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Back to Tutorials |
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Creating and Texturing a Gear - Part 3
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Using
Gimp to Create an Image Texture |
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For this part of the tutorial I will be using
Gimp 2.6 which can be freely downloaded from www.gimp.org
If you haven't used Gimp before its worth looking at the documentation
on the Gimp site because this tutorial will only cover the elements of
gimp necessary to create our material texture. If you are familiar
with a different graphics package you may be able to use that if it has
similar noise and motion blur filters. |
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When you open Gimp for the first time you
are
presented with an empty image window, the Toolbox and Layers dialogue
with tabs for Channels, Paths and Undo.
Gimp is very customisable so depending on the build you are using, you
may not have exactly the same dialogues available. You will need to
have the Toolbox, Layer and Paths dialogues open to do this tutorial.
Check the Gimp documentation if you need to alter any dialogues. |
We need to make a fairly detailed texture so we will need a large area
of image to work on. In the Empty Image Window menu click on
File>New. In the Create a new image dialogue that opens set
width
and height to 2400 and click OK. |
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A 2400 pixel square image will open with a white
background. Bump maps
in
Blender work in grey scale with black creating a raised surface, white
creating a depressed surface and 50% grey having no effect on the
surface. We need our background to be 50% grey.
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To set the back ground colour click
on the top black colour swatch in the Toolbox to open the Change
Foreground
Colour dialogue. |
Drag the Value slider V
to 50 or type 50 in the text box indicated and click OK. The foreground
colour will change to 50% grey
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Select the Bucket Fill Tool and with the cursor
over the image LMB click. The background will change to grey. |
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We now need to add a transparent layer over the
top of the background layer.
In
the Layers dialogue click the create new layer button (bottom left of
the dialogue) You can change the name of the layer to Radial if you
wish then click OK to add the new layer. The new layer will be created
and sit above the background layer in the layers dialogue. |
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To create the grain we can use a noise texture.
On the Image Window menu click Filter>Noise>RGB Noise to open the
RGB Noise dialogue.
Slide the Alpha slider over to 1 and press OK. The Radial Layer will be
filled with a fine noise texture. |
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To turn the noise into a radial grain pattern we can
use a radial motion blur
Click
on Filters>Blur>Motion Blur to open the dialogue. Change the Blur
Type to Radial. The Blur Centre should be on the centre of the layer.
Click OK to create the Blur. This is possibly a good time to make a cup
of tea as the process takes quite some time.
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We only need the radial blur to occupy 3/4 of the
image, because we need a linear grain for the gear teeth and bore.
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In the Toolbox click on the Scale Tool and
then click on the image. The scale dialogue will open. |
Set the scale type to percent and the width and height values to 75.
Click OK to scale the layer. |
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In
Blenders UV layout we have placed the side faces of the gear in the
bottom left of the layout so we need to move this layer into the bottom
left corner.
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In the Toolbox click on the Move Tool and
select move the active layer |
You
can now drag the radial blur to the bottom left corner. It helps to
zoom in and in Gimp you press Ctrl and zoom with the scroll wheel. |
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That's
the radial texture made and positioned within the image, we now
need to add a linear grain texture to the surrounding area.
Add another transparent layer following the same procedure we used
for the Radial layer.
Add a Noise Texture to this layer Filters>Noise>RGB Noise
with the same settings as the noise on the radial layer.
Add
a motion Blur to the noise on this layer Filters>Blur>Motion
Blur. This time set the noise type to Linear and set the length to
around 60 and angle to 90. Its worth experimenting with these settings
to get the grain pattern you require. Press OK and the noise will be
turned into a vertical linear grain pattern. |
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The
problem at the moment is the linear grain runs over the top of
radial grain, darkening and destroying the radial grain texture.
To overcome this we need to delete the linear grain from the radial
grain area of the image
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In the Toolbox click on the Rectangle
Select tool and drag a selection over the area of the radial grain. |
It
helps to zoom in Ctrl-SW moving the corner or side bars of the
selection with the LMB. When positioned accurately press the delete key
on you keyboard.
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We now have a finished metal texture to apply to our UV
layout. In
the Image Window menu click File>Save As and save the texture as
MetalTexture.jpg. In Gimp you need to add the file type (jpg) to file
name so Gimp knows what format to save the image as.
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In Part 4 we will adjust the UV Layout in Blender to
fit the image texture and set-up the materials for rendering.
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