crossing lines and vertex ?

RJ2005 · February 16, 2006, 11:28am

If you have two lines crossing each other in the same plane

is there a way to create a vertex a the point of intersection?

Tanks & Salutations

Hazza · February 16, 2006, 11:41am

Select both edges, zoom right in to intersection point, press k use knife exact slice across intersection point, if neccesary adjust the verts to intersection point , then remove doubles, there isnt a create intersection point like in cad program as far as i know.

toloban · February 16, 2006, 1:35pm

Select two edges, go in object mode and run this:

import Blender
mesh = Blender.Object.GetSelected()[0].getData()
edges = [e for e in mesh.edges if (e.v1.sel & e.v2.sel)]
intersection = Blender.Mathutils.LineIntersect(edges[0].v1.co,edges[0].v2.co,edges[1].v1.co,edges[1].v2.co)
mesh.verts.append(Blender.NMesh.Vert(intersection[0][0],intersection[0][1],intersection[0][2]))
mesh.update()

NurbNerd · February 10, 2008, 5:14pm

Adding a vertex at the intersection of two edges. This script works great. Is there a better way directly inside Blender now?

OBI_Ron · February 10, 2008, 6:08pm

Check out the GeomTool:

http://blenderartists.org/forum/showthread.php?t=81876&highlight=geom

zyzstar · August 8, 2010, 6:19am

This worked for me in Blender 2.53 Beta:


import bpy
import geometry

sel_obj = bpy.context.selected_objects[0]
sel_obj_mesh = sel_obj.data
sel_edges = [e for e in sel_obj_mesh.edges if (e.select == 1)]

edge1_v1 = sel_obj_mesh.verts[sel_edges[0].verts[0]].co
edge1_v2 = sel_obj_mesh.verts[sel_edges[0].verts[1]].co

edge2_v1 = sel_obj_mesh.verts[sel_edges[1].verts[0]].co
edge2_v2 = sel_obj_mesh.verts[sel_edges[1].verts[1]].co

intersection = geometry.LineIntersect (edge1_v1, edge1_v2, edge2_v1, edge2_v2)

bpy.ops.object.mode_set (mode = 'OBJECT')

sel_obj_mesh.add_geometry (1, 0, 0)
sel_obj_mesh.verts[len (sel_obj_mesh.verts) - 1].co = intersection[0]
sel_obj_mesh.update()

bpy.ops.object.mode_set (mode = 'EDIT')

RickyBlender · August 8, 2010, 7:04am

this seems to be for 2.5

why don’t you open up a thread in python forum and show this might be usefull snippet for 2,5

happy 2.5

barrasn · August 8, 2010, 10:13am

You should be able to do it without scripts… just select one of the edges, subdivide it, do the same for the other edge, then select both new vertices and press alt-m to merge. hope this helps!

amoose136 · August 8, 2010, 9:57pm

You should be able to do it without scripts… just select one of the edges, subdivide it, do the same for the other edge, then select both new vertices and press alt-m to merge. hope this helps!

That will only work if the lines intersect at both of their middles.

MCollett · August 8, 2010, 11:35pm

In 2.49 you can use the knife: snap cut marks to the ends of one line, and it will create a new vertex at the appropriate point on the other. Unfortunately, that functionality (snapping the knife) is missing from 2.53.

Best wishes,
Matthew

RickyBlender · August 9, 2010, 11:39am

@zysstar

i tested your little sript in 2.5

and it’s giving an error on line 6

do you know how to correct this?

i need to get access to vertex coordinates so this may do it but not certain

Thanks

zyzstar · August 10, 2010, 2:29am

@RickyBlender

Select two edges (Edge select mode) in “Edit Mode” (lines must intersect)
Run the script
There should be a new vertex added at intersection (switch to “Vertex select mode” to see that)

Here’s an updated version which also prints all vertex coordinates:


import bpy
import geometry

bpy.ops.object.mode_set (mode = 'OBJECT')

print ("------------------------")

sel_obj = bpy.context.selected_objects[0]
sel_obj_mesh = sel_obj.data
sel_edges = [e for e in sel_obj_mesh.edges if (e.select == 1)]

print ("Number of selected edges: ", len(sel_edges))

edge1_v1 = sel_obj_mesh.verts[sel_edges[0].verts[0]].co
edge1_v2 = sel_obj_mesh.verts[sel_edges[0].verts[1]].co

edge2_v1 = sel_obj_mesh.verts[sel_edges[1].verts[0]].co
edge2_v2 = sel_obj_mesh.verts[sel_edges[1].verts[1]].co

print (edge1_v1)
print (edge1_v2)
print (edge2_v1)
print (edge2_v2)

intersection = geometry.LineIntersect (edge1_v1, edge1_v2, edge2_v1, edge2_v2)

print ("Intersection vertex:
", intersection[0])

sel_obj_mesh.add_geometry (1, 0, 0)
sel_obj_mesh.verts[len (sel_obj_mesh.verts) - 1].co = intersection[0]
sel_obj_mesh.update()

bpy.ops.object.mode_set (mode = 'EDIT')

RickyBlender · August 10, 2010, 5:22am

i was testing in last week version 175
then i got yesterday the 31197 and tested it and now it works ok

the only thing is that the new point is not part of the 2lines it’s and independant object !

but i guess there is a way to create a nw line by re doing a new line with this point

thanks

RickyBlender · August 10, 2010, 7:04am

are you going to open a thread on python or i do it to share this finding
for line intersect ?

might be usefull for someone else in 2.5

happy 2.5

zyzstar · October 25, 2010, 11:24am

Updated script for Blender 2.54 Beta


import bpy
import geometry

bpy.ops.object.mode_set (mode = 'OBJECT')

print ("------------------------")

sel_obj = bpy.context.selected_objects[0]
sel_obj_mesh = sel_obj.data
sel_edges = [e for e in sel_obj_mesh.edges if (e.select == 1)]

print ("Number of selected edges: ", len(sel_edges))

edge1_v1 = sel_obj_mesh.vertices[sel_edges[0].vertices[0]].co
edge1_v2 = sel_obj_mesh.vertices[sel_edges[0].vertices[1]].co

edge2_v1 = sel_obj_mesh.vertices[sel_edges[1].vertices[0]].co
edge2_v2 = sel_obj_mesh.vertices[sel_edges[1].vertices[1]].co

print (edge1_v1)
print (edge1_v2)
print (edge2_v1)
print (edge2_v2)

intersection = geometry.LineIntersect (edge1_v1, edge1_v2, edge2_v1, edge2_v2)

print ("Intersection vertex:
", intersection[0])

sel_obj_mesh.vertices.add (1)
sel_obj_mesh.vertices[-1].co = intersection[0]
sel_obj_mesh.update()

bpy.ops.object.mode_set (mode = 'EDIT')

zyzstar · October 25, 2010, 11:26am

Please do whatever you feel is right.

hypnos78 · November 14, 2010, 8:57am

the 2.55 version doesnt seem to have the geometry module anymore. this one is based on the above code and code taken from addons/space_view3d_spacebar_menu.py:


import bpy
from bpy import *
from mathutils import Vector

def LineLineIntersect (p1, p2, p3, p4):
    # based on Paul Bourke's Shortest Line Between 2 lines
    
    min = 0.0000001
    
    v1 = Vector((p1.x - p3.x, p1.y - p3.y, p1.z - p3.z))
    v2 = Vector((p4.x - p3.x, p4.y - p3.y, p4.z - p3.z))
    
    if abs(v2.x) &lt; min and abs(v2.y) &lt; min and abs(v2.z)  &lt; min:
        return None
        
    v3 = Vector((p2.x - p1.x, p2.y - p1.y, p2.z - p1.z))
    
    if abs(v3.x) &lt; min and abs(v3.y) &lt; min and abs(v3.z) &lt; min:
        return None

    d1 = v1.dot(v2)
    d2 = v2.dot(v3)
    d3 = v1.dot(v3)
    d4 = v2.dot(v2)
    d5 = v3.dot(v3)

    d = d5 * d4 - d2 * d2
    
    if abs(d) &lt; min:
        return None
        
    n = d1 * d2 - d3 * d4

    mua = n / d
    mub = (d1 + d2 * (mua)) / d4

    return [Vector((p1.x + mua * v3.x, p1.y + mua * v3.y, p1.z + mua * v3.z)), 
        Vector((p3.x + mub * v2.x, p3.y + mub * v2.y, p3.z + mub * v2.z))]


print ("------------------------")

sel_obj = bpy.context.selected_objects[0]
sel_obj_mesh = sel_obj.data
sel_edges = [e for e in sel_obj_mesh.edges if (e.select == 1)]

print ("Number of selected edges: ", len(sel_edges))

edge1_v1 = sel_obj_mesh.vertices[sel_edges[0].vertices[0]].co
edge1_v2 = sel_obj_mesh.vertices[sel_edges[0].vertices[1]].co

edge2_v1 = sel_obj_mesh.vertices[sel_edges[1].vertices[0]].co
edge2_v2 = sel_obj_mesh.vertices[sel_edges[1].vertices[1]].co

print (edge1_v1)
print (edge1_v2)
print (edge2_v1)
print (edge2_v2)

intersection = LineLineIntersect (edge1_v1, edge1_v2, edge2_v1, edge2_v2)

print ("Intersection vertex:
", intersection[0])

bpy.ops.object.mode_set (mode = 'OBJECT')

#sel_obj_mesh.add_geometry (1, 0, 0)
sel_obj_mesh.vertices.add(1)
sel_obj_mesh.vertices[-1].co = intersection[0]
sel_obj_mesh.update()

bpy.ops.object.mode_set (mode = 'EDIT')

Seminumerical · November 15, 2010, 12:08pm

Try
import mathutils.geometry

:EDIT:
or better still…

from mathutils import geometry