to one foot, then (blender unit)(blender unit) = 144ft^2

The problem with ancient measurements is that not every man's hand is of the same dimension. Are blender units constant? At any time during user usage do they change? If not, then I assume a blender unit could be assumed to be virtually any unit. Well, maybe not amperes or voltage, but you get the idea.

I guess if they can be assumed to be any unit, then the next problem would be zooming and scaling. I'm pretty sure 100 picometers would be quite the annoying thing to zoom out of. heh.

Is it possible to control the units when creating new objects? I assume that's the most important thing. In other words, if I wanted a 4x4x4 blender-units cube (not cubed, but the cube is 64 blenderunits^3), could I obtain that? How do I manipulate the unit variables of objects, such as cubes, circles, and cylinders?

Vertex Pusher
05-Apr-07, 23:22
Yes I agree with you that some people make a rather odd deal out of the fact that Blender does not have units conversions . But the fact is a Blender unit is half the standard cube or plane when first created (or quarter if you are talking about area) . And that's it . No matter how "zoomed in" you are the method of creation of the geometric primitives available in Blender is based on Blender units (and generally it's 2x - but I haven't tried all primitives not to mention Suzanne :)) . So if you decide that a Blender unit is = to an inch that is what a unit of measure is for that file ... now people get over it ... it's not that abstract .

Genecks
05-Apr-07, 23:33
Hmm. I'll work out the x-y variables and algebra when I have a bit more energy. The only things that seemed abstract to me were the constants and proportions. More people talked with words than numbers whenever I viewed information about units in Blender.

Mike_S
05-Apr-07, 23:37
Actually for whatever bizzare reason, one B.U. is dependant on the View Properties / Grid Spacing. Bring up that dialog, and change that setting while creating a couple of cubes, then press N to display the properties for each cube, they will both say 1.0 / 1.0 /1.0 even they are not the same size ;)

Units / CAD . precision etc has been discussed here many times, there a couple of huge threads on it. I've never read the details on what was (if anything) resolved on how to work with precise units, as the stuff I do, I just size "by eye".

Mike

Vertex Pusher
05-Apr-07, 23:42
EDIT : OK so I think I answered the last part of your question ... no, you can't create a 4X4X4 cube when you first create a cube in Blender . It will always be 2X2X2 ... but you can always scale it up or down to the size you need ... You have to give up something to be flexible relative to the UI ... because it is smarter in a lot of situations to have no units assigned to methods of object creation relative to the UI because you never know when some boob decides he wants a .00004X.00004X.00004 cube in a viewport that is set up for viewing whole numbers ... The point is that you determine what a unit of measure is after the fact, because scale is, and to quote an old Renaissance saying "Man is the measure of all things", relative . And now that in 2.43 you can set the grid divisions to English measures and such people should just get over this "fault" in Blender .

Genecks
06-Apr-07, 00:07
And now that in 2.43 you can set the grid divisions to English measures and such people should just get over this "fault" in Blender .Could you point me to a link that discusses this attribute?

Anything below this is assumption. Don't take anything as absolute truth or fact. I'm philosophizing Blender

Let me see if I'm understanding you correctly:

I can create an environment for set variables and constants. From there, I can't change those set variables without screwing EVERYTHING up. If I want some other standard for measurements of higher or lower scaled proportions, then I need to create another document?

For example, I can have units that I can treat as if they were atomic measurements, but I can't really start manipulating those units to act as miles. I can have units within a seperate environment that I can treat as if they were yards, but I can't treat them as if they were centimeters. If I tried doing that, the proportions and scaling according to the plane and grid would not be correct, because the grid planes are at a set, virtual unit of measurement.

In other words, an environment with a 2x4 piece of wood created by 1 Blender-unit squares (which in this environment are acting as feet) isn't going to be able to create a molecule of deoxyribose nucleic acid because the environment is not going to take that 1 blender-unit square and bring it down to a fraction of its current dimensions (virtually, idealistically turning the BUs--which are conceptually and currently standardized at 1 ft--into 1 Angstrom unit).

So, in an environment, I have a choice of what ideal units I'm going to use. I can't have meters and miles if I want feet. I can only have feet. I can't have inches, because I'm only allowed one type of unit. I'm not allowed to have two conceptual types of units within a document. If I want to conceptualize and draw with a different unit of measurement, then I need another document.

In conclusion, one ideal unit of measurement per document. Right?

If (document),
then Blender unit = desired unit.
However, only one desired unit is allowed per document, because the blender unit must stay constant.

If blender unit = feet
and blender unit can only equal one measurement
then trying to use inches would make all foot long objects divided by 12.
Proportions would be incorrect.

foot = BU = 1:1 ratio
if BU converted to inches
1 inch : 1 inch ratio becomes 1 inch : 12 inch ratio (a foot long object becomes one 12th of its size)

an new item that was 3 inches (3 inches : 12 inches) becomes looks as though it is three feet ( 36 inchs : 12 inches) because of the new unit adjustment

Proportions are false. (and they wouldn't look right)



Hmm. Well, if this is true, then I assume the millimeter would be the best bet for most household things. One must predict and account for his or her ideal, desired unit based on the current proportions he or she is working with.

Maybe if there were a way to mix formatting settings of blender documents and customized setting without and overlapping and constant and proportions, then a person could set these things to work just right.

Possibly another problem is that a person has to round to the nearest whole number. Is that correct? It's impossible to get .75 of a blender unit. Therefore, a person has to 1 blender unit. Instead of 2.78943, a person must use 3 blender units.

Interesting. Therefore, depending on the size of objects being done, the unit of measurement would be taken into great consideration. The smaller the measurement, the better--but probably more time consuming.

The fact that a unit must stay constant creates a constraint when creating detailed models of things. I suppose for Blender, using units as decently small units based on one's environment of design would allow for the decent creation of something. However, the constraints limit the effectiveness of this program to be used for CAD.

If I'm seeing all of this correctly, I figure Blender will work for architecture and CAD if a person is using very small measurements and predicts the best measurement unit for the design. Because of the constraints, getting exact measurements is impossible. A person would have to round the numbers to whole number integers. For engineering and other complex designs, I wouldn't think Blender to be a wise idea. However, if I'm correct, it would not a bad one for making a virtual design. Yet if it isn't going to be exact in the end, I figure it's better to put it on paper.

I guess if I'm not going to design things for research and development, then building detailed things isn't much of a worry in Blender.

It would be pretty difficult to take an original design and convert it into Blender, because a person can use only one virtual type of unit at a time. And to use units, such as angstroms, to create an object--such as a delorean--would take LOTS and LOTS of time or work. Maybe the computer couldn't handle it. Because of the time vs. work thing, it'd be quicker to do stuff in an engineering program.

RJ2005
06-Apr-07, 08:49
Suggestion

YOU CAN MAKE A 4 X 4 X4 X CUBE IF YOU USE A SCRIPT LIKE
BMAE & Caliper for arrows & dimensions


BMEA
http://www.blendernation.com/2006/07/06/metricstandard-unit-mesh-creator-script/
http://www.geneome.net/blender/hostedfiles/BMAE%20v1.zip
Caliper
http://www.blendernation.com/2006/05/06/cad-tool-caliper-script/
Salutations

Vertex Pusher
06-Apr-07, 21:09
First of all you can change the grid spacing by going to the 3D window header -> View -> View Properties which will open the View Properties window and in the first combo field the last one, "Divisions", can now be changed to any number you want . So if you decide a BU = foot you can subdivide the grid to 12 so each subdivision in that set up is equal to an inch .

And also like Mike_S said you can adjust the BU in a file itself by adjusting the Spacing value . So I guess if you wanted to double that to 2.0 and created a cube you would have a 4x4x4 BU cube ... So I discover myself to be wrong about that one . But it is still a 4x4x4 BU cube so the BU as constant still holds true . The 1.0 / 1.0 /1.0 scale only holds in Object Mode, if you tab into Edit Mode and turn on Edge Length from the Mesh Tools 1 panel you will see that it is 4.0/4.0/4.0 BU long .

And your "philosophizing Blender" does not make any sense to me ... If you have a set up, and lets just make it easy the standard unit setup in Blender (which I always assumed to be metric) and decided that the BU = meter and added a cube you would wind up with a 2x2x2 meter cube by default . But you want a 1x1x1 meter cube in the scene so you scale it by 0.5 to get your cube . Now you want a cylinder that is 3.0 decimeters in diameter and 2.5 centimeters thick . So you create a cylinder and the default is 2 BU (meters) in diameter and 2 BU in thickness . So you scale along the diameter by 0.3 and scale by .025 in thickness ...

So where's the incompatibility in that ? I don't understand your assertion that "Proportions are false. (and they wouldn't look right)" ... Somehow it seems to me that you have misunderstood the entire idea of scale and measure ... the BU is a measure but just not tied to a specific system of measurement . And scaling relative to that unit gets you proportions which makes design possible ... I mean Blender is a 3D development environment ... how could you produce anything with out a unit measure even if not explicitly named ?


Possibly another problem is that a person has to round to the nearest whole number. Is that correct? It's impossible to get .75 of a blender unit. Therefore, a person has to 1 blender unit. Instead of 2.78943, a person must use 3 blender unitsAnd that's just wrong as I showed above ... a BU is capable of fractions to three decimal places .


The fact that a unit must stay constant creates a constraint when creating detailed models of things. I suppose for Blender, using units as decently small units based on one's environment of design would allow for the decent creation of something. However, the constraints limit the effectiveness of this program to be used for CAD.Also false . A BU is a number (the number 1.000 in fact) not a constant unit . It is up to the user to decide what the numbers stand for as a unit of measure . I think this is where you are getting confused ... A BU is a constant as a unit of measure not a physical or mathematical constant . It just does not have a set convention of measure it explicit calls on (such as a foot, meter etc.) . Or to state it another way a Blender Unit is the measuring convention in Blender .

You can do precise work with Blender if you determine what a BU stands for relative to other measuring conventions . If I decide that a BU = decimeter then I can design things with that in mind . The BU does not prevent me from determining the relative scale of objects and surfaces .


It would be pretty difficult to take an original design and convert it into Blender, because a person can use only one virtual type of unit at a time. And to use units, such as angstroms, to create an object--such as a delorean--would take LOTS and LOTS of time or work. Maybe the computer couldn't handle it. Because of the time vs. work thing, it'd be quicker to do stuff in an engineering program.Ok this last one is just silly ... who or what crazy institution would want to model a delorean in angstroms ? I mean just think of the computing power required to do that ...

CD38
07-Apr-07, 11:00
And to use units, such as angstroms, to create an object--such as a delorean--would take LOTS and LOTS of time or work. Maybe the computer couldn't handle it. Because of the time vs. work thing, it'd be quicker to do stuff in an engineering program.

Ok this last one is just silly ... who or what crazy institution would want to model a delorean in angstroms ? I mean just think of the computing power required to do that ...


That's the beauty of Blender's dimensionless world. If you want to, you can render a Delorean inside an atomic nucleus, or the size of the Titanic, no problem. I don't understand why people think Blender needs to be a physically accurate simulator, whether in dimensions or fliud sims or rigid bodies. We're not going to model the entire Earth on our Mac Minis.

Visnik
10-Nov-09, 12:37
here is why, Group efforts, If Johny for example decides he is going to model in feet, bob decides, cm and Jeff just doesn't care, when all models are brought together the passenger of the delorean my be 50 times bigger or smaller than he should be. This is from my experience with other applications such as 3DS Max. Now, as long as the unit is agreed upon from the beginning you can achieve that result.

almir
10-Nov-09, 15:12
I need help..
Why edge length vertical and horizontal is not same size..
I'm stuck in the middle of modeling because of this..

========================================
XP SP3, old sempron 2800+ OC 1,6 to 2,2GHz, 768MB, nvidia 256MB
Blender 2.49b
http://fbp0aa.bay.livefilestore.com/y1pXamlXoKsEH_3A4UqYYGRGZ5s5NM5JsCMDS7kn787QLK7dUl Y15ilNWJQyGxbZpWIvUEKwQzmIrpFimg-XL4-qiSl5fKsmvGn/image.jpg

Spectre-7
10-Nov-09, 16:36
If you scaled it in Object Mode, those changes won't be reflected in Edit Mode. To fix this, go back into Object Mode (Tab) and Ctrl-A to apply the scale. When you go back into Edit Mode, the edge lengths should be correct.

almir
10-Nov-09, 16:51
thanks.. it works

beeman
10-Nov-09, 20:59
I'm very new to Blender - but since I saw this thread...I'll ask the simple question:

I was wondering if blender can be used in a CAD-type capacity to design to precise units. From the previous discussion, it almost sounded like one cannot model objects in fractions of a Blender Unit?

Don't get me wrong...I understand Blender is not a CAD tool...and I'm not suggesting it should or could be...I am just wondering if it could be applied to model an object which has known dimensions that may be non-whole number of the given units.

beeman
10-Nov-09, 21:01
oops..the thread above stated the BU can be up to 3 decimal places...sorry for the double post