[SOLVED] Polylines from near points

[josfella]

Hi,

I'm trying to create polylines between two groups of points, but not use the same 'destination' point twice.

 

The points are divided into two groups (upper and lower) and I'm using a point wrangle (with Group set to 'upper') to create the polylines:

int nrpt = nearpoint(0, 'lower', @P);
addprim(0, 'polyline', @ptnum, nrpt);
setpointgroup(0, 'lower', nrpt, 0);

By removing the destination point (nrpt) from the 'lower' point group I was hoping that nearpoint() wouldn't return that point again. It creates the polylines and removes the destination point from the point group, but it still uses that point again in the next iteration.

I thought this might be because the wrangle is multi-threaded and so the call to setpointgroup() is too late (the other threads have already done their thing) so I tried using a Detail wrangle instead:

int npts = npoints(0);

for(int i = 0; i < npts; i++) {
    if (inpointgroup(0, 'upper', i))
    {
        int nrpt = nearpoint(0, 'lower', point(0, 'P', i));
        addprim(0, 'polyline', i, nrpt);
        setpointgroup(0, 'lower', nrpt, 0);
    }
}

Unfortunately I get the same result 

Anyone got any ideas?

test .hip attached...

polyline_connect.hipnc

[Librarian]

Just play with 1 inp and 2 inp on Wrangle ( code found here on Odforce).

int drawLine(vector f; vector t){
    int base=addpoint(0,f);
    int to=addpoint(0,t);
    int line=addprim(0,"polyline",base,to);
    return line;
}
//-----------------------------

int read=0;
if(npoints(1)>0){
    read=1;
}

int maxLines=chi("maxLineCount");
float minLen=chf("minLineLength");

int pts[]=pcfind(read,"P",v@P,chf("maxLineLength"),chi("maxFindCount"));
int randomConnect=chi("randomConnect");
int keepPointCount=min(1, max(0,chi("keepPointCount")));
int runner=0;
vector curPos;
int pt;
if(randomConnect == 0){
    for(int x=0; x<len(pts);++x){
        pt=pts[x];
        
        if(runner > maxLines){ break; }
        
        curPos=attrib(read,"point", "P", pt);
        if(length(curPos-v@P)>minLen && (@ptnum<pt || read)){
            if(keepPointCount){
                int to=pt;
                if(read){
                    to=addpoint(0,curPos);
                }
                addprim(0,"polyline",@ptnum,to);
            }else{
                drawLine(v@P,curPos);
            }
            runner++;
        }
    }
}else{
    int l=len(pts);
    float fl=float(l);
    int rander=pts[int(random(@ptnum*fl+randomConnect)*fl*fl) % l];
    curPos=attrib(read,"point", "P", rander);
    if(keepPointCount){
        int to=rander;
        if(read){
            to=addpoint(0,curPos);
        }
        addprim(0,"polyline",@ptnum,to);
    }else{
        drawLine(v@P,curPos);
    }
}

 

[josfella]

Thanks @Librarian, but this seems to give me the same results 

For each point in the upper group, I want to draw a line to the nearest point in the lower group that doesn't already have a line connecting it.

I'm probably missing something, but I can't see an 'already connected' check in the code you posted?

[josfella]

Fixed it! 

In a Detail wrangle:

int npts = npoints(0);
int connected[];
//for each point
for(int i = 0; i < npts; i++) {
    if (inpointgroup(0, 'upper', i))
    {
        //find all nearest lower pts
        int nrpts[] = nearpoints(0, 'lower', point(0, 'P', i), 1000, 1000);

        //loop through lower points
        for(int j = 0; j < len(nrpts); j++) {
            //if not already connected
            if(connected[nrpts[j]] != 1){
                addprim(0, 'polyline', i, nrpts[j]);
                connected[nrpts[j]]=1;
                break;
            }
        }
    }
}

By creating a new array to store the 'connectedness' of each point I could remove the setpointgroup() logic.

Makes sense now I think about it - the wrangle was pulling in the nearpoints (and their group data) from upstream each iteration!