evaluateSpline: Parameter at index 0 is outside the knot vector

Jonathan_Hutchinson

I used a Split feature on a curve (helix) entity, and wanted to then subdivide this split version of the entity into line segments. However, I got the below error. Is this because the curve needs to in an ideal world be reparameterised between 0 and 1? Has the split operation done some funky business where it's almost treating it like a trimmed surface, and now no longer exists in the domain of the curve? I couldn't initially see anything in the FS documentation to fix this.

@evaluateSpline: Parameter at index 0 is outside the knot vector.

GregBrown

Correct, you'll often see knot vectors with domains other than [0.0 ....1.0] - particularly when trim, project etc operations have been performed. You'll likely have to do a bit of rescaling of the parameter you pass into the evaluation.

Jonathan_Hutchinson

Hey Greg, thanks for the quick response. I think we spoke in London briefly at the Design Alliance.

The hack I did was then using a path instead (FS: evPathTangentLines to evaluate point at parameters) which was a bit more clunky I suppose, but seemed to be the workaround to reset to 0-1 again. Is there an option somewhere else to reparameterise or, as you mention, rescale the parameter before subsequent operations without Paths?

Jacob_Corder

If you want to normalize the not array, i use this

export function normalizeKnotArray(knots is array)returns array
{
    var ret = knots;
    var minKnot = ret[0];      
    var ct =size(knots);
    if(minKnot !=0)
    {
        //resets knots to start at 0
        for(var j=0;j<ct;j+=1)
        {
            ret[j] = ret[j] - minKnot;
        }
    }
    var newMax = ret[ct-1];
  
    if(newMax!=1)
    {
        //normalizing the max knot to be 1 and all others scaled in between.
          var mult = (1/newMax);
        for(var j=0;j<ct;j+=1)
        {
            ret[j] = ret[j] * mult; 
        }
    }
    return ret; 
}