Cut Geometry with a Solid Form

I’m trying to cut a smooth seat shape into the rocks I’ve designed in sketch up. I’ve tried using the subtract tool but the rocks unfortunately aren’t solid forms and the solid inspector add on found the rock shapes too detailed. Instead I tried to intersect faces with selection but its taking too long to delete the unnecessary lines.

Does anyone know an easy way to do this?

Rock seat.skp (5.7 MB)

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A couple of options options. Make the rock object solid so you can use Solid Tools (you may need to simplify the rock geometry too) or make a copy of the seat shape and use Intersect Faces. Then erase the unneeded geometry from the rock making sure to correct any reversed faces. The second option is often faster because you can limit the amount of geometry that needs to be looked at for intersections. The Solid Tools have to iterate through all of the faces in the objects.

Thank you for letting me know about the file.

I’ve tried using intersect faces but there are far too many lines to erase.

You’ve got an awful lot of geometry to deal with. It wouldn’t hurt to simplify the rock. Turn on Hidden Geometry temporarily so you can be surgical about the geometry you select and use Intersect Faces>With Selection. Then turn off Hidden Geometry so you can select and delete surfaces.

It would also help if you convert the rock to a component and then use the Dave Method. That will help you avoid the tiny faces issue.

retopo_rock seat.skp (5.2 MB)
rock retopologized