Getting dirty

Often it’s the small details like scratches, scuff marks and dents that lend a certain realism to even the most fantastic objects. In fact, the everyday wear and tear that can only be re-created with a careful mix of hand-painted textures and photographic reference can be the thing that really makes or breaks a model.

In this tutorial, we’re going to take an otherwise pristine droid and give it a good visual thrashing. Imagine it is battle-scarred from years of conflict and abuse: we need to create the tell-tale signs of everyday life. Its edges are faded and worn, scratches in exposed areas have been filled with ground in dirt, and recessed areas have become clogged up and decals have decayed over time.

It is often these touches that can make your model shine, adding character to an otherwise lifeless object. And knowing where the scratches, grazes and grime will be most effective can be an artform in itself.

Using scene files available here, we will begin by using the Render to Texture dialog to render an Ambient Occlusion (MR) map. This is used throughout the texturing process, both as an aid in knowing where to paint (and where not to) and as a mask for filling new layers. This map can be multiplied above the texture, offering free ambient occlusion without any extra render overhead. It’s a technique commonly used in game texturing, where real-time ambient occlusion would be too expensive to use otherwise. We will also look into using a scratch brush to roughen up the edges of the model. While the brush itself is important, painting these scratches should be done in a very loose fashion, as if you were roughly scribbling on paper.

We will create a base texture, followed by colour fills that use the Use All Layers function in Photoshop, an often overlooked feature that can quickly and effectively add much-needed variation to a texture.

Finally, we’ll create a greyscale bump and reflection/specular map using a modified version of the colour texture. Layers and the blending options in Photoshop will help us create a hard-surface texture that looks like it’s seen many years of use, and interacts with lighting and shaders as you’d expect an object to in the real world.