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# extrude the region resulting between a bunch of intersection() lines

Member, OS Professional Posts: 216 PRO
Let's say I select four faces on a model, then use the intersection() function to create four lines at the intersection between the input faces and some arbitrary plane. Let's say that these intersecting faces are perpendicular to each other, and thus there is only one closed region defined by the boundary: a rectangle.

Question 1: How might I extrude this rectangle?

To make matters more complex, let's say that the input faces are *not* parallel. This means there are now at least two regions resulting from the (infinite) plane intersection lines we've created.

Question 2: Assuming that Question 1 above has an answer, how would I then figure out which region to extrude given non-parallel intersection() lines?

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Onshape Employees, Developers, HDM Posts: 1,185
Because solid modeling is currently more developed in FS than sheet modeling, I'd actually construct half-space extrusions (past a bounding box) from the lines and use an opBoolean to intersect the resulting solids.

An alternative if you really want a region, is to make a sketch with the four skLines (again extending out far).  Once the sketch is solved, that will create a bunch of convex regions.  For each region, you can get a point in the interior by taking the average of vertex positions.  You can then test the point against the original face planes (which you can get with evFaceTangentPlane) -- only one point will be to the negative side of all of the planes, and that one belongs to the region you want.
Ilya Baran \ VP, Architecture and FeatureScript \ Onshape Inc
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Member, OS Professional Posts: 216 PRO
Brilliant. Is there something more to half-space extrusions than making a Really Big Rectangle and extruding it Really Far?
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Onshape Employees, Developers, HDM Posts: 1,185
No, that's what I meant
Ilya Baran \ VP, Architecture and FeatureScript \ Onshape Inc
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Member, OS Professional Posts: 216 PRO
Cool! For the record, what counts as "Really Big" in Onshape? 50m? 500m? 50km?
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Onshape Employees Posts: 74
Forget everything you know about cosmology.  The universe is a cube 1 km on a side, centered on the origin.