Учитывая, что нет возможности указать ограничивающую рамку в Reality Capture API, я создал эту программу на Python. Это грубый метод, поскольку отбрасываются только грани, вершины которых находятся за пределами ограничивающего прямоугольника. И на самом деле он отбрасывает неразрушающим образом, только комментируя их в выходном файле OBJ. Это позволяет вам раскомментировать их, а затем использовать другую ограничивающую рамку.
Это может быть не то, что вам нужно, если вы действительно хотите удалить все соответствующие строки v, vn, vt, vp и f, которые находятся за пределами ограничивающей рамки, потому что размер файла OBJ остается в основном неизменным. Но для моих конкретных нужд предпочтительнее было вести все записи и просто использовать комментарии.
# obj3Dcrop.py
# (c) Scott L. McGregor, Dec 2019
# License: free for all non commercial uses. Contact author for any other uses.
# Changes and Enhancements must be shared with author, and be subject to same use terms
# TL;DR: This program uses a bounding box, and "crops" faces and vertices from a
# Wavefront .OBJ format file, created by Autodesk Forge Reality Capture API
# if one of the vertices in a face is not within the bounds of the box.
#
# METHOD
# 1) All lines other than "v" vertex definitions and "f" faces definitions
# are copied UNCHANGED from the input .OBJ file to an output .OBJ file.
# 2) All "v" vertex definition lines have their (x, y, z) positions tested to see if:
# minX < x < maxX and minY < y < maxY and minZ < z < maxZ ?
# If TRUE, we want to keep this vertex in the new OBJ, so we
# store its IMPLICIT ORDINAL position in the file in a dictionary called v_keepers.
# If FALSE, we will use its absence from the v_keepers file as a way to identify
# faces that contain it and drop them. All "v" lines are also copied unchanged to the
# output file.
# 3) All "f" lines (face definitions) are inspected to verify that all 3 vertices in the face
# are in the v_keepers list. If they are, the f line is output unchanged.
# 4) Any "f" line that refers to a vertex that was cropped, is prefixed by "# CROPPED: "
# in the output file. Lines beginning # are treated as comments, and ignored in future
# processing.
# KNOWN LIMITATIONS: This program generates models in which the outside of bound faces
# have been removed. The vertices that were found outside the bounding box, are still in the
# OBJ file, but they are now disconnected and therefore ignored in later processing.
# The "f" lines for faces with vertices outside the bounding box are also still in the
# output file, but now commented out, so they don't process. Because this is non-destructive.
# we can easily change our bounding box later, uncomment cropped lines and reprocess.
#
# This might be an incomplete solution for some potential users. For such users
# a more complete program would delete unneeded v, vn, vt and vp lines when the v vertex
# that they refer to is dropped. But note that this requires renumbering all references to these
# vertice definitions in the "f" face definition lines. Such a more complete solution would also
# DISCARD all 'f' lines with any vertices that are out of bounds, instead of making them copies.
# Such a rewritten .OBJ file would be var more compact, but changing the bounding box would require
# saving the pre-cropped original.
# QUIRK: The OBJ file format defines v, vn, vt, vp and f elements by their
# IMPLICIT ordinal occurrence in the file, with each element type maintaining
# its OWN separate sequence. It then references those definitions EXPLICITLY in
# f face definitions. So deleting (or commenting out) element references requires
# appropriate rewriting of all the"f"" lines tracking all the new implicit positions.
# Such rewriting is not particularly hard to do, but it is one more place to make
# a mistake, and could make the algorithm more complicated to understand.
# This program doesn't bother, because all further processing of the output
# OBJ file ignores unreferenced v, vn, vt and vp elements.
#
# Saving all lines rather than deleting them to save space is a tradeoff involving considerations of
# Undo capability, compute cycles, compute space (unreferenced lines) and maintenance complexity choice.
# It is left to the motivated programmer to add this complexity if needed.
import sys
#bounding_box = sys.argv[1] # should be in the only string passsed (maxX, maxY, maxZ, minX, minY, minZ)
bounding_box = [10, 10, 10, -10, -10, 1]
maxX = bounding_box[0]
maxY = bounding_box[1]
maxZ = bounding_box[2]
minX = bounding_box[3]
minY = bounding_box[4]
minZ = bounding_box[5]
v_keepers = dict() # keeps track of which vertices are within the bounding box
kept_vertices = 0
discarded_vertices = 0
kept_faces = 0
discarded_faces = 0
discarded_lines = 0
kept_lines = 0
obj_file = open('sample.obj','r')
new_obj_file = open('cropped.obj','w')
# the number of the next "v" vertex lines to process.
original_v_number = 1 # the number of the next "v" vertex lines to process.
new_v_number = 1 # the new ordinal position of this vertex if out of bounds vertices were discarded.
for line in obj_file:
line_elements = line.split()
# Python doesn't have a SWITCH statement, but we only have three cases, so we'll just use cascading if stmts
if line_elements[0] != "f": # if it isn't an "f" type line (face definition)
if line_elements[0] != "v": # and it isn't an "v" type line either (vertex definition)
# ************************ PROCESS ALL NON V AND NON F LINE TYPES ******************
# then we just copy it unchanged from the input OBJ to the output OBJ
new_obj_file.write(line)
kept_lines = kept_lines + 1
else: # then line_elements[0] == "v":
# ************************ PROCESS VERTICES ****************************************
# a "v" line looks like this:
# f x y z ...
x = float(line_elements[1])
y = float(line_elements[2])
z = float(line_elements[3])
if minX < x < maxX and minY < y < maxY and minZ < z < maxZ:
# if vertex is within the bounding box, we include it in the new OBJ file
new_obj_file.write(line)
v_keepers[str(original_v_number)] = str(new_v_number)
new_v_number = new_v_number + 1
kept_vertices = kept_vertices +1
kept_lines = kept_lines + 1
else: # if vertex is NOT in the bounding box
new_obj_file.write(line)
discarded_vertices = discarded_vertices +1
discarded_lines = discarded_lines + 1
original_v_number = original_v_number + 1
else: # line_elements[0] == "f":
# ************************ PROCESS FACES ****************************************
# a "f" line looks like this:
# f v1/vt1/vn1 v2/vt2/vn2 v3/vt3/vn3 ...
# We need to delete any face lines where ANY of the 3 vertices v1, v2 or v3 are NOT in v_keepers.
v = ["", "", ""]
# Note that v1, v2 and v3 are the first "/" separated elements within each line element.
for i in range(0,3):
v[i] = line_elements[i+1].split('/')[0]
# now we can check if EACH of these 3 vertices are in v_keepers.
# for each f line, we need to determine if all 3 vertices are in the v_keepers list
if v[0] in v_keepers and v[1] in v_keepers and v[2] in v_keepers:
new_obj_file.write(line)
kept_lines = kept_lines + 1
kept_faces = kept_faces +1
else: # at least one of the vertices in this face has been deleted, so we need to delete the face too.
discarded_lines = discarded_lines + 1
discarded_faces = discarded_faces +1
new_obj_file.write("# CROPPED "+line)
# end of line processing loop
obj_file.close()
new_obj_file.close()
print ("kept vertices: ", kept_vertices ,"discarded vertices: ", discarded_vertices)
print ("kept faces: ", kept_faces, "discarded faces: ", discarded_faces)
print ("kept lines: ", kept_lines, "discarded lines: ", discarded_lines)
person
mcgregor94086
schedule
18.12.2019
