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@HungryProton
Last active July 8, 2023 14:46
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Autosmooth meshes in GDScript
class_name MeshUtils
static func auto_smooth(mesh: Mesh, threshold_degrees := 30.0) -> Mesh:
var result := ArrayMesh.new()
var threshold := deg_to_rad(threshold_degrees)
var sanitized_mesh := merge_duplicate_vertices(mesh)
# Auto smooth each surfaces.
# If you need to auto smooth the whole mesh at once, merge all surfaces first.
for surface_index in sanitized_mesh.get_surface_count():
var mdt := MeshDataTool.new()
mdt.create_from_surface(sanitized_mesh, surface_index)
# Final arrays from where the mesh will be reconstructed
var vertices: Array[Vector3] = []
var normals: Array[Vector3] = []
var colors: Array[Color] = []
var indices: Array[int] = []
# Gather data about each faces
# ------
var vertex_map := {} # key: vertex id, value: array with face indices connected to the vertex.
var face_map := {} # key: face id, value: array with the 3 original vertex id
var new_face_map := {} # Same as face_map, but holds the new vertex id instead
for face_index in mdt.get_face_count():
if not face_index in face_map:
face_map[face_index] = []
for i in [0, 1, 2]: # 3 vertex per face
var original_vertex := mdt.get_face_vertex(face_index, i)
if not original_vertex in vertex_map:
vertex_map[original_vertex] = []
face_map[face_index].push_back(original_vertex)
vertex_map[original_vertex].push_back(face_index)
new_face_map = face_map.duplicate(true)
# Utility lambdas
# ------
# Returns the three edges indices associated with a face
var get_face_edges := func (face_index: int) -> Array[int]:
var edges : Array[int] = []
for i in [0, 1, 2]:
edges.push_back(mdt.get_face_edge(face_index, i))
return edges
# Returns true if both edges array contains at least one common edge with normals
# below the angle threshold
var has_common_soft_edges := func(edges_1: Array[int], edges_2: Array[int]) -> bool:
for edge_1 in edges_1:
for edge_2 in edges_2:
if edge_1 != edge_2:
continue
# One common edge found
var edge_faces := mdt.get_edge_faces(edge_1)
if edge_faces.size() != 2:
print_debug("Non manifold geometry detected. Can't handle this case.")
continue
# Compare normals
var normal_1 := mdt.get_face_normal(edge_faces[0]).normalized()
var normal_2 := mdt.get_face_normal(edge_faces[1]).normalized()
var angle := normal_1.angle_to(normal_2)
if angle < threshold:
return true # Soft edge found
# No soft edge found
return false
# Merge vertices together
# ------
for original_vertex in mdt.get_vertex_count():
# Get the faces touching this vertex
var parent_faces: Array[int] = []
parent_faces.assign(vertex_map[original_vertex])
var face_count: int = parent_faces.size()
var face_groups: Array = []
# Group together faces sharing common edges
# ------
var iterations := 0
while not parent_faces.is_empty():
# Pick a face not in a group yet
var p_face_1 := parent_faces.pop_front()
var edges_1 := get_face_edges.call(p_face_1)
# Either
# - First iteration, no existing groups yet
# - Too many iterations, remaining faces should move to their own group
if face_groups.is_empty() or iterations == parent_faces.size() + 1:
face_groups.push_back([p_face_1])
iterations = 0
continue
# Check against existing groups if it can fit
var fits_in_group := false
for group in face_groups:
for p_face_2 in group:
var edges_2 := get_face_edges.call(p_face_2)
if has_common_soft_edges.call(edges_1, edges_2):
group.push_back(p_face_1)
fits_in_group = true
break
if fits_in_group:
break
# Can't fit an existing group yet, add it to the back of the list
if not fits_in_group:
parent_faces.push_back(p_face_1)
iterations += 1
else:
iterations = 0
# For each group, average the faces normals and merge the vertices
# ------
for group in face_groups:
var normal := Vector3.ZERO
for face_index in group:
normal += mdt.get_face_normal(face_index)
var new_vertex_index := vertices.size()
vertices.push_back(mdt.get_vertex(original_vertex))
normals.push_back(normal.normalized())
for face_index in group:
var id: int = face_map[face_index].find(original_vertex)
new_face_map[face_index][id] = new_vertex_index
# Flatten the face map into a proper index array
for face_data in new_face_map.values():
for vertex_index in face_data:
indices.push_back(vertex_index)
## Recompose the mesh from the arrays above
var st := SurfaceTool.new()
st.begin(Mesh.PRIMITIVE_TRIANGLES)
st.set_smooth_group(0)
for i in vertices.size():
st.set_normal(normals[i])
st.add_vertex(vertices[i])
for index in indices:
st.add_index(index)
# Store the final result
result.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, st.commit_to_arrays())
return result
# Merge vertices sharing the same position into a single one.
# Normal data is not preserved and the resulting mesh will be smooth shaded.
static func merge_duplicate_vertices(mesh: Mesh) -> Mesh:
var result := ArrayMesh.new()
# Utility lambdas
var has_duplicate_values = func(array: Array) -> bool:
var size := array.size()
for i in size:
for j in range(i + 1, size):
if array[i] == array[j]:
return true
return false
# Apply to each individual surfaces
for surface_index in mesh.get_surface_count():
var mdt := MeshDataTool.new()
mdt.create_from_surface(mesh, surface_index)
# Final arrays from where the mesh will be reconstructed
var vertices: Array[Vector3] = []
var indices: Array[int] = []
# Create a map use to find the final merged vertex based on position alone
# Key: Vertex position, value: vertex index.
var vertex_map := {}
for vertex_index in mdt.get_vertex_count():
var vertex_pos := mdt.get_vertex(vertex_index)
if not vertex_pos in vertex_map:
var new_vertex_index = vertices.size()
vertices.push_back(vertex_pos)
vertex_map[vertex_pos] = new_vertex_index
# For each face, get the 3 vertices position and match them against the
# vertex map to find the actual vertices composing this face. Update
# indices accordingly
for face_index in mdt.get_face_count():
var new_face_indices: Array[int] = []
for i in [0, 1, 2]:
var vertex_index := mdt.get_face_vertex(face_index, i)
var vertex_pos := mdt.get_vertex(vertex_index)
new_face_indices.push_back(vertex_map[vertex_pos])
if has_duplicate_values.call(new_face_indices):
continue # Invalid triangle
for vertex_index in new_face_indices:
indices.push_back(vertex_index)
## Recreate the mesh from the arrays above
var st := SurfaceTool.new()
st.begin(Mesh.PRIMITIVE_TRIANGLES)
st.set_smooth_group(0)
for i in vertices.size():
st.add_vertex(vertices[i])
for index in indices:
st.add_index(index)
st.generate_normals()
# Store the final result
result.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, st.commit_to_arrays())
return result
@HungryProton
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Extra data (like colors, weight, UVs and so on) are NOT preserved, but should be easy enough to add.

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