metric precision

Despite the fact that Blender is not intended to be an CAD(Computer Aided Design) tool it can deal with numbers very well and can be used as a very precision tool for modeling in interior or architectural design.

Before starting any modeling you have to set up your unit of measurement. I will go for metric [later on i will describe a imperial unit setting] and i choose 1BU (Blender Unit) = 1M (Meter) [this gives a good raport between real word scale projects and Blender internal settings ]. So your reference scale will be the default blender plan which will appear as 2x2M.

With a new file in blender press NumPad7 to be in top view, press XKey>Ok to delete the cube from default scene and add a plane with Add>Mesh>Plane.

You have a plane in edit mode with all four vertices selected. In Edit button panel select Edge Length and you have the length for selected edge.

Moving around .

You can chose to move only on the grid by setting this in User Preference window. Note that if you zoom in the grid is subdivided, so the snap will move on subdivided grid too. My preference is to leave Snap to grid alone and when I need snap I press CtrlKey.

As a practical exercise I want to change the proportions of my 2x2M square to an 1x1.62M golder ratio rectangle. First press BKey to select the top two vertexes and press GKey, CtrlKey to move them 1M down and press LMB [left mouse button].Note that RMB will cancel the action. The header of the 3d window is transformed into a data display and you should read only dy=-1 . Zoom in till the grid is subdivided and select only the right two vertexes. Now press Gkey, Ctrl+ShiftKey to move them to the left till you got 1.620 on top and bottom edges of rectangle. If you zoom in to subdivide again the grid or use Ctrl+ShiftKey combination you can increase the precision to 1.618 a better approximation of golden ratio.

Here is another way to achieve the same result. Use Ctrl+ZKey to undo all the operations. With all vertexes of the plan selected press SKey and CtrlKey to scale them 0.5. Select the right two vertexes press GKey, Xkey to constrain the movement on X direction and enter 0.618 on Numpad Key. You got the same result

Another very helpful tool is to use Shift+SKey, Snap menu. Let's say that you cut a plane [KKey>Knife(Exact)]and you want the new vertexes to be on grid too.

Simple select them and Shift+SKey>Selection Grid to move them on the grid. Using Cursor>Selection option to move the cursor to a vertex location you can change the center of the object to that vertex location. Press TabKey to be in object mode and in Edit button panel Mesh tab press Center Cursor button . In this way you have the center of the object to a precise location too.

Now with the mouse in 3d window press NKey and you have Transform Properties windows. Pressing NKey again you hide the window. Play around with the object by moving rotating or scaling and with the vertexes in edit mode to see how the values are changes. If you want to translate an object on X just type in the value. You also can lock an object value by pressing the lock icon.

Cube on the floor

Let's do a very practical exercise and go File>New>OK. You have default scene with the cube [or add a cube]. Move the cube's origin to the bottom by pressing TabKey [to be in edit mode] select the bottom four vertexes and Shift+SKey>Cursor>Selection. Press TabKey again to exit edit mode and press Center Cursor button in Edit button panel Mesh tab.

Now the origin of the cube is in the middle of the bottom face. Press NumPad1 and NKey to see the Transform Properties window. LocZ number button is -1.000. Click in the middle of this button and type 0. Now the origin of the cube is on xy plane.Press NumPad7 to be in top view [your 3d window should say Top in the upper left corner] and press Shift+CKey and again CKey. The 3d cursor is in the center of the xy plane and in the center of the 3d window.

Add a plane with TabKey>Add>Mesh>Plane, scale it with SKey and drag the mouse. Press TabKey to get out of edit mod and NumPad0 to be in front view. If you consider the plane as a floor you see that the cube is on the plane . This is a good way to set the objects on the floor considering the floor on xy plan and a ease way to manipulate the objects.

The 3d cursor can be set to a exact location in View Properties window. The 3d cursor is a place where a new object is created. Go View [in 3d window head menu]>View Properties...or click LMB in top and front view and Shift+SKey>Cursor Grid to set the cursor to a grid location

Imperial Units

You can't set imperial units in Blender but is a very easy way to go around.

In View Properties window set Spacing to 0.1 and Divisions to 12

Now the grid is set to 12 divisions and the reference default plane is 2 in square. So 1BU is 10 in [10"] and if you want to move an object 1 foot [1'] you have to type 1.2 on keyboard.

And again 1BU=10" is a good raport between real word scale projects scales and Blender internal settings. A issue may arise when you work on a project in metric and want to append an object from another file who was done in imperial, but this have a ease fix too.

When you work in metric and append an object from a file with imperial settings to get the actual metric dimension scale the object 0.25 times and Ctrl+Akey to applay scale.

When you work in imperial and append an object from a file with metric settings to get the actual imperial dimension scale the object 4 times and Ctrl+Akey to applay scale.

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