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Getting Started




3D Coordinates Blender Units Video Tutorials




There is a wealth of information available on the Internet in the form of manuals, guides and tutorials, that cover the full potential of this program. This is intended as a starter for people interested in the creation of  dimensionally accurate models. A list of useful places to find information is detailed on the links page.

Getting and loading Blender


On the Links page follow the link to www.blender.org. Once on the site, click the download link to open the download page. Choose the file to suit your operating system and follow the simple installation instructions at the bottom of the download page to install the program.

What you see when the program starts


When you run blender for the first time you are presented with the default screen. It contains the user preferences window at the top of the screen. The main 3D work area in the centre of the screen and the buttons window at the bottom of the screen.

Relevant sections of the program

When you first start modeling the main two screens are already open. The 3D workspace and the Buttons window.
A cube object (1) is In the centre of the 3D view  and the window is orientated so you are looking down onto the top of the cube. their is also a Lamp (2) to illuminate the cube and a Camera (3) to output a 2D bitmap of the cube.
Blender Start Screen


3D View: Header Bar

Header





1) Window Type
Click on the window type button a a menu will appear showing all the different window types. Each window has a function within the creation of animations. However our initial interest is with the following windows:

3D View
Buttons Window
Outliner (when we build assemblies of components)
Script Window (to run useful scripts)

2) Pull up menu
A context sensitive menu showing the operations that can be carried out and the keyboard shortcut for that operation.
Windo Types
3) Mode
The operating mode for the window. Initially we will only be using Object mode and Edit mode.
Object mode is where assemblies of components are constructed.
Edit mode is where the individual  components are modeled.




4) Draw type
This is the way the model is displayed on screen. The two useful types we are interested in for modeling are Wireframe and Solid.
View Type & Draw type

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5) Pivot Point
This gives a choice of centre points for rotating and scaling the 3D models.
Pivote Points
6) Widget control
Click the hand icon to de-select this. It should show a light gray background

7) Layers
These allow you to organize components in big assemblies, only showing those that are needed.
Widget & Layers





Context Buttons
These change the control button options in context with the operation you are performing.
Context Buttons





8) Material Context Button
Brings up a choice of material texturing and lighting options
9) Editing Button
Brings up the modeling tools
10) Render Button
Controls the output to a 2D bitmap image
10) Material Sub-context
Each context button has sub context options.





Understanding 3D coordinates and Blenders 3D views




Blender Coordinates When you first run blender you are presented with a view of the workspace looking directly down from above. The screen in this position represents the X and Y axis. The Z axis is coming away from the screen directly towards you.

You can change the view direction by either clicking and holding the middle mouse button whilst dragging the mouse to rotate the view, or using one of the preset views accessed via the number buttons on the right of the keyboard.

Num Pad Buttons

When modeling in blender you draw parallel to the surface of the view at the depth of the selected object/vertex, so the view rotation is important to the desired outcome.  





Blender uses the right hand coordinate system with the Z axis pointing upwards. This is in common with the coordinate systems used by most common 3D CAD packages. Its worth noting though, that some programs use a coordinate system where the Y axis points up and it may be necessary to rotate the model if exporting your model into a program with this configuration.

Blender displays the coordinate as:
DX 0.0000 DY 0.0000 DZ 0.0000 (0.0000)
When moving or extruding a vertex the bracketed figure denotes the distance from the start point and DX,DY,DZ will change relative to the distance along the axis relative to the start point.


In object mode The Transform Properties panel displays the objects  position relative to the global coordinates it also gives details of its rotation, scale and bounding box size.


Transform Properties  The object centre coordinates of the blue cube in the Cartesian coordinates diagram are displayed in the Transform Properties window.
Cartesian Coordinates
Cartesian Coordinates

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Blender units and precision

In order to make blender units represent a real world unit it is necessary to assign a dimension size to the blender unit. When Blender first opens you are presented with the default cube measuring 2 blender units wide by 2 blender units deep by 2 blender units high. When importing a VRML or STL file into a rapid prototyping machine it is necessary to tell the software what dimension the units represent. So in order to manufacture an accurate 3D model in Blender and export it to a 3D printer or CNC machine, you need to know what the blender unit represents as a real world measurement.

The 3D world within Blender isn’t an unlimited space and there are restrictions as to how big a model can be. Size is limited by the available power and fall-off distance of the lights, the maximum clipping distance of the view camera and the maximum clipping distance of the render (output) camera. Complexity of a model is limited by the amount of vertices your system can handle. The more powerful a machine you have the more vertices you will be able to handle before the computer starts to lag behind the speed you can model at.

So how big should I make a blender unit?
If you were considering modeling a precision component or assembly, being able to model down to sub micron accuracy would be a distinct advantage. So if we consider one blender unit to equal one millimetre  how accurate can we get?
Blender allows you to numerically input the distance of  vertices to the precision of 4 decimal places (0.0000).  Say you extrude a vertex 0.0001mm along the X axis you have set its position 1/10th of a micron from the original. Pretty darn accurate and given that the best CNC machining centres can position to an accuracy of plus or minus 3 microns, you can model to a much greater accuracy than you could ever manufacture to. The draw back to this is your viewable work space will be limited to a
cube with 10 metre sides due to the clipping limit of the view camera, but unless you are designing a gantry mill to cut the wing spars for an Air-Bus A380 this shouldn't present a problem.





Putting Size into Perspective
  • The human hair is around 76 microns thick.
  • Most general purpose machine tools in skilled hands would be able to work within two thousands of an inch (50 microns)
  • The best CNC machining centres can position to an accuracy of plus or minus 3 micron, with repeatability of Plus or minus 1 micron.
  • A 100mm iron bar will expand 0.012mm with a rise in temperature of 10 degrees C
Microns
Positioning Accuracy





Other scales could be chosen for precision work such as 1 blender unit = 10mm giving a work area of 100 cubic metres, however this confuses the process and you constantly need to be aware of where the decimal point goes when you are entering extrude lengths etc.

For architectural designs it is common to use a scale of 1 blender unit = 1 metre allowing a viewable design space of 10 cubic kilometers and an accuracy of  0.1mm


Modeling in Blender

When blender first opens the view has a cube object in the centre. This is one of several primitive shapes available to you that can be altered to form your component. In Object Mode the shape appears as a solid cube and you are limited to being able to move its position within the global space, rotate it about a chosen point or scale the whole model. By pressing the Tab key you enter Edit Mode and the corners of the cube now have a yellow dot on them, connected by yellow edges. The yellow denotes the vertices are selected. In edit mode you can move the position of any selected vertices, add, join or delete vertices, fill the area between any three or four vertices with a face and much more to construct your model.

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Object Mode - Solid View

Cube (1) is selected with focus. If you press Tab this cube will become available to edit in edit mode.
Cube (2) Is selected.
Cube (3) is not selected
Object Mode - Solid View


Object Mode - Wire View

Cube (1) is selected with focus. 
Cube (2) Is selected.
Cube (3) is not selected.
Object Mode - Wire View


Edit Mode - Solid View

Cube (1) All vertices selected.
Cube (2) No vertices selected.
Cube (3) One vertex selected. Note the edges fade from yellow selected end to black deselected end.
Edit Mode - Solid View


Edit Mode - Wire View

Cube (1) All vertices selected.
Cube (2) No vertices selected.
Cube (3) One vertex selected 
Edit Mode - Wire View





Blender has a wealth of tools that allow you to model almost anything and these will be described in the following Precision Modelling tutorials. If you are new to 3D, work through the tutorials in sequence; drawing methods and the use of tools are introduced and described as the tutorials progress getting less detailed as your experience progresses. If you get stuck, simply go back through the tutorials to where the tool or method you are struggling with was introduced. The initial description of the process will be the most detailed and helpful.




The following  video tutorial covers some of the information above,
giving a brief description of Blenders interface.

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The following  video tutorial takes a look at a few of the commands
used in Object and Edit Mode

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