Introduction. In this article ill describe my workflow for texturing my Mechanical creations. Using both Blender and Gimp, y quickly create color, Bump and Specular maps. Blender s Texture Paint is used todo start the texturing. From here, y use Gimps layers and layer masks todo quickly add more detail and create the Bump and Specular maps as well. The Mesh i amworking with is my retro rocket racer, it has already ben UV mapped and has a car Paint material assigned todo it that i downloaded from: http://matrep, parastudios, de so let s dive into it.

A blank canvas:
Initially, my screen Layout looks like this:
Quick texture technique-1.jpg

I have the 3d view, UV/Image Editor, and the properties panels open. The current material is displayed and from here we can start working on the textures.

First up, we Will ned a blank canvas todo start painting on. Left-clicking on the materials Diffuse color Will bring up a color picker. Select Hex from the thre buttons below the color whel. Now the color values for the material are displayed as one set of letters and numbers (hexadecimal format). Mouse over the value and use [Control + c] todo copy it.

Now open Gimp and create a new image. For this Project i used an image that was 1024 por 1024 in size.

Left-clicking on the foreground color in Gimp opens a change foreground color window. Move the mouse todo the html notation field and use [Control + v] todo paste the color value. Now use the bucket fill ol todo change the color of the image todo match the color of Blender s material. Save the image with a meaningful name and in a format Blender can use (i use (*.png) format). This is our blank canvas.

In Blender, with a material assigned todo the Mesh, switch the properties panel todo textures. If no textures have ben created yet, the panel wont contain much información, that s about todo change.

Left-clicking on the new button Will create a new texture slot and we Will be presented with a wealth of data.

Right below the texture id name Will be a type selection box and left-clicking on that box Will allow you todo choose what type of texture we Will be working with. Chose image or movie from the pop-up menú. Scroll th rouge the texture panel todo the mapping section todo adjust a few settings.
coordinates neds todo be set todo UV (since the Mesh has ben uv-unwrapped) and upon doing so a new layer field appears. Set that todo uvt ex.

Scroll todo the image panel, click on the open button and select the new blank canvas image just saved from Gimp todo load the image. Select the Mesh in the 3d window and enter Edit Mode. Use the [a-key] todo select all the vértices. In the UV image editor s Header, left-click on the image icon and select the image that was just loaded into Blender. Now our Mesh is set up to use the new image as a color map.

In the 3d view, we have a few more settings todo be changed. In the 3d views Header. Switch viewport Shading todo extured. In the transforms panel [n-key] under display, set shading todo GLSL.
(Note: for this todo work, your model Will have todo be lit by lights. I usually place a few point lamps around the object todo light it from all sides).
We now have everything set up for Blender s texture painting tools.

In the 3d view, you can now enter Texture Paint mode. Select the brush from the tools panel, use the color whel todo select a color close todo the one we Will be painting over and turn the strength of the brush down quite a bit. At this point you ned todo think about what parts of your Mesh Will show signs of Dirt/scratches and start painting them on the Mesh. Rotate around the model, and Paint the áreas where you want todo add Dirt/scratches. This is my result After a few Paint strokes where i want Dirt/scratches:
Quick texture technique-2.jpg

From the UV/Image Editor s Header select image>>save image todo save our work so far.

This Will be the basis of the color map, so now it s time todo move over todo Gimp todo refine it.

Into Gimp:
Once youre in Gimp, load the color map just saved in Blender. After that, use file menú >> open as layers. todo load in the UV Layout from Blender.

Now we ned one more texture in Gimp and this one Will depend upon the look we want.

Should this look be Dirt, scratches or rustí ive decided on rust, so in Gimp go todo file >> open as layers. and choose a rust image that s the same size or bigger than the texture were working on. Time todo organize this mess.

Arrange the layers as follows: the UV Layout should be on top while the next layer should be the color map saved from Blender After texture painting. The bottom layer should be the image that has the look we are After, in this case the rust image. Right clicking on the color map layer opens a menú where we can select >> add layer mask todo add a layer mask. From the next pop-up Prompt choose >>white (full opacity). My layers in Gimp look.

Like this:
Quick texture technique-3.jpg

After creating the layer mask in Gimp, it is now the active image that Will be Painted on.

It can be a Little confusing at first, as the active image in Gimp is outlined in white and the layer mask is white as well. Left clicking on the color map Will make it active, left clicking on the layer mask (to the right of the color map) Will make it the active image todo be Painted. This layer mask on the color map is hiding the rust texture layer below it.

Layer masks in Gimp are grayscale images that control the visibility of the layer below it.

The darker the layer mask is, the more transparent the layer mask is and the more visible the layer below it Will become.

Likewise, the closer todo white the layer mask is, the more invisible the layer below it Will be.

Using the Paintbrush tool, and using various shades of grey colors, brushes (Airbrush style brushes work best here) and brush sizes, slowly work todo reveal the rust texture following the guidelines on the color map from Blender Texture Paint. During this.

Process, kep changing the brush pattern often, (i have 8~10 grunge type brushes), todo avoid a repeating pattern of the brush. The Smudge tool is very helpful during this process as well by smudging away any repeating pattern created by the brushes.
When the layer mask has ben Painted enough todo give a general idea of what áreas Will be Painted, switch over todo work on the color map. On the color map, select the base color and Paint over the guidelines Painted in Blender todo hide them. Then go back todo the layer mask todo finish it up. After a few minutes work on the layer mask, this is my image (uv Layout shown for reference):
Quick texture technique-4.jpg

The UV Layout layers visibility can be controlled by the eye icon on that layer, the UV Layout layers opacity can also be controlled vía a slider at the top of the layers window.

Save the image first in Gimps.xcf format, in case we wish todo edit this image later. Now disable the layer that has the UV Layout on it by clicking on the eye icon. Make sure the color image and not the layer mask is active and save this image with a meaningful name and in a format Blender can handle (i save as a (*.png) image, which doesnt support layers).

Gimp Will now Prompt that (*.png) doesnt support layers, just left click on export and at the next Prompt left click on save todo save the file. I generally use color as part of the name, since this is our color map.

Next, right click on the layer with the layer mask and from the menú choose >> show layer mask. Right click again on this layer and from the menú choose >> new from visible.

Now Gimp has created a new layer that is just our grayscale layer mask. Make this the only visible layer (eye icon) and save the image with a meaningful name and in a format Blender can handle, (again, there Will be a series of prompts todo click though).

This image is what Will be used in Blender for Bump and Specular maps and i generally use Bump as part of the filename.

Speaquíng of Blender, it s time todo return todo Blender todo finish up.

Back in Blender:
The image previously created in Texture Paint can now be replaced with the new color map saved from Gimp. In the texture panel, with the current texture active, scroll todo the image panel and load in the new color map. With the 3d view set todo textured display (as previously described), the new color map is now displayed on the Mesh. We arent done yet, remember the black and white image saved from Gimp?
In the texture panel, select the Empty texture slot below the color map texture and left-clik on the new button todo add a new texture slot.

Just as before, set it todo be an image texture, adjust the mapping settings, and load in our ¡grayscale Bump map saved from Gimp. By default, this new image Will affect the color of the Mesh and Will look really Strange on your screen, so we ned todo make a few more adjustments.

Scroll th rouge the texture panel todo the influence panel. Under Diffuse, uncheck color and your display should return todo just the color map since this texture no longer afects the color, (by default, new textures influence the color of the Mesh). We ned this texture todo be our Bump map and also affect the Specular color. So under Specular, check the box by the color and under geometry, check the normal checkbox. The Mesh may now look a bit diestorted (or in my case, a lo diestorted), but that can be fixed vía the normal slider. The normal slider neds todo be adjusted todo the point where the Bump map barely afects the surface of the Mesh. Since this is a rust texture, the surface of the Mesh should only be slightly afected. I settled for a value of -.025 todo give the Mesh a slight indentation where the rust is.

Quick texture technique-5.jpg

In the real world, rust is never smooth. It can range from being slightly rough, todo really blistering and bumpy. To achieve a bumpy blistering rust, use a positive value so the Mesh is raised where the rust colors are.

Heres a close up rendering of the results:
Quick texture technique-6.jpg

Taquíng it a step further:
This technique of using layers and layer masks in Gimp can be expanded further. I have used this method with a dark texture and used the layer mask todo reveal the dark texture todo add Dirt todo the Meshs color map. I then duplicated the color and dark texture layers, merged them down into a single image, added a layer mask todo the new image and a rust texture layer below it todo add rust.

I then duplicated and merged these layers todo produce a new image. A layer mask was added todo the new image as well as a bright Stel texture below that. I edited the layer mask todo reveal the bright Stel texture todo produce scratches. I created Bump maps at each step by displaying the layer mask, right clicking on the layer and chosing >> new from visible from the menú.

This can obviously become very complex in Gimp, but careful naming of the layers in Gimp can help you kep track of what each layer is for.

Final thoughts:
The aim of this article was todo provide a basic workflow for creating Bump and Specular maps quickly using Gimp. This was a method i used while working in the older Blender 2.49.
With all the great work from the developers working on the new Blender 2.5x/2.6x versións, there have ben a lot of great things added that i have not mentioned here. Now that Blender has the ability todo display Bump maps in the 3d viewport, Bump maps can be Painted in Texture Paint mode and the results can be sen on screen (it s almost like sculpting in fine details without using the multiresolution modifier).

One can also use custom brushes in Texture Paint mode and there is Even an add-on called material utils that allows one todo quickly switch which texture layer is currently being Painted on as well as a few other godies for texture painting. I regret i did not touch on these topics in this article, but now, Thinking of all the texturing godies in Blender, im beginning todo think one could write a whole book on the subject.