MARI Texture Challenge - Breakdown

Since MARI was totally new to me I started with some basic tutorials. Thanks to Mike Jagodzinky and his nice Getting Started with MARI videos it was fairly easy to get going.

Texture Painting

I first started with basic colouring the diffuse channel. It was good practice to learn the different brushes, the paint buffer behaviour and most importantly the selection modes. These helped quite a lot to get the model textured.
The thing which I should have done to make my life easier here would have been to create dedicated selection sets in modo and then re-import the model as a new version.

After the base colouring of the bike and the pilot I started to add dirt and oil spills. For this I created several layers and at first a different channel for the pilot as well. But in the end I copied the layers of the pilot back to one diffuse channel just to keep it more tide and give my MacBook a not too hard time.

For the brushes I used only the presets which come with MARI.
My favourites here are:

• oldShipyard
• oldScuffs
• moleAttack
• looseEdge
• tRex

Combined with the really cool masking features like edge and fractal noise mask these brushes are really good and quick to use.

One thing I missed here a lot is that you do not have the ability to save the projection settings to a brush preset. Or at least save different presets for the projection settings. This would be a really nice feature to speed up some steps while painting.

The paint trough brush is also very handy and a bit similar to the painting in modo. I created some decals in Photoshop and a bump map for the suit.

Besides dirtying up the model I started to add corrosion and aberration with different mask layers. I then used these masks in the bump channel as linked layers. For the spec channel I imported the dirt layers as linked layers and added some correction nodes on top of these. First a desaturation node and then a layer to give it more contrast.

Base colour

Base colour with decals and markings

Scratches and abrasion

After some test exports I decided to export flattened channels out of MARI. This was the most efficient and fastest way to get going in modo.

Final Textures in MARI

modo Workflow

Painting the textures was one thing but how to utilise them in modo another. Since there were 26 textures for each channel I didn't want to set the offset for of them by hand. So this was a perfect way to practice my python skills for modo.

MARI Tools

I came up with a small KIT which allows me to import a bunch of textures and the script automatically sets the UV offset values according to the UDIMs in the texture name. Besides some other handy features it creates selection sets for each UDIM as well. This makes selecting and creating different material masks much easier.

MARI Tools for importing textures into modo

You can download the current version at the Foundry modo forums.

Shader Tree

Once the script was done I started to think of a good and effective way to set up my shader tree. In the end I have three main groups containing the textures: diffuse, bump and specular. At the beginning I separated the dirt layer from the diffuse colour and layered it on top of the materials. But this was very ineffective speaking of render times. So I exported it directly flat into the diffuse map and used the specular textures to control the reflectivity.

The marked groups only contain the textures. "SPEC_AND_TRANS" are the specular textures and instances of these set to transparency amount. Both texture pairs are set to multiply so that these only affect values which are actually in use.
The "PRIMING" group are the diffuse textures but set to alpha only and acting as a group mask. Inside are three different materials for the priming colour layer. So basically this layer mimics the grounding underneath a car paint or as for the pilot scraped leather.

Speaking of reflectivity, I am a big fan of physically based shading. I always start with a material with "Match Specular" on. The car (or in that case the bike) paint is a good example of how my workflow is. But before that two more important things to switch off is the "Affect specular" in all the light materials and to deactivate simple shading for the lights.

Shader Breakdown

With that set up I start tweaking my material. To control the reflectivity I tend to use a gradient. This gives me great control how the fresnel effect should appear of each material. To start with I set the min value of the gradient to 0.02 and the max value to 0.98. I tweak the curve to look like shown in the image below to start with.

I set the gradient to multiply and in the underneath lying material I set the specular value to 1.0 (100%). With that I can quickly adjust the overall reflectivity instead of adjusting the gradient curve. Also I am able to use one gradient on top of different materials if I like.
As you can see I try to start with a preset scene to create a material. Instead of using the original textures I first setup my material with some dummy procedural textures. These are then replaced by textures in the final scene. This process renders much quicker and I can easily test out stuff.
Next are some scuffs and dents. These consist off two layers. The first is the PRIMING layer and the second a bump layer. In the priming group is a high contrast noise texture and a matt chrome material to mimic the underlying metal of the paint layer. The noise texture is acting as a group mask. I instanced this texture into the SCUFFS group and set it to bump.

Scuffs & Bumps

Next I added some fine scratches which you always find on a clear coat. This breaks up the surface and makes it look more natural.

Fine Scratches

I created three noise textures. These are identical except the rotation. All three noise textures are multiplied over the specular amount.

With these noise maps I am able to adjust the effect very quickly in size and strength in the final scene.

After the scratches I multiplied a fine and smooth noise texture over the bump texture. This simulates a so called orange peel effect and breaks up the reflections on a paint material even further.

Orange Peel Effect

You can barley notice this effect but it's the little things that make the difference.

For the last part there is the dirt layer. For the diffuse colour I took again a noise texture with two dark brown colours to map it on top of the material colour I created a second noise and used it as a layer mask (inverted on) for the dirt noise.

I then copied this layer mask noise to the DIRT group above in the shader tree. Here I adjusted the contrast a bit more and changed the the effect to specular amount and the blending mode to multiply.

After I am done with setting up my preset material I copy it over to my work scene. Here I exchange the dummy noise maps with the real textures. 

The only noise maps I keep are the orange peel and the scratches. Of course I needed to adjust the structure a bit.

As you can see I used only one gradient to control the materials of the bike. Chrome and aluminium are on top of it since these two shouldn't be affected by it.

I used a similar approach if I had materials which shouldn't be affected by the diffuse textures (e.g. glass for the windshield or some chrome parts).

Lighting was not really special. Two area lights and a studio HDR. Because it was a texture challenge I decided against a background and motion in the image.

The beauty looked almost good enough. For post I went into Lightroom for some image adjustments. After adding some grain I exported it to Photoshop and applied a small amount of colour fringing (chromatic aberration) with the lens correction filter.

And that's it. You can see the final image here.