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Roof Intersection


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In a top or top plan view, trace over the intersecting roof with the polygon tool, marking where the other roof should be trimmed. Be sure the polygon is closed.

Select the polygon and either cut or copy the polygon.

Select the roof to be trimmed.

Go to Modify>Edit Group.

Go to Edit>Paste in Place to past the polygon used as the "cookie cutter".

Without doing anything else, click on the Exit button in the upper right corner.

The pasted polygon should have cut a hole out of the roof.

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Katie, Thank you for the response, I am aware of the method you describe. To create the polygon I would have to do some fancy calculation (the intersetion I believe is an elipse) as the intersecting line does not show graphicaly in plan. I was hoping that there would be a way to treat the two roof sections; The barrel, which is an extrude and the sloping roof, which is a roof face, as soldids and subtract one from the other. The roof face does not seem to be recognized as a solid. When I ungroup the roof face it revert to the 2D polygon from which it takes its shape. Any other ideas?


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If the object is a roof rather than a roof face, simply use Edit Group - there's no need to convert to group or ungroup.

If the object is a roof face, then you'll need to adjust the original 2d object to account for the "hole".

When you look at the two roofs (if on the same layer) you should see where the two intersect and then be able to trace over it. There's an elipse tool that will let you create the elipse along the top. I would then add a rectangle to the elipse to make the entire shape - think of doing it in a series of steps.

You can then use this shape to clip the surface of the original 2D object of the roof face, or paste in Edit Group mode if the object is a roof object.

Edited by Katie
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I haven't tried this so I don't know if it works but how about trying something along the lines of...

Create a duplicate of the barrel vault

Create a plane that lies on the roof surface

Section/split the 2nd barrel vault with the plane

Use the 'extract curve' tool to get the relevant curve from the split vault

In plan view convert it to a 2D shape and then plug that into Katie's suggestion.

Like I say, I haven't tested this so it's just a suggestion,



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Thank you both for the input. Both methods worked just fine. Once I realized that one has to "render" the roof in plan to see the intersections, tracing an ellipse and cliping it from the 2d roof face polygon was a snap. I also created two extrustions that duplicated the barrel and the roof face, subtracted the solids, extracted the curve, created a polygon and cliped it from the 2d roof face polygon.

Thanks Roof Intersection.JPG

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