No displacement or deformation after simulation in python polyfem

Question

I've been trying to get material deformation for a while in python polyfem, and it just doesn't happen.

As far as I know, it should just works. The examples and docs says it return a deformation , but when I check its min and max, it'S 0 no matter what I do. I just don't understand why.

Here's some example code to create a square grid mesh:

import numpy as np
import meshio
import polyscope as ps

# Define grid dimensions
n = 10

# Create vertices for a grid of (n x n) squares
vertices = []
for i in range(n + 1):
    for j in range(n + 1):
        vertices.append([i / n, j / n, 0])

vertices = np.array(vertices, dtype=np.float32)

# Create faces (triangles) for each square
faces = []
k = 0
for i in range(n):
    for j in range(n):
        # Indices of the vertices for the current square
        v0 = i * (n + 1) + j
        v1 = v0 + 1
        v2 = v0 + (n + 1)
        v3 = v2 + 1
        center = (vertices[v0]+vertices[v1]+vertices[v2]+vertices[v3])/4
        
        print(k, center)
                
        
        # First triangle
        faces.append([v0, v1, v2])
        # Second triangle
        faces.append([v1, v3, v2])
        k+=2



faces = np.array(faces, dtype=np.int32)

# Save to OBJ file using meshio
mesh = meshio.Mesh(points=vertices, cells=[("triangle", faces)])
meshio.write("grid_mesh.obj", mesh)

# Initialize Polyscope
ps.init()

# Load the mesh from the OBJ file
mesh = meshio.read("grid_mesh.obj")

# Extract vertices and faces
vertices = mesh.points
faces = mesh.cells_dict["triangle"]

# Register the mesh with Polyscope
ps_mesh = ps.register_surface_mesh("2D Grid", vertices, faces)

# Show the mesh
ps.show()

and some static deformation code:

import numpy as np
import meshio
import polyscope as ps

# Define grid dimensions
n = 10

# Create vertices for a grid of (n x n) squares
vertices = []
for i in range(n + 1):
    for j in range(n + 1):
        vertices.append([i / n, j / n, 0])

vertices = np.array(vertices, dtype=np.float32)

# Create faces (triangles) for each square
faces = []
k = 0
for i in range(n):
    for j in range(n):
        # Indices of the vertices for the current square
        v0 = i * (n + 1) + j
        v1 = v0 + 1
        v2 = v0 + (n + 1)
        v3 = v2 + 1
        center = (vertices[v0]+vertices[v1]+vertices[v2]+vertices[v3])/4
        
        print(k, center)
                
        
        # First triangle
        faces.append([v0, v1, v2])
        # Second triangle
        faces.append([v1, v3, v2])
        k+=2



faces = np.array(faces, dtype=np.int32)

# Save to OBJ file using meshio
mesh = meshio.Mesh(points=vertices, cells=[("triangle", faces)])
meshio.write("grid_mesh.obj", mesh)

# Initialize Polyscope
ps.init()

# Load the mesh from the OBJ file
mesh = meshio.read("grid_mesh.obj")

# Extract vertices and faces
vertices = mesh.points
faces = mesh.cells_dict["triangle"]

# Register the mesh with Polyscope
ps_mesh = ps.register_surface_mesh("2D Grid", vertices, faces)

# Show the mesh
ps.show()