Making of Monster Car
Glenn Melenhorst shares his workflow for the adorable Monster Car
Several of my friends had purchased 3D printers and said they would gladly print a character for me if I'd like. Though I work digitally every day, I hadn't used ZBrush for a long time. It was the perfect reason to open it up and come to grips with all the updated workflows I had not been paying attention to.
Step 01: The car
I don't know why I decided on a big monster in a little car. I had a very low-detailed (heavily triangulated) BMW Isetta model lying around from years ago which I wanted to re-model in Quads in Blender. I pretty much distorted it into shape with a lattice in Blender, then threw the whole thing away and used the body as a basis for retopology. The rest of the car was modeled piece by piece in Blender.
Step 02: Car materials
I rendered live in Blender's viewport using Cycles to check my car paint shaders and chrome, etc., trying out different schemes dynamically which was really great. I could also swap out different HDR images and lighting setups and see them update in real time. I kept the palette simple, limiting the colors and sticking to muted tones, popping to brighter colors here and there.
Step 03: The monster
The monster started life as a sphere (and he still pretty much looks like one now) in ZBrush. I pushed and pulled it about using the Move and Clay Build Up brushes until I found a form that started to look good to me. I also used DynaMesh to keep adding faces and detail to the model as I sculpted. The car was imported as an OBJ to indicate the volume I had to play with. Initially simple shapes indicated hands, hat, eyes, etc. and were soon bent into shape and refined until they were ready to export as OBJs back into Blender for posing.
Step 04: Rigging
Here I was back in Blender, where setting up a rig was a very simple matter. I normally use B-bones, which can be subdivided into bendy spline-like bones (great for the tentacle on the back of the car). I could have posed him in ZBrush but Blender is easier. As you can see, I used the bare minimum of setup and it took all of 10 minutes to get him posing. Bone heat in Blender (automatic weights) is about as good as I've seen for skin weighting. I posed the character and, using Transpose Master in ZBrush, bought the posed character back in and passed the pose through to each SubTool automatically.
Step 05: Retopology
I attacked the tentacle and hood ornament the same way as the monster. The tentacle was made by building a sucker shape in ZBrush from a sphere and converting it to a mesh insert brush. The process was easier than I thought. Then I had a brush that could stamp down as many suckers as I needed. If I was to build this as a low poly mesh using subdivision surfaces, I could have never achieved this level of randomness. The resulting mesh was too large to work with, so a simple click of a button, in this case ZRemesher and I ended up with a perfect low-poly tentacle ready to rig with B-bones in Blender.
Step 06: PolyPaint
While I had the low-poly monster (and tentacle) in Blender, I marked some seams and unwrapped them, ready for texture. Once back in ZBrush, I used PolyPaint to rapidly color the character, creating diffuse, Specular and displacement maps. These I converted from PolyPaint to texture maps in ZBrush, flipped them vertically in Photoshop, and built materials in cycles using them. (No idea why ZBrush is the only app to put maps out upside down - I know there is a preset to change this but I must be too lazy. ;)) The monster is largely a big subsurface jelly bean which added enormously to the render times.
Step 07: Lighting
Rather than build a room and environment for the car, I built a floor and two walls as a stage which I subdivided and smoothed . Beyond that, I set up a HDR background (there are plenty on the net for free) and Image Based Lighting, which provides both a light source and reflection map which adds a realism to your work that is worth the effort. I played around a bit here, trying different images and lighting configurations, settling on a single light-emitting rectangle and the HDR seen in this image.
Step 08: Adding bits!
The bits, the part of the job I like the most. This part can take days and finishes when I get bored. It is adding little details, stickers on boxes and windows, decals, little batwing ornaments, autumn leaves, pens in pockets, braces, locks, and straps.
I really like this bit as it starts to tell the story more completely. I used a fluid system in Blender to make the slime from the tail pipe (A), Photoshop for the registration stickers (B and C), and played around with simple sculpting in Blender to find a happy glass lens look for the headlights (D).