Rebuilding 3D curves from projections

Rebuild%203D%20crv%20from%20projections.gh Rebuild%203D%20Crv%20from%20projections.3dm

Work has begun on our measuring device!! We are trying to rebuild a single 3D curve from two projections of that curve that are on planar surfaces. The Resulting projection curves are plugged into grasshopper, then we attempt to average them back into the original curve. However, the curve that results from the average is different than the original. It might have to do with how the average is derived, but let us know if you have any suggestions.

Thx,

Group #1

Replies to This Discussion

Permalink Reply by Michael Riggin on February 14, 2014 at 9:44am

Andy, can you post the files of what you have so far?

Permalink Reply by Andrew Schiffer on February 14, 2014 at 2:35pm

here they are

Attachments:

Rebuild3DCrvfromprojections.3dm, 440 KB
Rebuild3Dcrvfromprojections.gh, 18 KB

Permalink Reply by Michael Riggin on February 16, 2014 at 12:42am

Andy, I took a look at what you are attempting to do. The issue is that you are dividing two curves the same number of times, but these curves are projections, and they are not the same length (due to foreshortening/elongation). So the division points are are falling along points on each respective curve at coordinates that will not line up across the two lists.

I investigated a couple of methods instead for quite a while, but each had a limitations and ultimately did not work. It seems much easier to draw the curve manually from one view in Rhino, and use the other view to adjust the missing dimension using control points.

Permalink Reply by Andrew Schiffer on February 16, 2014 at 1:47pm

Mike, thanks for the response. This initially seemed like it would be a fairly simple thing to do, but I guess we'll have to take a different approach. When rebuilding from the two (or three) views in Rhino, is there anyway to lock in the length of the curve so that it remains constant regardless of the control point locations? I know we are working with a finite length of tubing so I want to make sure the rhino model doesn't exceed the 20ft that we have.

Permalink Reply by Michael Riggin on February 18, 2014 at 12:16am

Andy, take a look at this definition I put together. If the curve is longer than 20', it trims off the ends and keeps the middle 20'. If it is shorter, it extends it by the same amount at both ends to equal 20' overall.

Long Curve: