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This tutorial was featured in July issue
of CGInsider
mazagine.
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Definition
Compound path consists of two or more paths
that interact with each other. Compound paths are used when you
need to show a part of underlying object through a hole in another
object. Imagine a flat donut on a plate. Outer edge of the donut is
defined by one path, and the donut hole by another path. A transparent
hole occurs in the area where paths cross. Through this hole you
can see the plate underneath.
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No matter how many components make
up a compound path they all act as one unit. If you try to select
separate paths that make up the compound with Selection tool the whole
compound path will be selected. However, you can select and move component
paths with Group Selection tool (you have to click directly on path
not on fill) and edit paths with Direct Selection tool. |
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You cannot view individual components
of compound paths in the Layers palette, or give the components their
own appearance attributes (such as fill or style). All components
in the compound path take on the appearance attributes of the bottommost
object in the stacking order. Take a look at the example. Three
original paths with their own attributes after combining into compound
path became one object with uniform appearance. Attributes were inherited
from the path at the very bottom of the group.
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Making and releasing compound paths
To create a compound path:
1. Select the paths you want to include
in the compound path.
2. Choose Object > Compound Path >
Make.
To break compound path into original paths:
1. Select the compound path you want
to break.
2. Choose Object > Compound Path >
Release. Individual paths will retain appearance attributes of the
compound path. They won’t recover their original attributes
that they had before inclusion into compound path.
You can combine two or more already made compound paths into another
compound path. Or you can make compound path out of two or more groups
of paths or objects within the same group. If error dialog pops up
warning that you can’t make a compound path make sure that the
paths you want to include in the compound path don’t belong
to different groups or compound paths.
To check if your path is a compound path
select it and go to Object > Compound Path >. If Release option
is available your path is a compound path. Release it and proceed
with making a new compound.
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Adjusting the appearance of compound paths
There are two rules that may be applied to adjust the appearance of
a compound path: non-zero winding fill rule and even-odd rule. They
both use mathematical equations to determine which areas will be filled
and which will become transparent. You have to choose what rule to
apply to your path; you can’t use both of them at the same time.
The non-zero winding fill rule: in a compound path an
individual path will create a hole in another path only if it goes
in the opposite direction. When you first create a compound path non-zero
winding fill rule applied to it by default.
The even-odd rule: every other region within an even-odd
compound path is a hole, regardless of path direction.
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To apply a non-zero
winding or even-odd rule to a compound path:
1. Select the compound path with Selection
tool.
2. Choose Window > Attributes.
3. Click the Use Non-Zero Winding Fill
Rule button or the Use Even-Odd Fill Rule button.
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Path directions
Each path in Illustrator has a direction. For paths that you
draw with the Pen or Brush tool, the direction of the path is the
direction in which you draw the path. When you make shapes with Oval,
Rectangle or other shape creation tool, the initial direction of the
path is always counterclockwise.
Path directions are used to determine filled and empty areas of compound
paths. When paths are changed into compound paths, their direction
may change. In a compound path an individual path will create a hole
in another path only if it goes in the opposite direction. If both
paths go in the same direction no holes are made, the result is filled
area.
To change path direction:
1. Use Group Selection tool to select
just the path which direction you want to change.
2. Choose Window > Attributes.
3. In the Attributes palette box, click
the direction button that is not pressed.
If you select a whole compound path and click on either button all
paths will go in the same direction and no holes will be produced.
So make sure you select only the path you need.
If you want more flexibility in the compound path creation, you can
create a compound shape and then expand it. Use Pathfinder palette
for this. But this is another story, for another tutorial. :)
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