This section will look at applying a Photoshop layer mask to a drawing for non destructive editing purposes. Through this demonstration, the advantages are seen as I solve a compositional problem involving object placement that can exist, due to perspective, in both the background and the foreground.
Learning the layer mask option is important part of editing drawn objects and shapes. Specifically, a layer mask will help artists hide or reveal the contents of a layer underneath based on the active layer. If that is the case, why not just erase those pixels, then?
The answer is that it create a flexible environment where the object can be repositioned. Rather than repaint the entire section of the object that was erased, it's better to just to reposition the layer mask to another section of the object, effectively hiding that section that is in the shape of the layer mask.
In this demonstration, I will be drawing a hand holding a weapon that is in the foreground, but also belongs in the background. Just follow along to see just how powerful this feature really is...as it is definitely needed to create many levels of transparency without destroying pixels!
Working with multiple layers presents a problem in that it can sometimes be hard to keep track of it all. There will be some unforeseen circumstances along the way with organization. In this example, the armor bits on one layer group. This is fine until I decided to have her hold a weapon.
However, the layer in which that the weapon is painted on, is on top of the armor layer group. I can't paint the weapon underneath the hand because then it won't show through the side skirts. To solve this issue, I need to hide the pixels of the staff that is in the shape of her hands.
To do that, I hit CTR + left click on the body layer box. If done correctly, there will be an animated dash around the object in that layer. This will create a path of the area I want to cut out in the Photoshop layer mask. With this area selected, I will now use it to create a negative space on the weapon's layer.
Note: the path selection can be expanded by hitting CTR + left click on one of layers, and then SHIFT + CTR + left click on another painting layer to include it in the path selection. Other than that, the goal here is to get just the shape of the arm.
Without a path selected, the easiest to create a Photoshop layer mask is to highlight the current layer, and then click the icon showing a grey box with a white circle on the lower section of the Photoshop layers panel. Hitting that icon will fill in the negative space and positive space of the Photoshop layer mask automatically.
The mask will show up as black and white. White represents full transparency whereas black represents no transparency. Any varying degrees of transparency will have to be drawn in using different hues of 'grays'. For example, 50% gray will represent 50% transparency.
Anyway, going back to the demonstration, one thing seems off. If I look at the miniature icon of the layer mask created, I notice that the negative space is reversed. Instead of hiding the weapon underneath the shape of the hand, it hides everything else except for grip area.
That is, instead of hiding the area of the weapon based on the selection of the hand, it's hiding everything outside of the selection! This is the default behavior as Photoshop thinks I want to retain all the information within that path. How do I resolve this issue, then?
Sometimes, when I am drawing, it can be annoying to discover that I am editing the actual object layer instead of the Photoshop layer mask. This can lead to periods of frustration as I undo the mistake. Therefore, I have to make sure that the layer mask is selected.
There will be a white graphical box highlighting the mask. The rule of thumb is to always keep an eye out for this outline before I begin editing to make sure I am not working on the actual layer! Anyway, now that I have the mask selected, hit CTR + I to invert the selection of the mask.
The result is that this will reverse the entire mask to hide everything inside the designated path of the hand like I have originally intended in one quick step. For moving the object around, there's a chain linking the mask with the drawing layer.
By clicking on the chain, I can disassociate the mask with the painting layer. This means that I can move the contents of the painting layer without moving the selection created by the mask. In this example, I can move or edit the weapon and it'll still look like she's holding it properly.
At this point of the lesson, we are almost done with the digital painting. However, if I take a closer look, the weapon is still not positioned properly. Specifically, the weapon is behind the entire hand instead of behind help properly between the thumb and the fingers.
To get it to look like it's being held firmly, I am going to repaint a part of the mask to reveal the bits of the weapon layer that is crossing over the thumbs. First, I select the paint brush and choose a pure black as the base color. Then, set the pressure sensitivity of the brush to 100%.
As mentioned before: black represents 100% opacity where white will represent 0% opacity. Painting with any grey or color in between will yield different levels of transparency. I can also do this with the eraser instead of the paint brush. The difference is that the colors would be reversed: white will be 100% opacity whereas black will represent 0% opacity.
Armed with this knowledge, I used black and painted in the section of the mask; cutting into the thumb so it looks like that she is firmly holding it properly. Not only can I use the paint brush and the eraser tool, I can also use the dodge tool, blur/sharpen tool, the gradient tool, and other basic illustration instruments on the layer mask.
For example, I can use the blur tool to smudge the layer mask and make my original layer have a blurry outline to it. As long as I know that difference colors will result in different levels of transparency on the mask, I can use it to reveal many different levels of the painting level without editing it at all.
One more thing: if I hit CTR + left click (visually, it creates a red 'X' on the layer mask), I can hide or show the mask as a means to quickly toggle between the original layer and the effects created by hiding specific pixels. I hope this lesson on Photoshop masking techniques is educational. It truly is a great non destructive editing tool.