Here is my code: import ezdxf import numpy as np x,y = np.meshgrid(range(-3,3),range(-3,3)) z = x**2 + y**2 doc = ezdxf.new('R2010', setup=True) # Add a mesh entity msp = doc.modelspace() rows, cols = z.shape # Add a MESH entity mesh = msp.add_mesh() msp.doc.layers.add("3d_surface") mesh = msp.add_mesh(dxfattribs={"layer": "3d_surface"}) with mesh.edit_data() as mesh_data: # Create vertices from X, Y, and dem_data (Z) for i in range(rows): for j in range(cols): mesh_data.vertices.append((x[i, j], y[i, j], z[i, j])) # Create faces (each grid cell becomes a quadrilateral face) for i in range(rows - 1): for j in range(cols - 1): # Vertex indices for the four corners of the grid cell v0 = i * cols + j # Top-left v1 = v0 + 1 # Top-right v2 = v0 + cols # Bottom-left v3 = v2 + 1 # Bottom-right # Add a quadrilateral face mesh_data.faces.append((v0, v1, v3, v2)) dxf_file_path = 'example.dxf' doc.saveas(dxf_file_path) The created file can be read correctly by edrawings and on sharecad.org but not by freecad or autodesk. Autodesk viewer gives the following: AutoCAD-InvalidFile Sorry, the drawing file is invalid and cannot be viewed. - Please try to recover the file in AutoCAD, and upload it again to view. TranslationWorker-InternalFailure Unrecoverable exit code from extractor: -1073741831 Am I doing something wrong? Continue reading...