Weathering .

Before we go on, we have to understand the effects of the weather and time on our spaceship. There are basicly 5 different types of dirt and waethering effects that we have to consider: 1) Dust. Any colour, usually dull, it settles everywhere there's a reeceeding. 2) Rust. Orange to brown to red, dull and settles between hull plates, tubes and everything that carries-gets in contact to corroding agents. 3) Smoke. Any dark colour. Positioned near the engines, and airvents. 4) Oil spots and various. Basicly everywhere. 5) weathered paint, scratches, damage. Mainly over sharp edges, it can be determined by the overall movement of the spaceship and friction with atmosphere, micrometeorites, so on. To recreate dust (we'll just settle with dust for this tutorial, ignoring Rust and smoke) I duplicated the orange material I already have and tweaked it until it was dull and brownish. For the sake of detail I've also changed the main texture to the more rusted dusty one. For the weathered paint material I opted for something similar to white, but with a higer level of shininess.

The masks

It is time to look at your model and choose the mapping method for your mask. For the crok I wanted to have the main two colours as the base layer and then the white stripes on top. In order to do that I created a first mask which described the boundaries of the gray and the orange materials. Then I created another mask to create the white stripes and a third for the top decals. The weathering follows the same rule as the other materials, and is composed of two materials (one for dust, the other for scratches) and two masks. Since the colour banding for the crock is basicly following an horizontal scheme, and the shape of the spaceship itself follows a vertical scheme, I opted to use planar mapping for both the base colouring and the weathering effects. Here comes handy the untextured scene we saved before: Now that we know more or less the materials we want to apply and the mapping methods we want to use, it is useful to create a few renderings of the untextured model for reference and baselayer for the masks. Since I needed to create a planar map I set a camera on the right side of the model and took a snapshot of that. I also do the same with every single group I created in the previous stage. The next step is to create with the same method a viable dirt map to use as a base for our dirt masks. In order to do that I placed several lights with soft blurred shadowsthat helped identify the receeded parts.

To create the weathered mask I created a strong light point over the front to give the edges the torn out appearance. We can now import all the renders into a paint program that supports layers (Photoshop or the Gimp to name two) and create a layered file with all our different masks. After drawing a 2 colors mask for the color banding I decided to create the white map using the textures from the cd and importing some of them into the paint program. Be careful not to insert writings and logos that are not simmetrical: these objects should be superimposed over another mask, to be sure that you don't have a mirrored image if you use the same mask for the other side.

Then the dirt mask needed some tweaking in order to be used, therefore I applied some noise and a Gaussian Blur over the whole image. Same thing applies to the weathered mask; remember that we're dealing with BASE textures, do not expect this method to produce final results for both dirt and weathered masks which, as we'll see later on, should be customized more by hand.

It's now time to create the materials and apply them to the object. We start with the base material which I decided to be the gray one. Then I added the orange one over it, using the mask I prepared to filter out transparent areas. On top of that goes the white material with it's striped mask. Note that the white mask is itself a composition of two masks: one later and one top map each one mapped with a different channel. This sandwich of materials is the base colour of the spaceship. There's one nice side effect into all of this, since I've used the same planar mapping for color, dirt and weathered materials, I can add later on more layers into the mixture, adding new custom details to each of the masks using the same channel. It's now time to add dirt and weathering to the composition, using the respective masks. The result is ONE multilayered material that serves all. The bad news is that some 3dapps tend to be a little sluggish when dealing with such a complex material. The good news is that by tweaking the output of the single masks into the 3d application itself you can give your spaceship more dirt, or change the colors indipendenlty or eliminate the weather effect without the need of entering the paint program again.