subtract from shape area - Adobe illustrator

Don't think you can do this operation with multiple shapes in one step, whether on one or multiple layers. If you do (i.e., select all shapes in a stack on one layer or across multiple layers) then all objects above will subtract from the bottom shape and result in a single compound object with the fill of the bottom shape. It's as if you first combined all the shapes above into a single object, then subtracted it from the bottom object. At least that's what happens here.

So you first copy the object that you want to use as the "cutter." Now select both the cutting shape and just one of the objects below, then subtract. Now paste in front the cutting shape, select both this copy and just one more shape from a lower layer, then subtract. Then paste in front again, and so on.

Eight pancakes would mean eight executions of the command to see a portion of the plate in the shape of the cutting object.

Maybe someone will be along to correct my understanding of this command and/or to offer a more elegant and efficient way.

I would use a knockout group (optionally at the Layer level) or Pathfinder Crop in conjunction with a compound path.

Thanks Doug,

I think I see where you're going. Just keep bringing layers to the front and subtracting my shape. Then put the layers back where they belong when I'm done. I'll try this tonight.

Knockout Group:

- Target Layer 2
- Go to the Transparency Palette and turn on the Knockout Group option

<http://illustrator.hilfdirselbst.ch/Sonstiges/Make_Hole/Make_Hole_001.gif>

- Select path 'Cutter'
- Go to the Transparency Palette and set Cutter's opacity to zero percent

<http://illustrator.hilfdirselbst.ch/Sonstiges/Make_Hole/Make_Hole_002.gif>

Pathfinder Crop:

- Create a compound path on top of the four circles

<http://illustrator.hilfdirselbst.ch/Sonstiges/Make_Hole/Crop_001.gif>

- Target Layer 2
- Go to Effect > Pathfinder > Crop
- If desired, go to Object > Expand Appearance

<http://illustrator.hilfdirselbst.ch/Sonstiges/Make_Hole/Crop_002.gif>

The same can be done in conjunction with objects on sublayers within layers.

Try Kurt's techniques too. He really knows his stuff. (Kurt, the Knockout method uses transparency, right? So if scalability's an issue he must be mindful?)

If you like my way, Matthew, I want to stress that it's not necessary to move the layers. If your cutter object's on a top layer and the object you want to cut through is three layers below, you'd merely select the cutter on its layer and the target object on its layer below and Subtract. The subraction will occur in this situation.

BUT the RESULTING OBJECT will be moved to the layer that held the cutter, not the cut object. So you may want to return the OBJECT to its original layer (in my example, three layers below).

Oh, I like diagrams.

Thanks very much guys.

the Knockout method uses transparency, right? So if scalability's an issue
he must be mindful?




Yes, transparency is used. As for the scalability aspect, I'm not sure what you mean exactly (I took a look into my old dictionary, but that didn't help much in this case).

Are you referring to performance issues?

No. I meant there would be limits on resizing... the risk of pixelization. But I think I'm wrong on this. I don't think the knockout technique rasterizes anything while still inside AI. Is this right?

Yes, unless you perform the Flatten Transparency command setting its options to convert the selection to a raster image.