Motorcycle Rendering Tutorial for Photoshop, creating a 'photoreal' 2D motorcycle

Hi there and welcome to my second tutorial. Perhaps weird to do so, but I would like to open with a word of advice. My mind can be quite chaotic at times, during this tutorial it certainly was. I made a number of silly mistakes and I'll show them to you in the course of the tutorial. So please read through the whole tutorial first.. you'll notice some things that I would change from the start if I were to make this image over again.
If you don't quite understand what happened in a certain step of the tutorial, just read on, there's a chance that I will explain in a later step to prevent having too much text with some images.

If you're familiar with the field of concept design, you'll probably have heard of a guy named Scott Robertson (website drawthrough.com). He has produced an excellent set of tutorial dvd's for The Gnomon Workshop, one of which shows the process of rendering a futuristic bicycle.
My tutorial uses the same techniques, though perhaps my approach will differ here and there. Anyways, Scott gave me his permission to publish this tutorial, for which I'm grateful.

Right, lets get this thing on the road.
In the Photoshop screenshot below you can see I have started out with a background and an enlarged rough sketch that I prefered to render out. Between the really messy sketchlines you'll probably see some cleaner lines that I imported from Rhino. They were traced from a Yamaha R1 motorcycle sideview. I used these to make sure my proportions wouldn't be too far off.
Put the sketch that you want to render out on a seperate layer and set the layer to Multiply and turn down the layer opacity so that it is just visible enough to be usable for tracing.

The background you see is very typical for studio photographs of cars and other vehicles. In the renders I made below you can see the effect I tried to accomplish.
Making this background is really easy, you could do the whole thing with a simple gradient, I simply used some big soft airbrushes from the default Photoshop palette. Try to avoid using the opacity of 100%, if you turn it down you can achieve much softer effects if you make a couple of passes with the brush (think of it as using a tissue with chalk powder).

I put down a simple drop shadow here, it will make a big difference in a few more steps.. Simply use a soft and small airbrush to create the shadows.
Now I will probably modify the shadow later on when the bike render is done, but for now it's good to just have an indication there of an object that is shown in this studio setup. You don't want to render a bike that seems to be hovering over the ground. A shadow gives an immediate effect of mass.

Notice the basic layer setup:

sketch guide: the initial sketch + rhino proportions drawing; layer set to multiply (so it will display over all the objects below. I set the layer to an opacity of about 40%, just enough to keep it useful for throwing down some Photoshop Paths later on.

Layer 2: still empty, but imagine in this place all the layers needed to create the actual bike rendering later on.

ground castshadow: I think this one is pretty obvious. Don't merge it with the background though, if you want to move your bike later on you don't have to create a new background and shadow if you keep things seperated.

background: the background shot that we created earlier on.

Ok, important step here, you can chose to do it later, but I prefer to lay down some guides as soon as possible.
Activate the rulers with Ctrl+R, click on the left ruler and drag till you see the guide on your image. You'll need two vertical guides, once for each wheel. Locate them to where you want to have the center of each wheel (axle position).
Now from the top ruler click/drag three guides on your image. Position one of them where your wheels will touch the ground and the other two on your wheel axles. I dropped my rear axle slightly higher than the front one, I want to have a bigger rear than front wheel.

ADVERTISE

Time to start the tedious stuff Paths!!

Lets start of with the wheels. Click the Ellipse Tool (U) and before you draw some ellipses, make sure that in the Options bar below the Taskbar this icon in pressed . This will make sure that the ellipses you're about to make will be made as paths and not shapes.
Draw an ellipse with the Shift key pressed. This will force the ellipse to become a circle.

Now your circle is probably too small or too big and not positioned where you want it. We'll solve this First you have to make sure you have snap turned on ( Shift+Ctrl+; ).
Press the Path Selection Tool , select the circle you just made and drag it onto the intersection of your guides. With some dragging left/right and up/down you'll soon enough see your new circular path snapped to the guides.
With the Path Selection Tool, we'll now scale your path so that it drops right onto the guide you made for the floor. Chose Edit > Transform Path > Scale. With the handles around your path you now can scale your path. Make sure you keep Shift pressed so that you won't stretch it back to an ellipse
Again, it might take some effort for the handles of the transform box to snap to your guide, but with some persistance it should work just fine. Press Enter to approve your scale and that's one circle done

Now we need a couple of these circles.. I created one for the outer edge of each tire as well as inner edge where the rim will start. A fifth circle was made for the shape where the rear wheel suspension will hinge.

First thing you'll probably notice here is I flipped the image horizontally. Why? Well I prefer to sketch motorcycles with their front wheel to the left. The reference photo I used showed the other side of the motorcycle, with the front wheel to the right. So my sketch had parts on one side that would be on the other side on a real motorcycle (at least, on Yamaha motorcycles in that range). I found this out around this step in the process... so I simply flipped my image horizontally (notice, if you flip your layers individually, their orientation in respect to eachother might be lost, because the layers are flipped around their own pivot points. You won't have this problem when you flip your whole image in one go.. which would be faster anyways, but it's good to know ).

Now it is time to make the rest of the paths for our rendering. Paths are vector shapes that are stored inside your drawing as invisible objects, meaning, when you save your image as a .jpg or some other format than .psd, it will not show those paths in your image.
Paths can be used for all kinds of things, but in our image we will use them to create very smooth linework and selections. You can create as many paths as you want and you can always select or deselect them and even modify them.

We will create paths for pretty much all our coloured areas. You can create a path using the Pen Tool (P). Just make sure you have this Paths button selected in your tool bar or else you will be drawing shapes instead of paths.
Draw your paths around the area that you want to colour. Maybe you are wondering 'how do I create two exactly the same bits of linework on the borders of two areas? Do I need to neatly trace the whole border of each coloured area?'. Well, don't worry because you can most likely overlap the paths in those areas, as long as we pay attention to the layer order. This means you can use the border of the one area and have the neighbouring area just overlap because it will be below it anyways.
This can be quite a puzzle, so be carefull where you think you can overlap paths and where it will be harder.

When you create the path, a single mouseclick for each new control point wil create a sharp corner.. if you click and drag you will create a smooth control point.