Today’s tutorial is the first one in a series of articles dedicated to 2d game art creation techniques. In this article, I’ll be talking about the techniques I use to preserve my game assets’ alpha channels at all times!
As game artists, we need to be very careful with our assets’ silhouette. When we paint digitally, the edges of an object may blend a bit with the background. Their opacity may vary in places… This is just fine for concept art or illustration, where the final result is a still image. In games, however, the background will scroll or change under our assets. If we mess up any of our assets’ transparency, it will be visible while playing.
Thus, most of the time, we want our assets to be drawn within a closed shape, with a sharp and consistent border. That’s exactly the type of edge vector software generate. In both raster and vector software, there is one extremely useful and flexible tool that helps to preserve an object’s silhouette at all times: Clipping masks.
A clipping mask basically limits the mask of a layer to a parent layer, put below it.
Clipping mask example: Clipping 3 layers to the character’s head
There are 3 ways to clip a layer to another in Photoshop:
1. You can keep the Alt key down and put your cursor between 2 layers, in the layers panel. When your cursor changes to an arrow pointing down, just click. And boom, you have a clipping mask!
The alt click clipping mask cursor change
2. You can also select any amount of layers and press Ctrl Alt G to toggle layer clipping on or off.
3. Lastly, you can right click on a layer’s name and click on the “Create Clipping Mask” option.
Now that we know how to use clipping masks, let’s talk about the options we have to maintain our assets’ silhouette consistency. There are 3 simple ways to maintain a sharp silhouette for your assets in Photoshop. In the case of a button, you can:
1. Use a vector shape layer or a smart object and clipping masks
2. Use a group mask. A vector mask if possible
3. Lock the layer’s alpha
All 3 options work well depending on the situation. Let’s take a look at each of them.
Technique number 1: Using a base layer
One of my cutout characters, using a base layer and clipping masks
This approach is pretty straightforward. You just want to set up a base layer that will serve as your alpha mask. And you only paint on layers clipped to it. It is a good technique if you want to use a flexible vector shape that you can edit whenever you need.
You can also use clipping masks in conjunction with smart objects in Photoshop. Photoshop can’t import external vector shapes, apart from Illustrator layers. However, it can import EPS vector files as smart objects. Sometimes, I use Inkscape to draw complex vector shapes like icons. They can’t be edited anymore once they’re dropped in Photoshop, but they can always be changed later.
Technique number 2: Using a mask
Example of two masks used to create a non-destructive stylistic effect
Masks are simply secondary alpha channels applied to a layer or a group. They limit what can be seen on the layers they affect. More precisely, they change the opacity of pixels on the layer they affect based on black and white values. If you paint with black on a layer mask, you’ll make the pixels of your source layer invisible. If you paint with white, you’ll push them back to 100% opacity. The advantage of layer masks is that they give you the ability to play with transparency in a non-destructive way. You can always delete a layer mask without losing your original work!
There is no keyboard shortcut by default to add a layer mask in Photoshop. To add a mask, you simply have to click on the “Add layer mask” icon at the bottom of your layer’s panel. If you have something selected, the mask will use your selection. And well, you can add a mask to a layer group in Photoshop, which is very handy.
Adding a layer mask in Photoshop
But there is more! You can actually use a vector shape as your mask. In the latest Photoshop versions, your layer needs to have a mask already. Then, you only have to click again on the “Add a mask icon”, which has now turned into “Add a vector mask”. If you click on it, it will add a Vector mask, based on the currently selected path.
Adding a vector mask in Photoshop
Technique number 3: Locking the layer’s alpha
Locking transparent pixels in Photoshop
In Photoshop, you can lock your raster layers’ alpha by pressing the / key. This tool is great if you want to quickly paint within your shape without messing its alpha channel. You can still clip other layers to that base layer if you want.
I like this option the most whenever I feel comfortable with a given art direction. If I need to give assets a painterly feel as well, I’ll likely shade them with a traditional painter’s approach, directly brushing on the layer.
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That’s it for this tutorial! I’ll expand this series slowly with coloring tools, common layer effects, as well as some game art specific workflow techniques.
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Original Article on GDquest.com