Making Of 'Petrol Head'
Hi, boys and girls! In this article I'd like to talk about the process of creating my image Petrol Head. Here are a few words about the birth of this idea.
I was browsing the internet and found a few images of an old car carburetor. It looked really cool, with all its complex mechanisms and technological form. And I was wondering what kind of headache the idea of creating a carburetor in 3D would cause the modeler (Fig.01).
The task was pretty challenging, but making a lonely carburetor and saying something like "Look guys, I can model car carburetors" was not an option. I needed to do something more creative, and more exciting.Â So after gazing at the image for a few minutes, I decided that the carburetor looked like an eye that could be opened and closed and that the form was kind of similar (Fig.02).
After that was just... boom, here we are, that's my idea: a robot created from the parts of a car engine. I studied more images of old fashioned car engines with carburetors and all that stuff, and found many interesting parts and forms for my robot. And the more I was thinking about the character the more ideas I had (Fig.03).
His name was kind of obvious too. The thinking process was: something like an engine, needs petrol, robot created from the engine, drinks petrol ... So the name "Petrol Head" and the final composition (with the robot drinking fuel like some kind of juice) were easy to come up with.
I decided to use the following parts for the robot: an air filter like a cap carburetor for the head and eyes; an exhaust system for the ribcage and some small parts for additional details (Fig.04).
Modeling In Maya
I modeled these parts in Maya and started to think about how they could fit together (Fig.05 & Fig.06).
I also added some metal parts to the design in order to make them in different color and to make his face more expressive (Fig.07).
Some additional details were modeled using the same parts as a base and applying mirror cuts to them. After playing with the cut plane I ended up with some interesting details (Fig.08).
So the final mesh looked like this (Fig.09).
It had some holes and didn't have some parts that were not visible to camera, but as long as the model would be used only for a still render from a fixed angle then it was okay!
Now it was time to export the geometry into ZBrush. Before that I separated the mesh into different groups of details in order to make the geometry a little bit lighter after the subdivision. The idea was pretty simple: parts that were small or didn't need high SubD levels needed to be a single subtool and it's a good idea to separate your model into groups by materials also.
ZBrush Rendering Tips
The idea of rendering in ZBrush is to separate the process into passes. The number of passes depends on what you are trying to achieve and the complexity of your materials. I usually do something like ambient occlusion, specular, diffuse and reflection.
All materials for this image were default or downloaded from Pixologic's matcap library: http://www.pixologic.com/zbrush/downloadcenter/library/
In ZBrush 3.5 we have a very nice feature called "Mask ambient occlusion", which means you can get a clean AO pass in no time, but it only works perfectly if you have pretty high subD levels in your model. When your model or some of the subtools are low on polygons you can use this fake AO technique. It's not as cool as a true AO, but it can also help you to add some info about light and shadows to your diffuse renderings. Just apply any matcap to your model and then lower it's opacity to 0 in the material modifiers. After that, adjust your real-time preview shadows in the rendering palette (Fig.10).
If you have a reflective material you can use new chrome materials in 3.5, or if you need some custom reflections you can use the "reflected map material" option for your reflection pass. Any texture can be loaded into this mat and you'll get your reflections (Fig.11).
By combining different passes with different ZBrush materials you can get any effect you like. Just remember that you should be a close friend of Photoshop also. To export the passes into Photoshop I use the ZApplink plugin. When using ZApplink you'll get some extra "bonuses" in Photoshop, like all the masks ZDepth channel and the rendering itself will be separated into three different layers (ZBrush shading layer, polypainting layer and Z fill shading layer).
If you need to apply different materials to one model, the best idea is probably just to polypaint the parts that you need to separate with different colors. I think this approach is much more flexible then painting the different material son the model. If you do color painting you'll get an easy way to select these parts in Photoshop and also get any kind of material you like using passes (Fig.12).
ZDepth is great for composing. You can use this channel to get "cheap" DOF or a kind of "Fog effect" in Photoshop. To get a DOF effect I used the standard Photoshop filter "lens blur" and just loaded my depth information in there and selected my focal point... it's a really fast and easy way.
I also like to overlay different textures over the surfaces to add some dirt or rust and paint different highlights to add some rim light effects. These effects can be seen in Fig.13 & Fig.14.
My final image looks like this (Fig.15).
If you have any questions feel free to contact me via email.