feat: first séance
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134
src/main.py
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134
src/main.py
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import obja.obja
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import numpy as np
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import itertools
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def sliding_window(iterable, n=2):
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iterables = itertools.tee(iterable, n)
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for iterable, num_skipped in zip(iterables, itertools.count()):
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for _ in range(num_skipped):
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next(iterable, None)
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return zip(*iterables)
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class MAPS(obja.Model):
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"""
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A simple class that decimates a 3D model stupidly.
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"""
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def __init__(self):
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super().__init__()
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self.deleted_faces = set()
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def one_ring(self, index: int) -> list[int]:
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"""
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Return the vertex indices of the corresponding 1-ring.
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"""
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# Find the 1-ring faces
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ring_faces = []
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for face in enumerate(self.faces):
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if index in (face.a, face.b, face.c):
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ring_faces.append(face)
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# Initialize the ring
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start_index = ring_faces[0][0] if ring_faces[0][0] != index else ring_faces[0][1]
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ring = [start_index]
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ring_faces.pop(0)
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# Select the indexes of the ring in the right order
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while len(ring_faces) > 0:
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prev_index = ring[-1]
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for i, face in enumerate(ring_faces):
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if prev_index in (face.a, face.b, face.c):
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# if the previous index is in the current face
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current_index = (
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face.a if face.a != index and face.a != prev_index else
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face.b if face.b != index and face.b != prev_index else
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face.c
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)
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ring.append(current_index)
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ring_faces.pop(i)
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break
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return ring
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def compute_area_curvature(self, index: int) -> tuple[float, float]:
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area_sum = 0
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curvature_sum = 0
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one_ring_vertices = self.one_ring(index)
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p1 = self.vertices[index] # the center of the one-ring
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for index2, index3 in sliding_window(one_ring_vertices, 2):
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p2 = self.vertices[index2] # the second vertice of the triangle
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p3 = self.vertices[index3] # the third vertice of the triangle
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M = np.array([ # build the matrix, used to compute the area
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[p1[0], p2[0], p3[0]],
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[p1[1], p2[1], p3[1]],
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[p1[2], p2[2], p3[2]],
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])
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area = np.linalg.det(M) / 2 # compute the area
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area_sum += area
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curvature = 4 * area / ( # compute the curvature
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np.linalg.norm(p1-p2) * np.linalg.norm(p2-p3) * np.linalg.norm(p3-p1)
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)
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curvature_sum += curvature
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return area_sum, curvature_sum
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# def contract(self, output):
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# """
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# Decimates the model stupidly, and write the resulting obja in output.
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# """
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# operations = []
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# for (vertex_index, vertex) in enumerate(self.vertices):
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# operations.append(('ev', vertex_index, vertex + 0.25))
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# # Iterate through the vertex
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# for (vertex_index, vertex) in enumerate(self.vertices):
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# # Iterate through the faces
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# for (face_index, face) in enumerate(self.faces):
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# # Delete any face related to this vertex
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# if face_index not in self.deleted_faces:
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# if vertex_index in [face.a,face.b,face.c]:
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# self.deleted_faces.add(face_index)
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# # Add the instruction to operations stack
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# operations.append(('face', face_index, face))
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# # Delete the vertex
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# operations.append(('vertex', vertex_index, vertex))
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# # To rebuild the model, run operations in reverse order
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# operations.reverse()
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# # Write the result in output file
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# output_model = obja.Output(output, random_color=True)
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# for (ty, index, value) in operations:
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# if ty == "vertex":
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# output_model.add_vertex(index, value)
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# elif ty == "face":
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# output_model.add_face(index, value)
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# else:
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# output_model.edit_vertex(index, value)
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def main():
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"""
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Runs the program on the model given as parameter.
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"""
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model = MAPS()
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model.parse_file('example/suzanne.obj')
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# with open("example/suzanne.obja", "w") as output:
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# model.contract(output)
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if __name__ == '__main__':
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np.seterr(invalid = 'raise')
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main()
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