CODEWITHSUNDEEP
python-3.x3d
MadPhysicist
MadPhysicist

Reputation: 195

Create a .stl file from a collection of points

So the software I am using accepts 3D objects in the form of contours or .stl files. The contours I have are along the z-plane(each plane has a unique z). I have had to modify the contours for my experiment and now the contours do not have a unique z for each plane(they are now slightly angled wrt z=0 plane).

The points represent the edges of the 3D object. What would be the best way to take this collection of points and create a .stl file?

I am relatively new to working with python and 3D objects, so any help, pointers or suggestions would be much appreciated.

Edit: I have the simplices and verticies using the Delaunay(), but how do I proceed next?

  1. The co-ordinates of all points are in this text file in the format "x y z".

Upvotes: 5

Views: 13702

Answers (2)

vpathak
vpathak

Reputation: 1163

I noticed the numpy-stl answer and while that library seems to work for the initial basic stuff, it seems to get out of hand easily. Particularly because of the low documentation quality.

A simpler more robust approach is to use solid python and then export it to scad format. This is for the openscad tool which makes it quite easy to mathematically generate and manipulate 3d objects. The icing on the cake is thats its well documented and efficient. And large number of basic things can be done out of the box by the solid python library in very readable and maintainable manner

While its a great thought that numpy is being used to manipulate stl - and so the performance is great - it still suffers from significant usability issues. That you used numpy to make your library should not be the USP - but looks like it is.

Nothing against the library or the authors. Just that it seems to be more of a hack than a scalable usable complete solution - and I had to learn it the hard way.

Try solid python and openscad even though the numpy stl marketing lines are quite tempting.

Upvotes: 0

MadPhysicist
MadPhysicist

Reputation: 195

So after seeking an answer for months and trying to use Meshlab and Blender I finally stumbled across the answer using numpy-stl. Hopeful that it will help others in a similar situation.

Here is the code to generate the .STL file:

from stl import mesh
num_triangles=len(fin_list)
data = np.zeros(num_triangles, dtype=mesh.Mesh.dtype)
for i in range(num_triangles):
    #I did not know how to use numpy-arrays in this case. This was the major roadblock
    # assign vertex co-ordinates to variables to write into mesh
    data["vectors"][i] = np.array([[v1x, v1y, v1z],[v2x, v2y, v2z],[v3x, v3y, v3z]])
m=mesh.Mesh(data)
m.save('filename.stl')

The three vertices that form a triangle in the mesh go in as a vector that define the surface normal. I just collected three such vertices that form a triangle and wrote them into the mesh. Since I had a regular array of points, it was easy to collect the triangles:

for i in range(len(point_list)-1):
        plane_a=[]
        plane_b=[]
        for j in range(len(point_list[i])-1):
            tri_a=[]
            tri_b=[]
            #series a triangles
            tri_a.append(point_list[i+1][j])
            tri_a.append(point_list[i][j+1])
            tri_a.append(point_list[i][j])
            #series b triangles
            tri_b.append(point_list[i+1][j])
            tri_b.append(point_list[i+1][j+1])
            tri_b.append(point_list[i][j+1])
            #load to plane
            plane_a.append(tri_a)
            plane_b.append(tri_b)
        group_a.append(plane_a)
        group_b.append(plane_b)

The rules for choosing triangles for creating a mesh are as follows:

  1. The vertices must be arranged in a counter-clock direction.
  2. Each triangle must share two vertices with adjacent triangles.
  3. The direction normal must point out of the surface.

There were two more rules that I did not follow but it still worked in my case: 1. All coordinates must be positive(In 1st Quadrant only) 2. All triangles must be arranged in an increasing z-order.

Note: There can be two kinds of .STL file formats: Binary and ASCII. numpy-stl writes out in the binary format. More info on STL files can be found here.

Hope this helps!

Upvotes: 10

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