Forums Technical Discussion How to remove points but keep lines?

How to remove points but keep lines?

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Candace Sun
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I want to remove the selected points in Figure 1 (these points have been defined in the group) but keep the lines. I hope it looks like picture 2 after removing. I tried 'remove inline points', but it didn't work as expected.

Can anyone help?
Thank you so much!
Edited by Candace Sun - Aug. 3, 2023 01:34:31

Attachments:
2023_07_28_15_38.08.bmp (1.1 MB)
2023_07_28_15_38.21.bmp (1.1 MB)
RemovePoints.hip (153.5 KB)

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tamte
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assuming your polygons are closed or if they are open that the end points are not in your point group

you can use Blast SOP and specify your group
or Delete SOP set to Points

however Facet SOP with Remove Inline Points should work in your case as well, with same assumptions
Edited by tamte - Aug. 1, 2023 16:03:05
Tomas Slancik
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Benyee
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64669804
I want to remove the selected points in Figure 1 (these points have been defined in the group) but keep the lines. I hope it looks like picture 2 after removing. I tried 'remove inline points', but it didn't work as expected.
In this case you can try filtering points by calculating point angles with vex.
int pts[]=expandpointgroup(0,'group1');
int nb_pts2[];
string edges='',edge;

//
foreach(int pt;pts)
{
    int nb_pts[]=neighbours(0,pt);
    for(int i=0;i<len(nb_pts);i++)
    {
        int ingrp=inpointgroup(0,'group1',nb_pts[i]);
        if(!ingrp)
            {   
                pop(nb_pts,i);
            }
        else
            push(nb_pts2,nb_pts[i]);
    }
    //printf('%d\n',len(nb_pts));
    
    //
    int pt_nb0=nb_pts[0];
    int pt_nb1=nb_pts[1];
    vector pos0=point(0,'P',pt_nb0);
    vector pos1=point(0,'P',pt_nb1);
    vector cur_pos=point(0,'P',pt);
    vector dir0=normalize(pos0-cur_pos);
    vector dir1=normalize(pos1-cur_pos);
    
    float angle=degrees(acos(dot(dir0,dir1)));
    setpointattrib(0,'angle',pt,angle,'set');
    if(angle>175)
    {
        setpointgroup(0,'smooth_pts',pt,1,'set');
    }
    
}

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calculate_pointangle.hip (129.5 KB)

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Candace Sun
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Thank you very much for your replies, but I followed your approach and still haven't got the result I want. I uploaded my hip file, can you please use my file to achieve it?
Thank you for your time!
Edited by Candace Sun - Aug. 3, 2023 01:35:39

Attachments:
RemovePoints.hip (153.5 KB)

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tamte
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your outline are made of many curve segments
the best is to convert them to closed curves using PolyPath
then you can remove inline points using Facet SOP
and if you want open back up using Ends SOP

Attachments:
RemovePoints_fix.hipnc (162.5 KB)

Tomas Slancik
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Method Studios, NY
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mestela
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Ah, it's because you don't have 1 path, its lots of little segments that happen to line up next to each other.

A polypath sop will join them all into a single primitive, then you can use facet with 'remove inline points'.

Attachments:
RemovePoints_fix.hip (173.7 KB)

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mestela
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DAMNIT TOMAS BEAT ME AGAIN
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Candace Sun
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tamte
your outline are made of many curve segments
the best is to convert them to closed curves using PolyPath
then you can remove inline points using Facet SOP
and if you want open back up using Ends SOP
That's exactly what I want! Thank you Tomas, this is really helpful!
I don't know why when I added 'PolyPath' in my own file, it was displayed differently from your file, but luckily the 'Ends' solved this problem finally.
Edited by Candace Sun - Aug. 3, 2023 05:20:15

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2023_08_03_17_17.35.bmp (1.6 MB)

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Candace Sun
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Also thanks to Benyee and mestela!
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khomatech
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Didn't know Facet did that, I solved this issue recently by comparing each point's neighbouring points and deleting said points if they were both on the same axis. Only works if your lines are perfectly straight, I guess.
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cncverkstad
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vector src0 = point(0,"P",hedge_srcpoint(0,@vtxnum));
vector dst0 = point(0,"P",hedge_dstpoint(0,@vtxnum));
vector dir0 = normalize(dst0-src0);

int nexth = hedge_next(0,@vtxnum);
vector src1 = point(0,"P",hedge_srcpoint(0,nexth));
vector dst1 = point(0,"P",hedge_dstpoint(0,nexth));
vector dir1 = normalize(dst1-src1);

if(dot(dir0,dir1)>1-0.002){
    
    removevertex(0,nexth);
    int pt = vertexpoint(0,nexth);
    int l = len(pointvertices(0,pt));
    if(l<2) removepoint(0,pt);
}

sec solution
int nears[] = neighbours(0, @ptnum);
vector last_dir = point(0, "P", nears[0])-point(0, "P", @ptnum);
vector next_dir = point(0, "P", nears[1])-point(0, "P", @ptnum);
if(abs(dot(last_dir,next_dir))>0.99){
    removepoint(0,@ptnum);
}
Edited by cncverkstad - Aug. 22, 2023 05:56:32
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eaniix
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Can't you just do this?

if(@N == {1, 0, 0} || @N == {0, 0, 1} || @N == {-1, 0, 0} || @N == {0, 0, -1}){
    removepoint(0, @ptnum);
}

Should work since you want to remove all points that are either pointing -x/+x or -z/+z
Edited by eaniix - Aug. 19, 2023 08:38:46
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Jikian
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eaniix
Can't you just do this?

if(@N == {1, 0, 0} || @N == {0, 0, 1} || @N == {-1, 0, 0} || @N == {0, 0, -1}){
    removepoint(0, @ptnum);
}

Should work since you want to remove all points that are either pointing -x/+x or -z/+z

Not the wisest to perform direct == comparisons when working with possible floating point values. Fuse > Polypath > Facet (remove inline) is the "Houdini" solution that will work regardless of orientation.
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