combine two stl into one

I have two 3D geometries ('sol_1.stl' and 'sol_2.stl') and their corresponding nodes and faces.

I would like to combine the two STL geometries into a single geometry, or merge the nodes and faces of the two geometries into one.

• sol_1.st + sol_2.st -> sol_fin.stl
• nodes_sol_1 + nodes_sol_2 -> nodes_sol_fin (simple)
• faces_sol_1 + faces_sol_2 -> faces_sol_fin

Answer 1

[Avni Agrawal]

Hi @Alberto Acri,

I understand that you are trying to combine two STL geometries into a single geometry by merging their nodes and faces in MATLAB, you can follow these steps:

1. Read the STL files to get the nodes and faces.
2. Merge the nodes and faces from both geometries.
3. Write the combined geometry to a new STL file.

Below is a MATLAB script that demonstrates how to do this:

% Read the STL files
fv1 = stlread('../sol/sol_1.stl');
fv2 = stlread('../sol/sol_2.stl');

% Extract nodes (vertices) and faces from the first geometry
nodes1 = fv1.Points;
faces1 = fv1.ConnectivityList;

% Extract nodes (vertices) and faces from the second geometry
nodes2 = fv2.Points;
faces2 = fv2.ConnectivityList;

% Merge nodes
% Note: We need to adjust the face indices of the second geometry
% by adding the number of nodes in the first geometry

% Combine nodes
combinedNodes = [nodes1; nodes2];

% Adjust face indices for the second geometry
adjustedFaces2 = faces2 + size(nodes1, 1);

% Combine faces
combinedFaces = [faces1; adjustedFaces2];

% Create a new triangulation object for the combined geometry
combinedGeometry = triangulation(combinedFaces, combinedNodes);

% Write the combined geometry to a new STL file
stlwrite(combinedGeometry, 'combined_geometry.stl');

I hope this helps.

[DGM]

Note that this doesn't actually do any CSG to combine the geometry (e.g. the union). This just creates a model with two independent connected components.

If the objects intersect, there will be no new vertices or edges formed at their intersection, and the model will have interior and/or tangential faces and edges.