Detecting if a point is inside a mesh? 2.5 API

Coding Python Support
21

Restraining input meshes to have a euler characteristic of 2, will also block meshes that this algorithm can easily solve. Most simple example: two non intersecting cubes (EC = 4). E.g.

  +---------+   +---------+            +---------+ 
  |         |   |         |            |         |
  |         |   |         |            |  +---+  |
  |         |   |         |     or     |  |   |  |
  |         |   |         |            |  +---+  |  
  |         |   |         |            |         |  
  +---------+   +---------+            +---------+

You have a valid point, but you can’t expect an algorithm to take care of everything. Garbage in = Garbage out.

22

@ aothms - Geeeeezzz…

Dunno what is the result after applying the code above cause I havent tested it.

At these cases, although the mesh consists of 2 non-intersecting parts, each part has Euler result = 2, the correct algorithm based on the fact “counting ALL intersections of a ray at any direction and judging the point is INSIDE the body if they are an ODD number” will ALWAYS work cause for any point in INSIDE either body you will have n = 1 as a result. Thus, you’re correctly pointing out that the mesh should be processed first to defining its parts.

Regards,

23

I have put together a test file here to show how I plan on using the aothms code.
http://blenderartists.org/forum/showthread.php?p=1692253#post1692253

24

Apparently, there is a nice API function that tells you if a point is inside a mesh or not. Frankly, I didnt pay much attention to it by now. It’s use is rather simple and it may be like this:

sce = Scene.GetCurrent()
ob = Object.GetSelected()[0]
me = ob.getData(mesh=1)
mat = ob.mat
mat_inv = Mathutils.Matrix(mat).invert()
point = Mathutils.Vector(0,-2,2)
if me.pointInside(point*mat_inv):
  blah-blah-blah
  .................................

As per my testings, it works also in case your mesh consists of several parts.

Regards,

25

@abidos: Thanks for the 2.49 tip.

pointInside is exactly the function that I needed to replace in 2.5. It was not ported over or made available in the API…

26

do you have the 2.5 one
might be usefull later on!

and this works only for non manifod mesh !

but anythng available if you have some manifold mesh ?

Thanks

27

Hey Guys!
Someone port the code (pointInsideMesh) to Blender 2.6?

28

I need this also!
I still haven’t found a reliable way to do this.
I have one method, but it doesn’t always work.
Was that 2.49 version reliable?
If so, why isn’t it in the current release?

29

This thread helped me too. Thx to all for sharing. Here are my updated version (2.74). And a second approach by using closest_point_on_mesh method, but sometimes it seems to be unprecise.



def point_inside(point,obj):
    axes = [ Vector((1,0,0)), Vector((0,1,0)), Vector((0,0,1)) ]
    outside = False
    mat = obj.matrix_world.copy()
    mat.invert()
    for axis in axes:
        orig = mat*point
        count = 0
        while True:
            location,normal,index = obj.ray_cast(orig,orig+axis*1.84467e+19)
            if index == -1: break
            count += 1
            orig = location + axis*0.00001
        if count%2 == 0:
            outside = True
            break
    return not outside

def inside_to_closest_point(p, obj):
    inv = obj.matrix_world.copy()
    inv.invert()
    point, normal, face = obj.closest_point_on_mesh(inv*p, 1.84467e+19)
    return (point-inv*p).dot(normal) >= 0.0