Requested by Oran and Crysalin! Thanks for the great idea!
While metallic textures in general have their own issues, flat, metallic items pose a bunch of unique problems. However, these problems are incredibly easily overcome through a few simple steps. I guarantee that you will be left wondering why it seemed so difficult after you read this!
This tutorial is not going to be media-specific, but I am using Photoshop CC and a drawing tablet for my examples. As always, click the images to view them bigger.
Are Flat Objects Really Flat?
One of the first things you need to determine is if the object you are coloring is actually flat. A sheet of paper is flat, a floor is generally flat, but things like a sword or a metal plate bolted on to a wall are not. What do I mean by this? I am considering something to be truly flat if it doesn’t have multiple planes, or at least not ones you can show in your drawing. AKA, two-dimensional objects. Generally, a floor is just going to be a single plane, unless it ends like on a balcony or similar structure. A standard fantasy sword however, is more like a squished rectangular prism. That metal plate bolted on the wall of your space ship is just an extremely flattened cube. They’re going to cast shadows and have highlighted planes, just like how your basic 3D shapes cast shadows and have highlights. This tutorial is going to cover items that *look* flat, but are actually three-dimensional. Some of the concepts can be easily translated into 2D objects, however.
The first thing is to do your sketch and get that inked, if you plan on using color. This entire tutorial can easily be done as just a sketch! I’ll be using a relatively flat machete from a recent commission for my example. Refer to my blog on “How I Ink with Photoshop” if you need some tips for inking your object.
While you are sketching, make sure you determine the location of your light source. For metallic objects, light sources are what determines nearly every part of how you handle coloring them. Even though you won't be able to tell how the light affects your object in the sketch stage, it's always good to have the finished piece in mind early!
TIP: If you have a habit of forgetting where your light source is, I suggest drawing a circle to represent it. You can always erase this circle after you’re done!
Got your light source sorted out? Good! Now this step is going to be incredibly simple, especially because we are working with flat planes. Think back to your basics. Remember shading a cube? We’re going to do that. Taking your light source into account, color and shade your object accordingly.
*If you are using a permanent media, or one you cannot add a lighter color on top of, such as markers, WAIT. (unless you have something like a gel pens or white pencils you can also use). Finish reading this tutorial before you begin coloring.
Your object should start looking a bit more fleshed out now, though it probably doesn’t look metallic at all.
Notice how in my example, I shaded darker towards the hilt, and allowed it to stay lighter near the tip. This is because of the angle I chose to draw the machete, as well as the placement of the light source. However, if your light source is not very strong, or it's ambiguous, I have found that shading in a gradient from hilt to tip can help make a blade look more metallic.
TIP: For an even more metallic effect, try to make your brush strokes parallel to each other. Metal often has a grain to it, that while it's not necessarily visible to the naked eye, can enhance the illusion of metallic shine. Even more so, reflections on metallic objects, especially flat ones, are often parallel lines of light and dark (unless you have a mirror or something extremely reflective!)
Now we can begin to add highlights and reflections to the object. This is why I had those of you using certain media to wait. You will color in the areas where the highlights do not hit and leave the highlights white.
Once again, remember your light source!
For my machete, I added some white highlights to the blade edge, not only because that is closest to the light source, but also because the sharpened edge is a slightly different plane than the rest of the blade and will therefore be affected by the light the same way as a cube face. I faded the highlight as the machete blade curves toward the tip because the light source is no longer hitting it the same way as the rest of the edge. I also added a thinner bright highlight to the very edge of the curve near the tip to create the illusion that the blade is extremely sharp.
TIP: If you are using markers, I like to use a white colored pencil for these highlights. If you are using a digital program, I suggest using a lower opacity for these.
In this stage we are going to add some light reflections to the object's shaded plane to even further push the metallic illusion. Remember, I shaded my machete the same way you would a cube, with the blade plane being lighter and the shaded, flat side being a different plane. You can chose to add as many reflections as you want, as your drawing dictates, but for my machete, I am only adding a couple.
Imagine if your light source has beams coming out of it like a cartoon sun. The highlights we are adding this time will be mostly parallel to those beams. In the case of my machete, they run perpendicular to the highlight on the blade edge that I added in the last step. While this might not always be the case in every drawing, it will generally work this way.
Using a very light hand, or a low opacity, add parallel lines on a shaded plane. It's generally best to add reflections like this to a plane that touches the highlighted plane, rather than the darkest plane.
TIP: Try making your reflection lines in pairs or trios of various thicknesses. I personally like to use pairs, with one line much thicker than the other one.
And now, the final touches! While we could leave the object just the way it is now, adding some bright highlights will EVEN FURTHER push the illusion of it being metallic. You can add these bright highlights anywhere that the light would create a brilliant shine, though I suggest you use them sparingly because they should POP! Think of these highlights of being that spot on a metal object where a flashlight would make a glare.
For these, you will want to make sure that your lines are thin. I would suggest treating them very similar to how you deal with inked linework, complete with tapered ends.
TIP: If you are using markers, consider using a white gel pen or white acrylic paint on a fine brush for these lines. Digital artists will want to make sure their opacity is set to 100%.
I chose to add my bright highlights to the break between the blade edge and the flat planes to better create the illusion that the blade is sharp. I also added one to reflection highlight on the flat side to suggest that the machete is both thin and sharp.
That's it! Not too difficult, right? The secret to metallic objects, especially flat ones, is creating the illusion that your object is made of metal. Unless you are doing a photo-realistic piece, all you need to do is convince your audience's mind.
If you have any questions, post in the comments on here, or hit me up on Facebook or on Twitter and I would be more than happy to answer them as best I can. And don't forget to subscribe so you don't miss the next blog!