You can mask something in Illustrator primarily by creating a Clipping Mask, where a top object acts as a window to reveal only the parts of the objects below it that fall within its boundaries.
Understanding Clipping Masks in Illustrator
A Clipping Mask uses the shape of one object to hide or reveal portions of another object or group of objects. It's like placing an object (the mask) on top of others and then cutting away everything from the underlying objects that isn't directly underneath the mask.
The key principle is that the object you want to use as the mask determines the visible area.
Steps to Create a Clipping Mask
Creating a clipping mask in Illustrator is a straightforward process involving just a few steps:
- Arrange Your Objects: Place the object you intend to use as the mask on top of the object(s) you want to mask. This is a critical step, as highlighted in the reference:
- "The object you want to use as a mask must be placed in front of the other element."
- For example, if you want a blue circle to mask an orange star, the blue circle must be in front of the orange star in the stacking order (layers).
- Select Both Objects: Use the Selection tool (V) to select both the object you want to use as the mask (the one on top) and the object(s) you want to mask (the one(s) below).
- Make the Clipping Mask: With both objects selected, you can create the mask using one of these methods:
- Right-Click Method: As mentioned in the reference, you can "right click, and choose 'Make Clipping Mask'".
- Object Menu: Go to Object > Clipping Mask > Make.
- Keyboard Shortcut: Press Ctrl + 7 (Windows) or Cmd + 7 (macOS).
Once the mask is made, the area of the lower object(s) that falls outside the boundary of the top masking object will become invisible. The top object itself becomes the mask and loses its original fill and stroke properties, effectively becoming just the transparent boundary.
Roles in a Clipping Mask
It's important to distinguish between the two components:
| Role | Description | Position | Example from Reference |
|---|---|---|---|
| Masking Object | Defines the visible area; must be a single path. | Must be on top | Blue Circle |
| Masked Objects | The artwork whose visible parts are determined by the mask. | Below the mask | Orange Star |
Editing a Clipping Mask
After creating a clipping mask, you can still edit the objects:
- Edit Mask or Contents Separately: Use the Group Selection tool (white arrow with a plus sign) or double-click the masked group to enter Isolation Mode. This allows you to move or edit the masking path or the masked contents independently.
- Release the Mask: To remove the masking effect and return to the original objects, select the masked group and go to Object > Clipping Mask > Release (or right-click and choose "Release Clipping Mask").
Using clipping masks is a fundamental technique in Illustrator for controlling visibility and creating complex shapes and compositions.
