Add obj_trimmer.py script for trimming obj files used for printer base plates.

CURA-7541

scripts/obj_trimmer.py

@@ -0,0 +1,130 @@
+# Copyright (c) 2022 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+import argparse
+import os
+from typing import Optional, List
+
+"""
+    Used to reduce the size of obj files used for printer platform models.
+    
+    Trims trailing 0 from coordinates
+    Removes duplicate vertex texture coordinates
+    Removes any rows that are not a face, vertex or vertex texture
+"""
+
+def process_obj(input_file, output_file):
+    with open(input_file, "r") as in_obj, open("temp", "w") as temp:
+        trim_lines(in_obj, temp)
+
+    with open("temp", "r") as temp, open(output_file, "w") as out_obj:
+        merge_duplicate_vt(temp, out_obj)
+
+    os.remove("temp")
+
+
+def trim_lines(in_obj, out_obj):
+    for line in in_obj:
+        line = trim_line(line)
+        if line:
+            out_obj.write(line + "\n")
+
+
+def trim_line(line: str) -> Optional[str]:
+    # Discards all rows that are not a vertex ("v"), face ("f") or vertex texture ("v")
+    values = line.split()
+
+    if values[0] == "vt":
+        return trim_vertex_texture(values)
+    elif values[0] == "f":
+        return trim_face(values)
+    elif values[0] == "v":
+        return trim_vertex(values)
+
+    return
+
+
+def trim_face(values: List[str]) -> str:
+    # Removes face normals (vn)
+    # f 15/15/17 15/15/17 14/14/17 -> f 15/15 15/15 14/14
+    for i, coordinates in enumerate(values[1:]):
+        v, vt = coordinates.split("/")[:2]
+        values[i + 1] = v + "/" + vt
+
+    return " ".join(values)
+
+
+def trim_vertex(values: List[str]) -> str:
+    # Removes trailing zeros from vertex coordinates
+    # v 0.044000 0.137000 0.123000 -> v 0.044 0.137 0.123
+    for i, coordinate in enumerate(values[1:]):
+        values[i + 1] = str(float(coordinate))
+    return " ".join(values)
+
+
+def trim_vertex_texture(values: List[str]) -> str:
+    # Removes trailing zeros from vertex texture coordinates
+    # vt 0.137000 0.123000 -> v 0.137 0.123
+    for i, coordinate in enumerate(values[1:]):
+        values[i + 1] = str(float(coordinate))
+    return " ".join(values)
+
+def merge_duplicate_vt(in_obj, out_obj):
+    # Removes duplicate vertex texture ("vt")
+    # Points references to all deleted copies in face ("f") to a single vertex texture
+
+    # Maps index of all copies of a vt line to the same index
+    vt_index_mapping = {}
+    # Maps vt line to index ("vt 0.043 0.137" -> 23)
+    vt_to_index = {}
+
+    # .obj file indexes start at 1
+    vt_index = 1
+    skipped_count = 0
+
+    # First write everything except faces
+    for line in in_obj.readlines():
+        if line[0] == "f":
+            continue
+
+        if line[:2] == "vt":
+            if line in vt_to_index.keys():
+                # vt with same value has already been written
+                # this points the current vt index to the one that has been written
+                vt_index_mapping[vt_index] = vt_to_index[line]
+                skipped_count += 1
+            else:
+                # vt has not been seen, point vt line to index
+                vt_to_index[line] = vt_index - skipped_count
+                vt_index_mapping[vt_index] = vt_index - skipped_count
+                out_obj.write(line)
+
+            vt_index += 1
+        else:
+            out_obj.write(line)
+
+    # Second pass remaps face vt index
+    in_obj.seek(0)
+    for line in in_obj.readlines():
+        if line[0] != "f":
+            continue
+
+        values = line.split()
+
+        for i, coordinates in enumerate(values[1:]):
+            v, vt = coordinates.split("/")[:2]
+            vt = int(vt)
+
+            if vt in vt_index_mapping.keys():
+                vt = vt_index_mapping[vt]
+
+            values[i + 1] = v + "/" + str(vt)
+
+        out_obj.write(" ".join(values) + "\n")
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Reduce the size of a .obj file")
+    parser.add_argument("input_file", type=str, help="Input .obj file name")
+    parser.add_argument("--output_file", default="output.obj", type=str, help="Output .obj file name")
+    args = parser.parse_args()
+    process_obj(args.input_file, args.output_file)