Model

Layer 1 contains most parts of the bulldozer body. Layer 2 contains the interior of the driver's cabin and layer 3 contains the track link pieces. The blend file has 1 group, containing the bulldozer and its parent but not the room and ground plane. To append only the bulldozer to another file simply append the bulldozer group to the new blend file. The headlights and tail lights have the emission material ready but it's not assigned to any faces. Simply enter edit mode and assign the material to the bulb faces or exterior faces of the glass to get emission. All parts are parented to the bulldozer empty arrow to allow easy moving and rotating.

Materials

All parts which have scratches have three materials on the material tab. The mix material is the one that is assigned to all faces. That material uses the other two materials (paint and metal), mixing them together as set by the mix amount texture. Most materials have three texture maps: diffuse, roughness(specular in Cycles) and bump. The same textures are used in both the paint and metal materials. The mix material uses one texture map: mix amount. Materials are set up for rendering with LuxRender 1.4. Things to note if you render with any other render engine:

• Obviously the materials will need to be redone. However almost all materials are textured so you should be able to set this up easily by mixing a glossy with a metal material using the mix amount texture. Materials which are not textured include: the interior (basic sandy color), window glass for windows and lights (slight cyan color for bulletproof glass) and the inside of the lights (aluminum metal preset).
• The glass in the windows and lights are modeled with thickness. If your render engine do not require this, simply delete the faces facing inwards.

Textures

The GIMP xcf files contains layer groups for easy editing and exporting of the textures. The layer groups are named according to their texture type. For example, ripper.xcf contains layer groups diffuse, bump, roughness and mix. To export the diffuse texture, simply hide all the other groups and export (File->Export as...) from GIMP as 'ripper diffuse.jpg'. The bump texture is exported as 'ripper bump.jpg'. All other layer groups follow the same method and all GIMP xcf files use the same layer organization and exporting file name: [GIMP file name] + [layer group name] + [jpg] Several layers are copies of the diffuse version of that layer and slightly edited afterwards. Example 1, the diffuse dirt layer: That layer is also used in the roughness group. The layer is duplicated (Layer->Duplicate Layer) and moved to the roughness layer group. It is then inverted (Colors->Invert) making the dark dirt brighter to get a higher roughness value (brighter = higher). Layer mode is then changed to Lighten only. Example 2, diffuse metal layer: That layer is used in the mix group as well. The layer is duplicated and moved to the mix group above the mix 1 layer. The mix material in Blender is set up to use black as the paint and white as metal. So the duplicated layer is changed to grey scale (Color->Desaturate) and contrast is increased (Colors->Brightness-Contrast) to get desired mixing amount.