Texture an authentically worn K-2SO droid

In this tutorial we’ll be texturing and rendering K-2SO from Star Wars: Rogue One. We will focus on texturing the droid using Substance Painter to make him fit into the Star Wars universe; slightly reflective, yet dull and worn for that truly lived-in appearance. This will be broken down by surface damage, scratches, micro-noise and the roughness properties of the robot’s surfaces, with a final layer of grime to build up depth like a true Star Wars prop.

Finally, we will output everything for rendering in KeyShot for that advertising poster look. The model has been built in quads using subdivided surfaces, so it can be smoothed at render time using the surface normals of the mesh.

Download the files you’ll need for this tutorial and the accompanying video.

01. Initial setup

Download and import the model into Substance Painter

Download the model and you should find that it’s ready for importing straight into Substance Painter. This has been set up for a VFX production pipeline in mind. We will render in KeyShot and use the surface normals of the geometry with multiple textures per component. On importing into Painter, shaders are applied to each respective model part that require their own texture. To select the model parts use the Texture Set List window. UDIM’s are not used since KeyShot does not support them.

02. Blocking in: smart material presets 

Quickly block in materials using Painter’s presets

Using the presets that come with Painter, quickly block in the values and materials of the droid. Use Steel Gun metal that ships with Painter, and place this onto the model as a starting point, masking appropriately for the light trim and elbow joints by using the polygon fill tool, shortcut key [#4]. ZBrush is also used to create ID maps on the fly as and when required.

03. Building up the damage in layers and metal blemishes

Inspect and replace the preset layers with custom layers

Although the smart presets serve as a good starting point, the layers are inspected one-by-one and replaced with custom layers better suited to this project as we want a custom appearance. The dark metal material properties of K2 are broken down into three categories; (Colours above are exaggerated in the images for clarity). Metal colour/roughness variety – In effect this is procedural noise to create a variety of metal blemishes all over the surface to make the surface appear more worn and even sun damaged. The roughness channel is tinted to help alter the light absorption.

04. Micro scratches

Add scratches to subtly break up the surface highlights

Next we want to add some scratches to give the droid a more used look. Create a new fill layer, mask it and then apply an MG Mask builder with a stock Grunge texture to Image Input #1 to apply scratches. Manipulate and balance to your liking by using the exposed sliders. With this layer, we are aiming to subtly help break up the surface highlights.

05. Paint surface scrapes

Use the MG Mask builder surface to paint surface scrapes

Again, use the MG Mask builder surface to create variety, for example, you could make it appear that the paint has worn off or picked up other coloured abrasions by K2 interacting with an environment. At this point, the metal texture is tinted to again add texture variety. Strengthen the idea that this droid has been around by adding deep battle damage: my approaches are shown on the accompanying video walkthrough.

06. Deep battle damage 

You can either add battle scars by hand or by using generators

Battle scars can be done by hand and/or by using generators. There are two approaches that are demonstrated by video. Ultimately ensure the diffuse fill layer is white with some opacity; this is the paint primer. The height channel for this layer is tinted darker so we can carve the scratches nice and deep. If they are not sharp enough, add a sharpen filter to the layer by right-clicking for that freshly sheared appearance.

07. Copy and paste 

Copy and paste your material data to the other nodes

Now it’s time to copy our material data across to the other nodes. To do so, group all your layers and name them appropriately, then right-click and create a Smart material. It will appear in your shelf ready to be used on the other components. By focusing on each component as we have done so far for the head, we can achieve the same level of detail for our other texture sets.

08. Dirt and grime for that weathered look

Paint in dirt and grime with a Dirt 1 brush

Finally, a custom dirt/residue pass is completed across the model. This could be done using the particle brush system, but I feel like I get too amazed by watching it and have more control this way. Apply a fill layer and paint in a dark value with the Dirt 1 brush, around areas where it would collect. By applying an alpha to this layer and changing the brush alpha to Drips, this layer is then customised further with weathering streaks. Since Dirt is not reflective, its roughness is made white and metalness is turned to zero.

09. The imperial icing

Add the rebel alliance emblem to K-2SO’s shoulder plate

For the grand finale, we now get to add that rebel logo on the shoulder plate! Drag the logo provided into your texture shelf. Whilst in brush mode apply the decal as a stencil to your brush by dragging it into your stencil slot. You should see it immediately tile across your screen. Press the S key, a gizmo will appear and with the Alt key and MMB you can move the stencil to your chosen position and scale with RMB.

10. Emblem integration 

Work on the emblem to give it a more worn appearance

Rather than blocking in the decal 100 per cent as if it was brand new, I use a standard layer and the Crystal brush; as it has some noise in its alpha, from the outset I can give the emblem a worn appearance. To finish using the stencil, hit the X next to the brushes Stencil slot. To bed the decal into the metal surface I then apply a Surface Worn Smart Mask and alter the MG Mask Editor’s Generator parameters to my liking. Roughness is then increased to break surface highlights by adding a level to only affect this channel.

Next page: Find out how to finish off your design

11. Keyshot preparation

Export your textures from Painter

The textures are exported from Painter using the KeyShot present configuration for Diffuse, Roughness, Height and Metallic. Before we take everything into KeyShot, subdivide your meshes until the geometry smoothens to your liking, whilst ensuring Smooth UV is not active under the ‘Tools > Geometry’ menu. Remember, every subtool also needs to have a unique name as duplicates will not export. 

12. Material preparation 

Take care when preparing your materials

In ZBrush the diffuse textures are applied to the meshes in their texture map slot. This is done so UVs are sent with the model to KeyShot. Be mindful that between sessions, the KeyShot bridge may wipe over the materials you’ve set up if you change a subtool name, for instance. So, try not to rename subtools and keep everything as consistent as possible to prevent this. As a failsafe, get into the habit of saving your materials in a folder.

13. Material focus

Pay special attention to setting up the head’s material properties

The head is isolated, since it has a large variety of forms, which allows me to focus and tweak its material properties. Using a metal shader, the rest of the textures are brought in and assigned one by one. Diffuse goes into Colour, Roughness goes into Roughness, Height goes into Bump. Spend some time adjusting the roughness texture brightness and contrast sliders to fine-tune to the desired look.

14. Perturb the surface 

Add a subtle grain to the model with a noise texture

To further enhance that metal feeling, a subtle grain is added to the model by layering in a simple noise texture. Using a Bump Add utility in KeyShot, the Chest height map is assigned along with the supplied Metal_Noise_Bump. Be sure to untick Sync on this texture so you can change the mapping to Box Map. Adjust the Bump Add ratio slider and texture intensities to your liking to balance the damage scrapes with this texture.

15. Advance material tuning 

Fine-tune your material then duplicate it

Finally, labels are used and our roughness textures are layered into our material again to provide more control over the grimy appearance. Once you’re happy with this material setup, we can then duplicate this shader and roll it out to the other components for consistency and assign their respective textures.

16. Create a sandstorm effect

Build up sand deposits across the model’s panel crevices

In Painter add a white fill layer with a mask and a Mask Builder Generator. Add a custom grunge texture such as Dirt 1, reduce the default grunge value to your liking and use the AO slider to build up sand deposits in the panel crevices. Increase the layer’s roughness, add some height and apply a Sharpen filter. 

17. Keyshot dust label 

Add a diffuse material type label to your shader in KeyShot

Back in KeyShot, a ‘diffuse material type’ is added as a label to my shader with a sand RGB colour value. Within the material graph, I import the new textures and assign the base colour texture as the opacity mask, adding the height map into the bump channel for extra definition. You can develop the look further from here. 

This article originally appeared in 3D World issue 216; buy it here!

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