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My question is: why do Object mode scaling and Edit mode scaling seem to be incompatible? I'm quite new to blender, so I may not know sth important about these modes. The actual case is: I create a cube, which is 2×2×2 metres in metric units by default (it's also shown under 'dimensions')

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Then, with the cube selected, I switch to Edit mode, and enable 'Edge info: Length' under 'Mesh display'

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And it shows the cube's measurements, which are 2m on each edge. Now I use the scale tool in Edit mode, making the edges 2.244m

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That's good so far. Changing back to Object mode, the changes can be seen under 'dimension'

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However, when I use the scale tool in Object mode, the scale and dimensions also change, but changing back to Edit mode, the measurements shown remain the same

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So the question is, why does the scale tool work differently and have different effects in Ojbect mode and Edit mode? Also, how can I enter the desired size of my cube manually to get an accurate result, without using the scale tool in Edit mode, and without changing the scale ratio in object mode?

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    $\begingroup$ scaling in object mode you are scaling the local space of the object ( also stretching the object to keep the verts in their local pos ), you are making 2 m in local space equal 3m in world space (but it still 2m ) , apply scale should help $\endgroup$ – Chebhou Apr 16 '15 at 13:10
  • $\begingroup$ Related: blender.stackexchange.com/q/12288/599 $\endgroup$ – gandalf3 Apr 16 '15 at 19:32
  • $\begingroup$ This is how you set dimensions in edit mode manually: blender.stackexchange.com/a/68678/28015 $\endgroup$ – JakeD Apr 27 '18 at 0:27
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The object-mode scale is a property of the object; it doesn't actually do anything to the mesh, but rather affects how the mesh is going to fit in the scene.

Scaling in edit mode actually moves the mesh around; it's equivalent to selecting and carefully moving vertices around to make the mesh bigger or smaller.

There are many situation where you don't want to touch the object scale (e.g. physics simulations tend to get mucked up).

If you have changed the object scale, but really meant to scale the mesh, you can "apply the scale" (i.e. apply the object's scale to the mesh, and set the object scale to 1) by ctrla and select "scale" in the popup menu.

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  • $\begingroup$ thank you, and how can I enter accurate measurements manually? $\endgroup$ – Tom Apr 16 '15 at 17:24
  • $\begingroup$ Blender probably isn't the best tool for that sort of modelling (although there may be plugins out there to help with it). To try it though, you might find it useful to hold the shift key while doing the transformations - this is used for more precise tweaks. $\endgroup$ – ajwood Apr 16 '15 at 17:30
  • $\begingroup$ there is a picture of a magnet in the 3d view header if you enable that button you can choose snap to settings to the immediate right. I find snap to increment,edge, or face all very useful $\endgroup$ – Mr. Manager Sep 29 '15 at 11:52
  • $\begingroup$ @Tom Like this: blender.stackexchange.com/a/68678/28015 $\endgroup$ – JakeD Apr 27 '18 at 0:28
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I am not sure if it was explained well yet. Each object has a bunch of properties including properties to delineate it's dimensions, location, rotation, vertices positions, etc.

Changing any location, rotation, scaling and dimension property in object view only changes the property of the object that effects it's relation in the scene compared with other objects.

Changing any location, rotation, scaling and dimension property in edit view only changes the property in reference to the objects origin/pivot point which directly affects it's relative scene data.

So for example:

Scaling an object in object mode by increasing it's size 10x (hotkey s10) will make it look 10x the size in the scene and if you look at it's objects edit mode length's they remain the same

Whereas:

Scaling an object in edit mode and selecting the whole object (hotkey a) and scaling it's size 10x (hotkey s10) will effect the dimensions you see in edit mode as well as the dimensions in object mode since the actual object is 10x larger and should be reflected so in the scene.

This brings about a reason why people reset the object scale to 1x at various points in there project with Ctrl-a applying scale and rotation. Knowing that resetting the global scale (scene scale) to 1 in the X, Y & Z planes will make an object understandable from a users perspective.

Example 1) I model a 3d car and look at it in the scene. Normally you would want it's scale set to 1x so you have a simple relationship to other cars in a scene.

Example 2) It can make calculations easier. Imagine animating an FFT for spectrum analysis of audio waves. You can have an X base of 1.35 units, Y base of 35.56 units and Z base of 3535.5 units on an object you plan to animate and you want to move X in relation to Y in a 2 to 1 ratio. Debugging oddities is simpler at the lower branched levels of mathematics.

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