SELECT isohypse or horizontal terrain contour - vertices sharing same Z

Support Basics & Interface
1

Hi, I have imported a terrain modeled from “isohypse” or horizontal terrain contour, and looks fine when smoothed.
BUT I want to see these lines also when the terrain is smoothed.
See screenshot (“isoipse_other” from an other software).
So I need the select these edge all (the one sharing same Z) and only them.
So I can later give them the corrisponding property in render.
Is there a Short way ?
thank you

isoipse_blender.pdf (413 KB)

isoipse_other.pdf (1.26 MB)

Attachments

isoipse.blend.zip (2.19 MB)

2

we did a script last year to do that
but have to find where I put this thing !

but that would do it all over not over a simple loop!

happy bl

3

It wolud be great!
I hope you find it.

I did try a boolean operation with a plane (array along the Z axis) , so to say it “draws” the lines again, but the shape is too complex and does not works.
I remeber as well you could do it in render through the “modulo” math node, but I have to find again how it works.

4

more or less lik this, though is not (yet) perfectly horizontal, don’t know why. see screenshot.
isoipse.pdf (1.69 MB)

BUT still I do need the other method, selectiong corresponding edges, to use it not only in rendering, for instance in opengl preview and other uses.

5

with nodes it affects only the material and texture

cannot find it right now
but I redid some script for it using Bmesh
now problem is that if you use = values I mean this is so precise you might never find one !

so need to more or less use a range -very small one but at least will find some values close to some Z value

happy bl

6

try something like this in text editor

at beginning of program set the Z value and delta value

don’t foget this is reading the local vets value so it ahs some plus or minus value compare to origin


 
import bpy
import bmesh



 

zheight = 0.5
delta = 0.1
print ('zheight =',zheight )
print ()
 
def main(context):
 
 
 global zheight , delta
 
 for ob in context.selected_objects:
 
  edbm = False
  if ob.mode == 'EDIT':
   edbm = True
   
  if edbm:
   bm = bmesh.from_edit_mesh(ob.data)
  else:
   bm = bmesh.new()
   bm.from_mesh(ob.data)
   
  for v in bm.verts:
  
   if v.select or not edbm:
    # Translate all verts if object is in object mode,
    # selected verts only if in edit mode.
    
    
    if  ( v.co[2]  >= zheight - delta ) and ( v.co[2]  <= zheight + delta ):
     v.select =True
     print ('v.co[2] =', v.co[2] , ' z - =', zheight - delta , ' z + =', zheight + delta )
#      v.co += v.normal * 0.2
    else:
     v.select = False
   
   
  if not edbm:
   bm.to_mesh(ob.data)
  ob.data.update()


 print ()
 print ('zheight =',zheight )
 print ()


class SimpleOperator(bpy.types.Operator):
 """Tooltip"""
 bl_idname = "object.simple_operator"
 bl_label = "Simple Object Operator"

 @classmethod
 def poll(cls, context):
  return context.object is not None

 def execute(self, context):
  main(context)
  return {'FINISHED'}

##########

def register():
 bpy.utils.register_class(SimpleOperator)
def unregister():
 bpy.utils.unregister_class(SimpleOperator)  
 
 
if __name__ == "__main__":
 register()
 # test call
 bpy.ops.object.simple_operator()

happy bl

Attachments

z1.PNG634×590 53.6 KB

7

Very nice, it works!
Provided that you remember to select everything, because the script does not select, but de-select.
This said, I’ve made an error:
I thought it was enough to select vertices and then, with vertices selected, you switch to edge mode and you set the properties you need.
In my case, as soon as I switch to edge mode, blender select ALL edges and vertices, not only edges connecting selected vertices.
I can’t figure out why.

I’m not very confindent in Python, so could you suggest me where the change the syntax from “select vertices” to “select edges” ?

Thank you again.

8

problem is that edge are not at same level in Z
can select only with verts at Z value !

run script in object mode
not certain why it does not work in edit mode !

and I tried to go into edges mode
problem is that you might select other edge connected to the selected verts !

happy bl

9

hi ricky,
In object mode the script works better, even as the workflow is not so straight forward:

  • go in vertices select mode
  • deselect everything
  • go in object mode
  • run the script
  • go back in edit mode
  • switch to select edges with those vertices selected
  • assign the property as needed (edge crease and freestyle)
  • repeat.

It seams we need in the script something to “reset” selection befor running the script,
and it does not work in edit mode, as the program had a hidden “memory” of selected edges.
It seems to be a common issue:

For edges, blender calculates the midpoint, and that stays on the same Z value.
So it might be worth the effort.
I’m not sure if the point is this
“for v in bm.verts:”
so I’ve searched and found this:


witch could lead to this:

import bpy, bmesh
me = bpy.context.object.data
bm = bmesh.new()
bm.from_mesh(me)
EPSILON = 1.0e-5
zheight = 2.5
for vert in bm.verts:
if ( vert.co.z >= zheight - EPSILON ) and ( vert.co.z <= zheight + EPSILON ):
vert.select = True
for edge in bm.edges:
if edge.verts[0].select and edge.verts[1].select:
edge.select = True
bm.to_mesh(me)
bm.free()

10

problem is that list of edges might
still have to find common verts to these edges !

and don’t remember you can get average height for edge !

will look at it a bit later today

happy bl

11

there is also the mesh itself
is it very high res so edges length are very short
or low res and very long edges ?

happy bl