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import codecs |
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import hashlib |
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from maya.api import OpenMaya as om |
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class _C4Hasher(object): |
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CHUNK_SIZE = 4096 * 10 # magic number |
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PREFIX = "c4" |
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def __init__(self): |
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self.hash_obj = None |
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self.clear() |
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def clear(self): |
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"""Start a new hash session |
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""" |
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self.hash_obj = hashlib.sha512() |
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def _b58encode(self, bytes): |
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"""Base58 Encode bytes to string |
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""" |
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b58chars = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz" |
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b58base = 58 |
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long_value = int(codecs.encode(bytes, "hex_codec"), 16) |
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result = "" |
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while long_value >= b58base: |
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div, mod = divmod(long_value, b58base) |
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result = b58chars[mod] + result |
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long_value = div |
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result = b58chars[long_value] + result |
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return result |
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def digest(self): |
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"""Return hash value of data added so far |
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""" |
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c4_id_length = 90 |
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b58_hash = self._b58encode(self.hash_obj.digest()) |
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padding = "" |
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if len(b58_hash) < (c4_id_length - 2): |
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padding = "1" * (c4_id_length - 2 - len(b58_hash)) |
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c4id = self.PREFIX + padding + b58_hash |
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return c4id |
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class MeshHasher(object): |
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"""A mesh geometry hasher for Maya |
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For quickly identifying if any change on vertices, normals and UVs. |
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Hash value will be encoded as Avalanche-io C4 Asset ID. |
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Order matters, transform does not. |
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Example Usage: |
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>> hasher = MeshHasher() |
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>> hasher.set_mesh("path|to|mesh") |
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>> hasher.update_points() |
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>> hasher.update_normals() |
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>> hasher.update_uvmap() |
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>> hasher.digest() |
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{'normals': 'c41MSCnAGqWS9dBDDpydbpcMwzzFkGH66jNpuTqctfY...', |
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'points': 'c44fV5wa6bNiekUadZ4HsRPDL2HZ11RFKcXhf3pntsUJ...', |
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'uvmap': 'c45JRQTPxgMNYfcijAbm31vkJRt6CUUSn7ew2X1Mnyjwi...'} |
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Hash meshes in loop |
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>> for mesh in cmds.ls(type="mesh", ni=Ture, long=True) |
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... hasher.set_mesh(mesh) |
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... hasher.update_points() |
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... hasher.update_normals() |
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... |
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>> hasher.digest() |
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{'normals': 'c456rBNH5pzobqjHzFnHApanrTdJo64r2R8o4GJxqU9G...', |
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'points': 'c449wXhjNSSKfnUjPp2ub3fd1DeNowW2x5gBJDYrSvxrT...'} |
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You can still adding more meshes until you call `clear` |
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>> hasher.clear() |
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""" |
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def __init__(self): |
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self.clear() |
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def clear(self): |
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self._mesh = None |
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self._points = 0 |
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self._normals = 0 |
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self._uvmap = 0 |
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def set_mesh(self, dag_path): |
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"""Set one mesh geometry node to hasher |
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Arguments: |
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dag_path (str): Mesh node's DAG path |
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""" |
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sel_list = om.MSelectionList() |
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sel_list.add(dag_path) |
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sel_obj = sel_list.getDagPath(0) |
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self._mesh = om.MFnMesh(sel_obj) |
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def update_points(self): |
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for i, vt in enumerate(self._mesh.getPoints()): |
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self._points += _hash_MPoint(*vt) + i |
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def update_normals(self): |
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for i, vt in enumerate(self._mesh.getNormals()): |
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self._normals += _hash_MFloatVectors(*vt) + i |
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def update_uvmap(self, uv_set=""): |
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for i, uv in enumerate(zip(*self._mesh.getUVs(uv_set))): |
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self._uvmap += _hash_UV(*uv) + i |
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def digest(self): |
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result = dict() |
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hasher = _C4Hasher() |
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if self._points: |
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hasher.hash_obj.update(str(self._points)) |
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result["points"] = hasher.digest() |
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hasher.clear() |
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if self._normals: |
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hasher.hash_obj.update(str(self._normals)) |
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result["normals"] = hasher.digest() |
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hasher.clear() |
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if self._uvmap: |
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hasher.hash_obj.update(str(self._uvmap)) |
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result["uvmap"] = hasher.digest() |
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hasher.clear() |
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return result |
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# these are just hashing with magic numbers.. |
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def _hash_MPoint(x, y, z, w): |
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x = (x + 1) * 233 |
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y = (y + x) * 239 |
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z = (z + y) * 241 |
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return (x + y + z) * w |
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def _hash_MFloatVectors(x, y, z): |
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x = (x + 1) * 383 |
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y = (y + x) * 389 |
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z = (z + y) * 397 |
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return x + y + z |
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def _hash_UV(u, v): |
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u = (u + 1) * 547 |
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v = (v + u) * 557 |
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return u * v |
