Remove doubled lines

[guache]

Sometimes, after some complex modeling, I get invisible, unnecessarily doubled lines: that is, line segments that occupy the same space as some other line (pic 1). If I sort prims by X and raise each one a bit in Y based on its ID (pic 2), I can see them. Is there an easy way to get rid of such doubled lines (pic 3)? I don't care if the result is a single primitive with many points, or several 2-point line segments. The "Fuse" SOP will merge points, but it won't get rid of doubled lines.

Note: in the pic, the colors / width are just for illustration purposes. In Houdini, it's all one wireframe, you can't see the doublings. Also, the pic is just a simple example: in this case, I could remove all prims, keep the points, fuse them, then rebuild a single primitive. In real cases, the lines may be part of a grid, connect to other lines in specific ways etc, so rebuilding prims from just points would be very hard.

Edited October 21, 2020 by guache

[Librarian]

Maybe this Helps ..you have endless ways to do this depending of Your File and Case that we don't see Here
@guache

 

9 hours ago, guache said:

I don't care if the result is a single primitive with many points

//Prim
int prim_points[] = primpoints( geoself(), @primnum );
vector pos_accum = 0;

for ( int i = 0; i < len(prim_points); i++ )
{
    pos_accum += attrib( 0, "point", "P", prim_points[i] );
}

pos_accum /= len(prim_points);

int xyz_prim;
vector xyz_uv;

float xyz_dist = xyzdist( 0, pos_accum, xyz_prim, xyz_uv);

if ( xyz_prim > @primnum && xyz_dist < 0.001 )
    removeprim(geoself(), @primnum, 1);
else if ( xyz_prim < @primnum && xyz_dist < 0.001 )
    removeprim(geoself(), xyz_prim, 1);

Primi.hiplc

Prim2.hiplc

Edited October 21, 2020 by Librarian

[guache]

14 hours ago, Librarian said:

Prim2.hiplc

Thanks for looking into this. It doesn't quite work with my test case with overlapping T-junctions, meeting at odd angles etc. In the end, I created a network of ~30 or so SOPs (!)  that works for me. I exported it with opscript / old school (to avoid issues with many dependencies in my setup).

duplicate_removal.cmd

[Aizatulin]

Hi,

here is another approach (if you have not straight lines). I'm not sure if this works in every situation.

• rebuild all primitives to polylines (for xyzdist())
• for every primitive (the first one, which you are looping over) get all other primitives as list, where the first point is close enough (create a list of these primitives)
• for these candidates check the distance for all points of the primitive itself (all distances should be small)
• take the uv_i.x value of the first point and last point (of the first primitive) from the ith candidate (from xyzdist())
• check all points of each primitive i, if they are close enough to the first primitive (and between uv_i.x(0) and uv_i.x(n-1))

This method will not work for overlapping primitives (if the primitive is part pf two or more other primitives).

Here is a example file

remove_redundant_prims.hipnc

 

or brutal way:

• resample/subdivide your primitive
• measure distance to rest geometry
• if distance is small for every point -> delete

advantage (it is working for closed and open prims, also working for overlapping parts)

disadvantage (depends on subdivisions -> bad performance, not elegant)

 

remove_redundant_primsA.hipnc

Edited October 22, 2020 by Aizatulin