VTKfileformats资源-CSDN文库

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VTK (Visualization Toolkit) 文件格式是专为可视化和分析复杂数据集设计的一种数据表示方案，由Kitware开发并维护。这些格式旨在提供一种统一的数据表示方法，适用于多种数据集类型，并简化不同软件间的数据通信。虽然VTK推荐使用更广泛接受的格式，但在无法使用这些通用格式时，VTK自己的格式提供了替代方案。值得注意的是，VTK格式可能不会被许多其他工具所支持。在VTK中，存在两种不同的文件格式风格：简单的遗留格式和基于XML的格式。遗留格式易于手工或程序化读写，而XML格式则提供了更高的灵活性，支持随机访问、并行I/O以及便携式数据压缩。因此，在可能的情况下，XML格式更受推荐。 ### 简单的遗留格式 #### 文件结构遗留VTK文件格式由五个基本部分组成： 1. **文件版本与标识符**：文件的第一行必须是`# vtk DataFile Version x.x`，其中版本号`x.x`会随着VTK的不同发布版本而变化。当前的版本号是3.0，版本1.0和2.0的文件与3.0版本兼容。 2. **头信息**：接下来是头信息部分，它由一个以换行符`\n`终止的字符串构成，最大长度为256个字符。这部分可以用于描述数据集，包括任何相关的元数据。 3. **文件格式**：然后，文件会指定其格式类型，即ASCII或二进制。这一行只能包含单词"ASCII"或"BINARY"。 4. **数据集结构**：这部分描述了数据集的几何和拓扑结构。它以包含关键字`DATASET`的行开始，后面跟着描述数据集类型的关键词。根据数据集的类型，后续的关键词/数据组合定义了数据集的具体结构。 5. **数据本身**：文件包含了实际的数据，这些数据根据前文指定的格式（ASCII或二进制）进行编码。 ### XML格式 XML格式比遗留格式更灵活，它们支持随机访问、并行I/O和便携式数据压缩。这些格式通常更适合大型数据集和高性能计算环境。XML格式使用XML标记语言来描述数据结构，这使得数据格式更加标准化且易于解析。 ### 总结 VTK文件格式的设计是为了满足科学可视化和数据分析的需求。无论是简单的遗留格式还是功能更强大的XML格式，VTK都提供了丰富的工具和资源来处理复杂的数据集。对于需要跨平台和跨软件共享数据的用户来说，VTK格式提供了一种有效的解决方案，尤其是在其他通用格式不适用的情况下。然而，由于其特定性，VTK格式的使用可能受到一些第三方工具的支持限制。因此，在选择数据格式时，用户应考虑到其应用范围和兼容性需求。

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File Formats

for VTK Version 4.2

(Taken from The VTK User’s Guide

Contact Kitware www.kitware.com to purchase)

VTK File Formats

The Visualization Toolkit provides a number of source and writer objects to read and write popular data file formats. The

Visualization Toolkit also provides some of its own file formats. The main reason for creating yet another data file format

is to offer a consistent data representation scheme for a variety of dataset types, and to provide a simple method to com-

municate data between software. Whenever possible, we recommend that you use formats that are more widely used. But

if this is not possible, the Visualization Toolkit formats described here can be used instead. Note that these formats may not

be supported by many other tools.

There are two different styles of file formats available in VTK. The simplest are the legacy, serial formats that are

easy to read and write either by hand or programmatically. However, these formats are less flexible than the XML based

file formats described later in this section. The XML formats support random access, parallel I/O, and portable data com-

pression and are preferred to the serial VTK file formats whenever possible.

Simple Legacy Formats

The legacy VTK file formats consist of five basic parts.

1. The first part is the file version and identifier. This part contains the single line:

# vtk DataFile Version x.x.

This line must be exactly as shown with the exception of the version number

x.x, which will vary with different

releases of VTK. (Note: the current version number is 3.0. Version 1.0 and 2.0 files are compatible with version 3.0

files.)

2. The second part is the header. The header consists of a character string terminated by end-of-line character

.The

header is 256 characters maximum. The header can be used to describe the data and include any other pertinent

information.

3. The next part is the file format. The file format describes the type of file, either ASCII or binary. On this line the sin-

gle word

ASCII or BINARY must appear.

4. The fourth part is the dataset structure. The geometry part describes the geometry and topology of the dataset. This

part begins with a line containing the keyword

DATASET followed by a keyword describing the type of dataset.

Then, depending upon the type of dataset, other keyword/data combinations define the actual data.

5. The final part describes the dataset attributes. This part begins with the keywords

POINT_DATA or CELL_DATA,fol-

lowed by an integer number specifying the number of points or cells, respectively. (It doesn’t matter whether

POINT_DATA or CELL_DATA comes first.) Other keyword/data combinations then define the actual dataset attribute

values (i.e., scalars, vectors, tensors, normals, texture coordinates, or field data).

An overview of the file format is shown in Figure 1. The first three parts are mandatory, but the other two are optional.

Thus you have the flexibility of mixing and matching dataset attributes and geometry, either by operating system file

manipulation or using VTK filters to merge data. Keywords are case insensitive, and may be separated by whitespace.

Before describing the data file formats please note the following.

• dataType is one of the types

bit, unsigned_char, char, unsigned_short, short, unsigned_int, int,

unsigned_long, long, float,ordouble. These keywords are used to describe the form of the data, both for

reading from file, as well as constructing the appropriate internal objects. Not all data types are supported for all

classes.

2 VTK 4.2 File Formats

• All keyword phrases are written in ASCII form whether the file is binary or ASCII. The binary section of the file (if

in binary form) is the data proper; i.e., the numbers that define points coordinates, scalars, cell indices, and so forth.

• Indices are 0-offset. Thus the first point is point id 0.

• If both the data attribute and geometry/topology part are present in the file, then the number of data values defined

in the data attribute part must exactly match the number of points or cells defined in the geometry/topology part.

• Cell types and indices are of type

int.

• Binary data must be placed into the file immediately after the “newline” (

\n) character from the previous ASCII

keyword and parameter sequence.

• The geometry/topology description must occur prior to the data attribute description.

Binary Files. Binary files in VTK are portable across different computer systems as long as you observe two conditions.

First, make sure that the byte ordering of the data is correct, and second, make sure that the length of each data type is con-

sistent.

Most of the time VTK manages the byte ordering of binary files for you. When you write a binary file on one com-

puter and read it in from another computer, the bytes representing the data will be automatically swapped as necessary.

For example, binary files written on a Sun are stored in big endian order, while those on a PC are stored in little endian

order. As a result, files written on a Sun workstation require byte swapping when read on a PC. (See the class

vtkByteSwap for implementation details.) The VTK data files described here are written in big endian form.

Some file formats, however, do not explicitly define a byte ordering form. You will find that data read or written by

external programs, or the classes vtkVolume16Reader, vtkMCubesReader, and vtkMCubesWriter may have a different

byte order depending on the system of origin. In such cases, VTK allows you to specify the byte order by using the meth-

ods

SetDataByteOrderToBigEndian()

SetDataByteOrderToLittleEndian()

Part 4: Geometry/topology. Type is one of:

STRUCTURED_POINTS

STRUCTURED_GRID

UNSTRUCTURED_GRID

POLYDATA

RECTILINEAR_GRID

FIELD

Part 5: Dataset attributes. The number of data

items

n of each type must match the number

of points or cells in the dataset. (If type is

FIELD, point and cell data should be omitted.

Figure 1 Overview of five parts of VTK data file format.

# vtk DataFile Version 2.0

Really cool data

ASCII | BINARY

DATASET

type

...

POINT_DATA

...

CELL_DATA n

...

Part 1: Header

Part 2: Title (256 characters maximum, termi-

nated with newline \n character)

Part 3: Data type, either ASCII or BINARY

(1)

(2)

(3)

(4)

(5)

Simple Legacy Formats 3

Another problem with binary files is that systems may use a different number of bytes to represent an integer or other

native type. For example, some 64-bit systems will represent an integer with 8-bytes, while others represent an integer

with 4-bytes. Currently, the Visualization Toolkit cannot handle transporting binary files across systems with incompatible

data length. In this case, use ASCII file formats instead.

Dataset Format. The Visualization Toolkit supports five different dataset formats: structured points, structured grid, recti-

linear grid, unstructured grid, and polygonal data. Data with implicit topology (structured data such as vtkImageData and

vtkStructuredGrid) are ordered with x increasing fastest, then y,thenz. These formats are as follows.

• Structured Points

The file format supports 1D, 2D, and 3D structured point datasets. The dimensions n

must be greater than or

equal to 1. The data spacing s

must be greater than 0. (Note: in the version 1.0 data file, spacing was referred

to as “aspect ratio”.

ASPECT_RATIO can still be used in version 2.0 data files, but is discouraged.)

DATASET STRUCTURED_POINTS

DIMENSIONS

ORIGIN xyz

SPACING s

• Structured Grid

The file format supports 1D, 2D, and 3D structured grid datasets. The dimensions n

must be greater than or

equal to 1. The point coordinates are defined by the data in the

POINTS section. This consists of x-y-z data values for

each point.

DATASET STRUCTURED_GRID

DIMENSIONS

POINTS n dataType

...

(n-1)x

(n-1)y

(n-1)z

• Rectilinear Grid

A rectilinear grid defines a dataset with regular topology, and semi-regular geometry aligned along the x-y-z coordi-

nate axes. The geometry is defined by three lists of monotonically increasing coordinate values, one list for each of

the x-y-z coordinate axes. The topology is defined by specifying the grid dimensions, which must be greater than or

equal to 1.

DATASET RECTILINEAR_GRID

DIMENSIONS

X_COORDINATES n

dataType

1...

(nx-1)

Y_COORDINATES n

dataType

1...

(ny-1)

Z_COORDINATES n

dataType

1...

(nz-1)

• Polygonal Data

The polygonal dataset consists of arbitrary combinations of surface graphics primitives vertices (and polyvertices),

lines (and polylines), polygons (of various types), and triangle strips. Polygonal data is defined by the

POINTS

VERTICES

, LINES, POLYGONS,orTRIANGLE_STRIPS sections. The POINTS definition is the same as we saw for

structured grid datasets. The

VERTICES, LINES, POLYGONS,orTRIANGLE_STRIPS keywords define the polygonal

dataset topology. Each of these keywords requires two parameters: the number of cells n and the size of the cell list

size. The cell list size is the total number of integer values required to represent the list (i.e., sum of numPoints and

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