Extrude problem and fine outline of a surface

Hey guys,

I have a problem to extrude a surface. I projected a cone to a plane and try to extrude the projected surface. As you can see in the image, only part of it get extruded. When I use a vertical plane for projection, the result surface (a triangle) totally can not be extruded. Could any one help me on this?

Is this because the triangle is formed by two line not closed curve? Then how to find outline of a surface? can not find sillouette in rhinoCommon. Please also help me this.

Thank you!!

Attachments:

extrude_problem.3dm, 42 KB
extrude_problem.ghx, 99 KB

Replies to This Discussion

Permalink Reply by Igor Mitrić Lavovski on October 24, 2011 at 5:22pm

Hi,

Here is tryout with Brep-Plane intersection.. It works better!

why do you want to project a cone on to plane?

Igor

Attachments:

extrude_problemRevisited.gh, 6 KB

Permalink Reply by Xiaoming Yang on October 24, 2011 at 10:14pm

Hi Igor,

Thank you for the reply. I was trying to study shadow from from a Brep (a) to another Brep (b). There are two steps, 1) project Brep a to a plane perpendicular to light 2) extrude the surface get in step 1 and intersect with Brep b.

So to complete step 1, It has to use projection. I am afraid Intersection does not work in this case. I am still struggling to understand why the extrude does not work.

Permalink Reply by Yoann Mescam (Systemiq) on October 25, 2011 at 4:20pm

I dont quite understand why the extrude doesnt work properly, but you can use Mesh Shadow to get similar result to what you expected (improve meshing quality for more exact results).

Permalink Reply by Xiaoming Yang on October 28, 2011 at 2:34am

Thank you for the reply. Actually I was trying to avoid using mesh and have smooth boundary. But I think I have to use the mash shadow for now as the extrude does not work properly in this case.

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