Plot3D Data Format
====================
Data format for plot3D comes from this 1990s manual :download:`pdf <../_static/plot3d_manual.pdf>` Plot3D is a simple way to construct a structured grid using 4 points to define a cell in 2D and 8 points for 3D.
Plot3D files are organized as follows
.. code-block:: text
:linenos:
8 # Number of blocks
5 5 5 # Block 1 is shaped 5x5x5 in i,j,k this is 125 nodes
5 5 5 # Block 2 shape
5 5 5
5 5 5
5 5 5
5 5 5
5 5 5
5 5 5
1.08569236018e-07 2.89960779720e-07 2.99150448968e-07 2.55513369907e-07 # First 125 values describe are X, next 25 are Y, last 25 are Z
2.12244548714e-07 1.01483086157e-07 2.67218012828e-07 2.71062573276e-07
2.24420893535e-07 1.78210401103e-07 7.47886754748e-08 1.93926065872e-07
1.84719158858e-07 1.38925249638e-07 1.00523800506e-07 1.71518139691e-08
9.37154616132e-08 9.36074304736e-08 5.80944219397e-08 2.00380892990e-08
-5.46866818496e-08 -1.24404013757e-08 1.15859071226e-08 -4.76059469623e-09
Knowing this, reading the files is fairly simple to do in python. The following code blocks demonstrate how to read a simple ASCII or binary file. Calling the function ``read_plot3D(filename:str, binary:bool=True,big_endian:bool=False)``
.. code-block:: python
:linenos:
import numpy as np
import os.path as osp
import struct
from typing import List
from .block import Block
def __read_plot3D_chunk_binary(f,IMAX:int,JMAX:int,KMAX:int, big_endian:bool=False):
"""Reads and formats a binary chunk of data into a plot3D block
Args:
f (io): file handle
IMAX (int): maximum I index
JMAX (int): maximum J index
KMAX (int): maximum K index
big_endian (bool, Optional): Use big endian format for reading binary files. Defaults False.
Returns:
numpy.ndarray: Plot3D variable either X,Y, or Z
"""
A = np.empty(shape=(IMAX, JMAX, KMAX))
for k in range(KMAX):
for j in range(JMAX):
for i in range(IMAX):
A[i,j,k] = struct.unpack(">f",f.read(4))[0] if big_endian else struct.unpack("f",f.read(4))[0]
return A
def __read_plot3D_chunk_ASCII(tokenArray:List[str],offset:int,IMAX:int,JMAX:int,KMAX:int):
"""Reads an ascii chunk of plot3D data into a block
Args:
tokenArray (List[str]): this is a list of strings separated by a space, new line character removed ["12","22", ... etc]
offset (int): how many entries to skip in the array based on block size (IMAX*JMAX*KMAX) of the previous block
IMAX (int): maximum I index
JMAX (int): maximum J index
KMAX (int): maximum K index
Returns:
numpy.ndarray: Plot3D variable either X,Y, or Z
"""
'''Works for ASCII files
'''
A = np.empty(shape=(IMAX, JMAX, KMAX))
for k in range(KMAX):
for j in range(JMAX):
for i in range(IMAX):
A[i,j,k] = tokenArray[offset]
offset+=1
return A, offset
def read_plot3D(filename:str, binary:bool=True,big_endian:bool=False):
"""Reads a plot3d file and returns Blocks
Args:
filename (str): name of the file to read, .p3d, .xyz, .pdc, .plot3d?
binary (bool, optional): indicates if the file is binary. Defaults to True.
big_endian (bool, optional): use big endian format for reading binary files
Returns:
List[Block]: List of blocks insdie the plot3d file
"""
blocks = list()
if osp.isfile(filename):
if binary:
with open(filename,'rb') as f:
nblocks = struct.unpack(">I",f.read(4))[0] if big_endian else struct.unpack("I",f.read(4))[0] # Read bytes
IMAX = list(); JMAX = list(); KMAX = list()
for b in range(nblocks):
if big_endian:
IMAX.append(struct.unpack(">I",f.read(4))[0]) # Read bytes
JMAX.append(struct.unpack(">I",f.read(4))[0]) # Read bytes
KMAX.append(struct.unpack(">I",f.read(4))[0]) # Read bytes
else:
IMAX.append(struct.unpack("I",f.read(4))[0]) # Read bytes
JMAX.append(struct.unpack("I",f.read(4))[0]) # Read bytes
KMAX.append(struct.unpack("I",f.read(4))[0]) # Read bytes
for b in range(nblocks):
X = __read_plot3D_chunk_binary(f,IMAX[b],JMAX[b],KMAX[b], big_endian)
Y = __read_plot3D_chunk_binary(f,IMAX[b],JMAX[b],KMAX[b], big_endian)
Z = __read_plot3D_chunk_binary(f,IMAX[b],JMAX[b],KMAX[b], big_endian)
b_temp = Block(X,Y,Z)
blocks.append(b_temp)
else:
with open(filename,'r') as f:
nblocks = int(f.readline())
IMAX = list(); JMAX = list(); KMAX = list()
for b in range(nblocks):
tokens = [int(w.replace('\n','')) for w in f.readline().split(' ') if w]
IMAX.append(tokens[0])
JMAX.append(tokens[1])
KMAX.append(tokens[2])
lines = [l.replace('\n','').split(' ') for l in f.readlines()] # Basically an array of strings representing numbers
lines = [item for sublist in lines for item in sublist] # Flatten list of lists https://stackabuse.com/python-how-to-flatten-list-of-lists/
tokenArray = [float(entry) for entry in lines if entry] # Convert everything to float
offset = 0
for b in range(nblocks):
X, offset = __read_plot3D_chunk_ASCII(tokenArray,offset,IMAX[b],JMAX[b],KMAX[b])
Y, offset = __read_plot3D_chunk_ASCII(tokenArray,offset,IMAX[b],JMAX[b],KMAX[b])
Z, offset = __read_plot3D_chunk_ASCII(tokenArray,offset,IMAX[b],JMAX[b],KMAX[b])
b_temp = Block(X,Y,Z)
blocks.append(b_temp)
return blocks