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Back to Tutorials |
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Creating and Texturing a Gear - Part 1
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Following on from the Precision Modelling
Guide, which walked you
through the basics of producing dimensionally accurate models and
outputting them to scaled dimensioned drawings. I thought it would be
good to describe the process of turning those 3D representations into
an almost photo realistic image, suitable for use in technical or
marketting literature.
This won't be an in depth guide to
modelling, thats already covered in the Precision Modelling Guide and I
am assuming you have already looked over those tutorials before
starting this. |
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The process of
creating
the geometry of a gear is quite complicated and if done manually will
require quite a bit of maths, fortunately for Blender
users, there is
an
excellent add on script created by Stefano
Sellery called Blender
Mechanical Gears, that does all the hard work for us.
If you
haven't come across Blender Mechanical Gears before you will find there
are two scripts, the first called BMGm-0.0.2.py generates a mesh of a
gear tooth to the
peramiters you set, the second BMGs-0.0.2.py allows you to animate the
rotation of
the gears so they spin in perfect mesh. For this tutorial we will only
be using the mesh script.
If you havent already got it the script can
be downloaded from the Blender Wiki. Contained in the zip
file is the two scripts and an excellent .pdf manual. You will need to
put the scripts into your Blender scripts folder. All the instructions
for doing this are in the BMG manual. |
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Once
you have
loaded the BMG scripts go into Blender and split the 3D view into two
screens and change one of them to a script window. On the scripts menue
ckick Scripts>Mesh>Blender Mechanical Gears. If
Blender was
already open when you added the scripts to the script folder
the
scrip won't be showing in the list of available Mesh scripts so click
Scripts>Update Menues, then try again.
The BMG interface will open in the Scripts Window which contains a lot
of options for different gear types, the BMG Manual contains all the
information on how to setup different gear profiles. For this tutorial
we only need to have a basic gear shape so the default settings shown
opposite will
suffice. |
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If
you click generate the script will create two gear teeth, the main gear
centred on the scenes origin (located at 0,0,0) and a pinion tooth
perfectly meshed to it.
We don't need the pinion and could have clicked No Pinion in the BMG
interface, so select the pinion and delete it.
The
object centre of the teeth are on the centre axis of the gear allowing
us to snap the cursor to the centre point and Spin Dupe the tooth
profile around the centre point. |
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The
tooth has a pitch circle radius of 5 Blender units and we need to add a
bore of 2 blender units diameter (it makes sence for one Blender unit
to equal one centimetre on this project)
If you Tab
into edit mode you will see the geometry of the tooth, the inner
diameter is constructed of 4 vertices (A) which need to be joined to
the bore of the gear and the tooth has an unnecessary edge loop running
horizontally through it (B).
Alt select and delete X
Edge Loop the unnecessary edge loop(B).
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1.
With the cursor on the object centre and in top view add a circle with
60 vertices ( 20
tooth gear x 3 vertices = 60)
2. In front view, raise the circle 0.5 Blender units to align it with
the top face of
the gear
3.
Delete all the unnecessary vertices from the inner diameter, then
select the 4 inner vertices on the top of the gear tooth and the 4
inner diameter vertices.
4. Add feces between the selected loops F Skin Face/Edge
loops
Ctrl-R
to add a loop of vertives and slide them to point (A)
Ctrl-R
between the new vertices and the original gear tooth vertices and press
number 5 on
the keyboard (not Num Pad) to add 5 more evenly spaced loops that will
make up the gear recess (B). |
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Copy Shift-D
the new vertices
from the top face of the gear and snap them to the bottom face using
Blenders Magnet Snap feature (on the 3D view headder) set to Closest
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| Select
the vertices on the inside
diameter and F
skin new faces |
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default setting of 1 Blender unit for the thickness of the gear is a
little thin for our purposees, so increase the thickness of the gear to
3 Blender units. To do this Box
select all the vertices on the top half of the gear and move them G in the Z axis 1 Blender unit. Then
deselect All, Box
select the bottom vertices and move these G Z -1 |
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To complete the tooth segment we need to
add the top and bottom face recess.
To do this Alt-RMB
the top centre vertex loop then Shift-Alt-RMB
select the coresponding loop on the bottom face.
Turn on Proportional Edit on on the 3D view headder and set it to
Sphere Falloff.
Scale
the vertices on the Z
axis and adjust the proportional edit influence with the mouse scroll
wheel until you achieve a similar result to this. |
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In top view Tab
into Object Mode
and snap the cursor to the Object Centre Shift-S
Cursor->Selection then Tab
back into Edit Mode.
In the Mesh Tools panel set Degr:360 and Step:20 and press Spin Dup.
The 20 tooth gear will be generated.
Select All
and Remove Doubles W,
then Set Smooth W.
Press Ctrl-N
to recalculate the normals to the outside.
In the Modifiers panel click Add Modifier and choose EdgeSplit with the
default settings.
Having the triangular faces on the top and bottom face of the gears Set
Smooth,
will cause some shading problems so in front view Box select the top
most vertices and Set Solid W.
Repeat this for the vertices on the
bottom face of the gear.
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That almost
completes gear model, all thats now left to do is add the keyway into
the bore.
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With the cursor on the object centre, in
Edit Mode and Top View add a Plane and scale it by 0.2
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Move G
the plane on the Y
axis 1
Blender unit
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Select All
and use the Knife
tool to cut new vertices for the keyway using the vertices of the Plane
as a cutting reference to snap to. You will need to realign the corner
vertices onto the vertices of the plane. This can be done precisely by
snapping the cursor to the corner of the Plane and scailing the corner
vertices on the X-Y plane (Shift-Z) to the cursor, with the Pivot set
to 3D Cursor.
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Once you have cut the keyway profile,
remake the missing faces. |
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That
completes modelling the gear. If you haven't already saved it now is a
good time to do so. You should also give the gear a meaningfull name in
the Link and Materials Panel.
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In the next section we will be unwrapping the
gear into a two dimensional UV layout ready to apply some image
textures.
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