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Back
to Tutorials |
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Getting
Started |
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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 |
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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.
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3D
View: Header Bar
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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. |
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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. |
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5)
Pivot Point
This
gives a choice of centre points for rotating and scaling the 3D models. |
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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. |
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Context Buttons
These change the control button options in
context with the operation you are performing.
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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. |
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Understanding
3D coordinates and Blenders 3D views |
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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. |
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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.
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The object centre coordinates of the blue cube in the
Cartesian coordinates diagram are displayed in the Transform Properties
window. |
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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. |
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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
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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 |
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Object
Mode - Wire View
Cube
(1) is selected with
focus.
Cube
(2) Is selected.
Cube
(3) is not selected. |
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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. |
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Edit
Mode - Wire View
Cube
(1) All vertices
selected.
Cube
(2) No vertices selected.
Cube
(3) One vertex selected |
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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.
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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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Tutorials |
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