how to extract a surface from a scanned surface

[Anonymous]

ok i scan this fender as test . i use create mesh section 4 time to create a patch . then i use fit curve to mesh section . 

now i do i create a surface from those for sketch 14 to 17 . so i can make a test molding from that surface . ?

[laughingcreek · Accepted solution]

the answer SHOULD be to use curve fit tools on those mesh sections, and then loft.  Bit the urve fit tools give a very jittery line that makes a horrible surface, and it's (i think) imposible to get the rails for the loft to be perfictly coincident with the path. (@jeff.strater - maybe you have sugestions for using the mesh section curve fit tool for this?)

So instead, I fit splines to the sections by eyball, which is sometimes good enough.  do the loft path first, then do an intersection projection for the rails to ensure they are coincedent with the path.  then loft it.

[jeff_strater · Accepted solution]

Nice work, @laughingcreek.  I found that using the Fit Curves to Mesh Section, with type set to Spline, produces pretty good approximation of the mesh section, so I would use that over manually fitting a spline:

Jeff

[laughingcreek]

@jeff_strater-how do you get the rails coincident with the profiles?

[jeff_strater]

@laughingcreek,

Oh, I did not go that far at all!  I was just pointing out an easier way to fit the curves.  But, the result of Fit Curves to Mesh Section are normal sketch curves, so Project Intersect should work OK, or at least the same as with the curves you manually fitted.

Jeff

[laughingcreek]

Also, how do you get clean lines from the fit tool?  here is a curve fit to part of the cross section at .5 mm tolerance and 2mm tolerance.  Neither one is really an acceptable starting curve for lofting.  The curve isn't acceptable even at a tolerance of 20mm, and at that point I can definitely get a better result manually. And there doesn't seem to be anyway of editing the fitted curve afterwards to make adjustments.  Do you have tips for improving the quality of the fit curves?

[jeff_strater]

The main (OK, only) control you have for this is the Spline Fit Tolerance setting.  The default is 0.01mm, and with that level of accuracy, you get very bad results:

however, if I set the tolerance to 10mm instead, I get better curvature:

The curve length of this curve is 6400mm, so a large tolerance is acceptable.  Even at 500mm, I cannot see very much deviation between the mesh section and the resulting curve, and the curvature is much better:

[Anonymous]

thank . fit splines is a better way . also thank for showing me  to use the intersect tool . before making the spline . for the cross section . before i could not make a loft . now i can !! thx again 

[Anonymous]

yes this is  the way i was doing it . work good on this particular mesh . because it is perfect and clean . 

but on a irregular scanned surface fit spine would be a better choice . i think .