3D Computer Graphics Using Blender 2.80 - Modelling Methods, Principles & Practice

          Blender Tutorials: Machined Metal Gear- part 3

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Creating and Texturing a Gear - Part 3

Using Gimp to Create an Image Texture

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.

Gimp Dialogues 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.

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.

Forground Colour 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
Colour Picker
Bucket Fill Select the Bucket Fill Tool and with the cursor over the image LMB click. The background will change to grey.

New Layer 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.

Add Noise 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.
Noise added to layer

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.
Blur Dialogue
Radial Blur

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.

Scale Button 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.
Scale Dialogue

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.

Move Button 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.

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.
Linear Blur

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

Select Tool 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.

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.

Completed Texture

In Part 4 we will adjust the UV Layout in Blender to fit the image texture and set-up the materials for rendering.

<< Gear Part 2 UV Unwrap
Gear Part 4 Image Texture >>

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