HI,

Is there a function that take 2 list of vertecies (liste_to_be_tested and list_already_in_a_plane) and return the list of vertecies from liste_to_be_tested that are in the same plane as the one in list_already_in_a_plane ?

Thanks

yes, it’s called cosine

dot the vector of the plane defined by ABC normal with the vector from any point in the plane (conveniently A,B or C) to the points P you are testing.

If you mean a built in function, you may want to check out geometryutils. can’t remember what’s in there

edit: Re-reading your qeustion, I think you mean something more built in.

```
>>> geometry_utils.geometry.
area_tri(
barycentric_transform(
box_pack_2d(
distance_point_to_plane(
interpolate_bezier(
intersect_line_line(
intersect_line_line_2d(
intersect_line_plane(
intersect_line_sphere(
intersect_line_sphere_2d(
intersect_plane_plane(
intersect_point_line(
intersect_point_quad_2d(
intersect_point_tri_2d(
intersect_ray_tri(
normal(
tesselate_polygon(
```

I’m thinking that “distance point to plane” will be your best bet. If that distance is 0…it’s co planar. You can easily write you own function to test a whole list of points and do what you described.

Thanks Patmo,

I’ll try it as soon as i’m back on my computer. I wanted something build-in cause i don’t want to programme something that already exist and i think an API call is better than python because it calls a compiled C function, wich is so much efficienter. But i may be wrong.

For the distance, i was asking myself what error can be seen as a “float” error. I mean, even the cube after some rotation surely has not the 4 vertecies of his faces coplanar cause of approximation. Some more complexe workflow (many modifiers, rotation, scale…) could make that approximation error bigger.

How much should i put the treshold for error ? How many BU make it visible ?

Thanks again for your both answer (built-in and own function)

you need to add an acceptable error or margin for the calculations!

salutations

Yes and i don’t know what is acceptable

By the way, i had a look at the apidoc for 2.62, looks like it moved to mathutils.geometry from geometry_utils.

I’ll do some testing to see if it that built-in function already has an error margin.

Otherwise i must do 2 test per vertecies (>-margin or < margin because it can return a negative value) and for models with 1 Million vertecies, it could be way too long…

Certainly matali you are welcome. The “acceptable” threshold is going to depend a lot on what you are doing. When do you consider your bank account at zero? If you are buying a house, $1000 is practically zero, but if you are buying a stamp, then $0.01 is effectively zero. So, I would make the precision a variable in your function so you can adapt it. You may want to make it a “relative” precision. Eg, 10^-5 the length of AB in your ABC plane

got this from 2.49

can you port may be

i’ll try if i have the time later on this night or tomorrow

```
import bpy, Blender
from Blender.Mathutils import TriangleNormal
def isCoplanar(verts):
norm1 = TriangleNormal(verts[0].co, verts[1].co, verts[2].co)
norm2 = TriangleNormal(verts[1].co, verts[2].co, verts[3].co)
if 0.999999 < abs(norm1.dot(norm2)) < 1.000001:
return True
else:
return False
ob = bpy.data.objects['Cube']
me = ob.getData(mesh=True)
for f in me.faces:
if isCoplanar(f.verts):
print "Face "+str(f.index)+" is coplanar"
```

you could make the margin a var here !

thanks

I like that idea of the relativness to the ABC distances

By the way, could be great to speak in mm cm and m for that. How can i switch the metric system in my script ? I tried to copy the Ui function but it doesn’t work.

Thanks

print (‘UnitSettings.system =’, bpy.context.scene.unit_settings.system)

salutations

Works Thanks. And i didn’t see your post on the old 2.49 script. I’ll have a look to it and do some perf test compared to the build-in function if i’ve time.