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-<html>
-<head>
- <link rel="stylesheet" type="text/css" href="mystery_of_the_blend.css" media="screen, print">
- <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
- <title>The mystery of the blend</title>
-</head>
-
-<body>
-<div class="title">The mystery of the blend</div>
-<div class="subtitle">The blender file-format explained</div>
-<div class="contact">
-<label>Author</label> Jeroen Bakker<br>
-<label>Email</label> <a href="mailto:j.bakker@atmind.nl">j.bakker@atmind.nl</a><br>
-<label>Website</label> <a href="http://www.atmind.nl/blender/">http://www.atmind.nl/blender</a><br>
-<label>Version</label> 06-10-2010<br>
-</div>
-
-<a name="introduction" href="#introduction" ><h2>Introduction</h2></a>
-</a>
-
-<p>In this article I will describe the
- blend-file-format with a request to tool-makers to support blend-file.
-
-</p>
-<p>First I'll describe how Blender works with blend-files. You'll notice
- why the blend-file-format is not that well documented, as from
-Blender's perspective this is not needed.
-We look at the global file-structure of a blend-file (the file-header
-and file-blocks).
-After this is explained, we go deeper to the core of the blend-file, the
- DNA-structures. They hold the blue-prints of the blend-file and the key
- asset of understanding blend-files.
-When that's done we can use these DNA-structures to read information
-from elsewhere in the blend-file.
-
-</p>
-<p>
-In this article we'll be using the default blend-file from Blender 2.54,
- with the goal to read the output resolution from the Scene.
-The article is written to be programming language independent and I've
-setup a web-site for support.
-</p>
-
-<a name="loading-and-saving-in-blender" href="#loading-and-saving-in-blender">
-<h2>Loading and saving in Blender</h2>
-</a>
-
-<p>
-Loading and saving in Blender is very fast and Blender is known to
-have excellent downward and upward compatibility. Ton Roosendaal
-demonstrated that in December 2008 by loading a 1.0 blend-file using
-Blender 2.48a [ref: <a href="http://www.blendernation.com/2008/12/01/blender-dna-rna-and-backward-compatibility/">http://www.blendernation.com/2008/12/01/blender-dna-rna-and-backward-compatibility/</a>].
-</p>
-
-<p>
-Saving complex scenes in Blender is done within seconds. Blender
-achieves this by saving data in memory to disk without any
-transformations or translations. Blender only adds file-block-headers to
- this data. A file-block-header contains clues on how to interpret the
-data. After the data, all internally Blender structures are stored.
-These structures will act as blue-prints when Blender loads the file.
-Blend-files can be different when stored on different hardware platforms
- or Blender releases. There is no effort taken to make blend-files
-binary the same. Blender creates the blend-files in this manner since
-release 1.0. Backward and upwards compatibility is not implemented when
-saving the file, this is done during loading.
-</p>
-
-<p>
-When Blender loads a blend-file, the DNA-structures are read first.
-Blender creates a catalog of these DNA-structures. Blender uses this
-catalog together with the data in the file, the internal Blender
-structures of the Blender release you're using and a lot of
-transformation and translation logic to implement the backward and
-upward compatibility. In the source code of blender there is actually
-logic which can transform and translate every structure used by a
-Blender release to the one of the release you're using [ref: <a href="http://download.blender.org/source/blender-2.48a.tar.gz">http://download.blender.org/source/blender-2.48a.tar.gz</a>
- <a href="https://svn.blender.org/svnroot/bf-blender/tags/blender-2.48-release/source/blender/blenloader/intern/readfile.c">blender/blenloader/intern/readfile.c</a> lines
-4946-7960]. The more difference between releases the more logic is
-executed.
-</p>
-
-<p>
-The blend-file-format is not well documented, as it does not differ from
- internally used structures and the file can really explain itself.
-</p>
-
-<a name="global-file-structure" href="#global-file-structure">
-<h2>Global file-structure</h2>
-</a>
-
-<p>
-This section explains how the global file-structure can be read.
-</p>
-
-<ul>
-<li>A blend-file always start with the <b>file-header</b></li>
-<li>After the file-header, follows a list of <b>file-blocks</b> (the default blend file of Blender 2.48 contains more than 400 of these file-blocks).</li>
-<li>Each file-block has a <b>file-block header</b> and <b>file-block data</b></li>
-<li>At the end of the blend-file there is a section called "<a href="#structure-DNA" style="font-weight:bold">Structure DNA</a>", which lists all the internal structures of the Blender release the file was created in</li>
-<li>The blend-file ends with a file-block called 'ENDB'</li>
-</ul>
-
-<!-- file scheme -->
-<div class="box-solid" style="width:20%; margin-left:35%; font-size:0.8em;">
-
- <p class="code"><b>File.blend</b></p>
-
- <div class="box"><p class="code">File-header</p></div>
-
- <div class="box-solid"><p class="code">File-block</p>
- <div class="box"><p class="code">Header</p></div>
- <div class="box"><p class="code">Data</p></div>
- </div>
-
- <div class="box" style="border-style:dashed"><p class="code">File-block</p></div>
- <div class="box" style="border-style:dashed"><p class="code">File-block</p></div>
-
- <div class="box-solid"><p class="code">File-block 'Structure DNA'</p>
- <div class="box"><p class="code">Header ('DNA1')</p></div>
- <div class="box-solid">
- <p class="code">Data ('SDNA')</p>
- <div class="box">
- <p class="code">Names ('NAME')</p>
- </div>
- <div class="box">
- <p class="code">Types ('TYPE')</p>
- </div>
- <div class="box">
- <p class="code">Lengths ('TLEN')</p>
- </div>
- <div class="box">
- <p class="code">Structures ('STRC')</p>
- </div>
- </div>
- </div>
-
- <div class="box-solid"><p class="code">File-Block 'ENDB'</p></div>
-
-</div><!-- end of file scheme -->
-
-<a name="file-header" href="#file-header">
-<h3>File-Header</h3>
-</a>
-
-<p>
-The first 12 bytes of every blend-file is the file-header. The
-file-header has information on Blender (version-number) and the PC the
-blend-file was saved on (pointer-size and endianness). This is required
-as all data inside the blend-file is ordered in that way, because no
-translation or transformation is done during saving.
-The next table describes the information in the file-header.
-</p>
-
-<table>
-<caption>File-header</caption>
-<thead>
-<tr><th>reference</th>
- <th>structure</th>
- <th>type</th>
- <th>offset</th>
- <th>size</th></tr>
-</thead>
-<tbody>
-<tr><td>identifier</td>
- <td>char[7]</td>
- <td>File identifier (always 'BLENDER')</td>
- <td>0</td>
- <td>7</td></tr>
-<tr><td>pointer-size</td>
- <td>char</td>
- <td>Size of a pointer; all pointers in the file are stored in this format. '_' means 4 bytes or 32 bit and '-' means 8 bytes or 64 bits.</td>
- <td>7</td>
- <td>1</td></tr>
-<tr><td>endianness</td>
- <td>char</td>
- <td>Type of byte ordering used; 'v' means little endian and 'V' means big endian.</td>
- <td>8</td>
- <td>1</td></tr>
-<tr><td>version-number</td>
- <td>char[3]</td>
- <td>Version of Blender the file was created in; '254' means version 2.54</td>
- <td>9</td>
- <td>3</td></tr>
-</tbody>
-</table>
-
-<p>
-<a href="http://en.wikipedia.org/wiki/Endianness">Endianness</a> addresses the way values are ordered in a sequence of bytes(see the <a href="#example-endianess">example</a> below):
-</p>
-
-<ul>
- <li>in a big endian ordering, the largest part of the value is placed on the first byte and
- the lowest part of the value is placed on the last byte,</li>
- <li>in a little endian ordering, largest part of the value is placed on the last byte
- and the smallest part of the value is placed on the first byte.</li>
-</ul>
-
-<p>
-Nowadays, little-endian is the most commonly used.
-</p>
-
-<a name="example-endianess"></a>
-<div class="box">
-<p onclick="location.href='#example-endianess'" class="box-title">
-Endianess Example
-</p>
-<p>
-Writing the integer <code class="evidence">0x4A3B2C1Dh</code>, will be ordered:
-<ul>
-<li>in big endian as <code class="evidence">0x4Ah</code>, <code class="evidence">0x3Bh</code>, <code class="evidence">0x2Ch</code>, <code class="evidence">0x1Dh</code></li>
-<li>in little endian as <code class="evidence">0x1Dh</code>, <code class="evidence">0x2Ch</code>, <code class="evidence">0x3Bh</code>, <code class="evidence">0x4Ah</code></li>
-</ul>
-</p>
-</div>
-
-<p>
-Blender supports little-endian and big-endian.<br>
-This means that when the endianness
-is different between the blend-file and the PC your using, Blender changes it to the byte ordering
-of your PC.
-</p>
-
-<a name="example-file-header"></a>
-<div class="box">
-<p onclick="location.href='#example-file-header'" class="box-title">
-File-header Example
-</p>
-
-<p>
-This hex-dump describes a file-header created with <code>blender</code> <code>2.54.0</code> on <code>little-endian</code> hardware with a <code>32 bits</code> pointer length.
-<code class="block"> <span class="descr">pointer-size version-number
- | |</span>
-0000 0000: [42 4C 45 4E 44 45 52] [5F] [76] [32 35 34] BLENDER_v254 <span class="descr">
- | |
- identifier endianness</span></code>
-</p>
-</div>
-
-<a name="file-blocks" href="#file-blocks"><h3>File-blocks</h3></a>
-
-<p>
-File-blocks contain a "<a href="#file-block-header">file-block header</a>" and "file-block data".
-</p>
-
-<a name="file-block-header" href="#file-block-header"><h3>File-block headers</h3></a>
-
-<p>
-The file-block-header describes:
-</p>
-
-<ul>
-<li>the type of information stored in the
-file-block</li>
-<li>the total length of the data</li>
-<li>the old memory
-pointer at the moment the data was written to disk</li>
-<li>the number of items of this information</li>
-</ul>
-
-<p>
-As we can see below, depending on the pointer-size stored in the file-header, a file-block-header
-can be 20 or 24 bytes long, hence it is always aligned at 4 bytes.
-</p>
-
-<table>
-<caption>File-block-header</caption>
-<thead>
-<tr>
-<th>reference</th>
- <th>structure</th>
- <th>type</th>
- <th>offset</th>
- <th>size</th></tr></thead>
-<tbody>
-<tr><td>code</td>
- <td>char[4]</td>
- <td>File-block identifier</td>
- <td>0</td>
- <td>4</td></tr>
-<tr><td>size</td>
- <td>integer</td>
- <td>Total length of the data after the file-block-header</td>
- <td>4</td>
- <td>4</td></tr>
-<tr><td>old memory address</td>
- <td>void*</td>
- <td>Memory address the structure was located when written to disk</td>
- <td>8</td>
- <td>pointer-size (4/8)</td></tr>
-<tr><td>SDNA index</td>
- <td>integer</td>
- <td>Index of the SDNA structure</td>
- <td>8+pointer-size</td>
- <td>4</td></tr>
-<tr><td>count</td>
- <td>integer</td>
- <td>Number of structure located in this file-block</td>
- <td>12+pointer-size</td>
- <td>4</td></tr>
-</tbody>
-</table>
-
-<p>
-The above table describes how a file-block-header is structured:
-</p>
-
-<ul>
-<li><code>Code</code> describes different types of file-blocks. The code determines with what logic the data must be read. <br>
-These codes also allows fast finding of data like Library, Scenes, Object or Materials as they all have a specific code. </li>
-<li><code>Size</code> contains the total length of data after the file-block-header.
-After the data a new file-block starts. The last file-block in the file
-has code 'ENDB'.</li>
-<li><code>Old memory address</code> contains the memory address when the structure
-was last stored. When loading the file the structures can be placed on
-different memory addresses. Blender updates pointers to these structures
- to the new memory addresses.</li>
-<li><code>SDNA index</code> contains the index in the DNA structures to be used when
-reading this file-block-data. <br>
-More information about this subject will be explained in the <a href="#reading-scene-information">Reading scene information section</a>.</li>
-<li><code>Count</code> tells how many elements of the specific SDNA structure can be found in the data.</li>
-</ul>
-
-<a name="example-file-block-header"></a>
-<div class="box">
-<p onclick="location.href='#example-file-block-header'" class="box-title">
-Example
-</p>
-<p>
-This hex-dump describes a File-block (= <span class="header">File-block header</span> + <span class="data">File-block data</span>) created with <code>blender</code> <code>2.54</code> on <code>little-endian</code> hardware with a <code>32 bits</code> pointer length.<br>
-<code class="block"><span class="descr"> file-block
- identifier='SC' data size=1404 old pointer SDNA index=150
- | | | |</span>
-0000 4420: <span class="header">[53 43 00 00] [7C 05 00 00] [68 34 FB 0B] [96 00 00 00]</span> SC.. `... ./.. ....
-0000 4430: <span class="header">[01 00 00 00]</span> <span class="data">[xx xx xx xx xx xx xx xx xx xx xx xx</span> .... xxxx xxxx xxxx<span class="descr">
- | |
- count=1 file-block data (next 1404 bytes)</span>
-</code>
-</p>
-
-<ul>
-<li>The code <code>'SC'+0x00h</code> identifies that it is a Scene. </li>
-<li>Size of the data is 1404 bytes (0x0000057Ch = 0x7Ch + 0x05h * 256 = 124 + 1280)</li>
-<li>The old pointer is 0x0BFB3468h</li>
-<li>The SDNA index is 150 (0x00000096h = 6 + 9 * 16 = 6 + 144)</li>
-<li>The section contains a single scene (count = 1).</li>
-</ul>
-
-<p>
-Before we can interpret the data of this file-block we first have to read the DNA structures in the file.
-The section "<a href="#structure-DNA">Structure DNA</a>" will show how to do that.
-</p>
-</div>
-
-<a name="structure-DNA" href="#structure-DNA"><h2>Structure DNA</h2></a>
-
-<a name="DNA1-file-block" href="#DNA1-file-block"><h3>The DNA1 file-block</h3></a>
-
-<p>
-Structure DNA is stored in a file-block with code 'DNA1'. It can be just before the 'ENDB' file-block.
-</p>
-
-<p>
-The 'DNA1' file-block contains all internal structures of the Blender release the
-file was created in. <br>
-These structure can be described as C-structures: they can hold fields, arrays and
-pointers to other structures, just like a normal C-structure.
-
-<p>
-<code class="block">struct SceneRenderLayer {
- struct SceneRenderLayer *next, *prev;
- char name[32];
- struct Material *mat_override;
- struct Group *light_override;
- unsigned int lay;
- unsigned int lay_zmask;
- int layflag;
- int pad;
- int passflag;
- int pass_xor;
-};
-</code>
-</p>
-
-<p>
-For example,a blend-file created with Blender 2.54 the 'DNA1' file-block is 57796 bytes long and contains 398 structures.
-</p>
-
-<a name="DNA1-file-block-header" href="#DNA1-file-block-header"><h3>DNA1 file-block-header</h3></a>
-
-<p>
-The DNA1 file-block header follows the same rules of any other file-block, see the example below.
-</p>
-
-<a name="example-DNA1-file-block-header"></a>
-<div class="box">
-<p onclick="location.href='#example-DNA1-file-block-header'" class="box-title">
-Example
-</p>
-<p>
-This hex-dump describes the file-block 'DNA1' header created with <code>blender</code> <code>2.54.0</code> on <code>little-endian</code> hardware with a <code>32 bits</code> pointer length.<br>
-<code class="block"><span class="descr"> (file-block
- identifier='DNA1') data size=57796 old pointer SDNA index=0
- | | | |</span>
-0004 B060 <span class="header">[44 4E 41 31] [C4 E1 00 00] [C8 00 84 0B] [00 00 00 00]</span> DNA1............
-0004 B070 <span class="header">[01 00 00 00]</span> <span class="fade">[53 44 4E 41 4E 41 4D 45 CB 0B 00 00</span> ....<span class="fade">SDNANAME....</span><span class="descr">
- | |
- count=1 'DNA1' file-block data (next 57796 bytes)</span>
-</code>
-</p>
-</div>
-
-<a name="DNA1-file-block-data" href="#DNA1-file-block-data"><h3>DNA1 file-block data</h3></a>
-<p>
-The next section describes how this information is ordered in the <b>data</b> of the 'DNA1' file-block.
-</p>
-
-<table>
-<caption>Structure of the DNA file-block-data</caption>
-<thead>
- <tr><th colspan="2">repeat condition</th>
- <th>name</th>
- <th>type</th>
- <th>length</th>
- <th>description</th></tr>
-</thead>
-<tbody>
-<tr><td></td>
- <td></td>
- <td>identifier</td>
- <td>char[4]</td>
- <td>4</td>
- <td>'SDNA'</td></tr>
-<tr><td></td>
- <td></td>
- <td>name identifier</td>
- <td>char[4]</td>
- <td>4</td>
- <td>'NAME'</td></tr>
-<tr><td></td>
- <td></td>
- <td>#names</td>
- <td>integer</td>
- <td>4</td>
- <td>Number of names follows</td></tr>
-<tr><td>for(#names)</td>
- <td></td>
- <td>name</td>
- <td>char[]</td>
- <td>?</td>
- <td>Zero terminating string of name, also contains pointer and simple array definitions (e.g. '*vertex[3]\0')</td></tr>
-<tr><td></td>
- <td></td>
- <td>type identifier</td>
- <td>char[4]</td>
- <td>4</td>
- <td>'TYPE' this field is aligned at 4 bytes</td></tr>
-<tr><td></td>
- <td></td>
- <td>#types</td>
- <td>integer</td>
- <td>4</td>
- <td>Number of types follows</td></tr>
-<tr><td>for(#types)</td>
- <td></td>
- <td>type</td>
- <td>char[]</td>
- <td>?</td>
- <td>Zero terminating string of type (e.g. 'int\0')</td></tr>
-<tr><td></td>
- <td></td>
- <td>length identifier</td>
- <td>char[4]</td>
- <td>4</td>
- <td>'TLEN' this field is aligned at 4 bytes</td></tr>
-<tr><td>for(#types)</td>
- <td></td>
- <td>length</td>
- <td>short</td>
- <td>2</td>
- <td>Length in bytes of type (e.g. 4)</td></tr>
-<tr><td></td>
- <td></td>
- <td>structure identifier</td>
- <td>char[4]</td>
- <td>4</td>
- <td>'STRC' this field is aligned at 4 bytes</td></tr>
-<tr><td></td>
- <td></td>
- <td>#structures</td>
- <td>integer</td>
- <td>4</td>
- <td>Number of structures follows</td></tr>
-<tr><td>for(#structures)</td>
- <td></td>
- <td>structure type</td>
- <td>short</td>
- <td>2</td>
- <td>Index in types containing the name of the structure</td></tr>
-<tr><td>..</td>
- <td></td>
- <td>#fields</td>
- <td>short</td>
- <td>2</td>
- <td>Number of fields in this structure</td></tr>
-<tr><td>..</td>
- <td>for(#field)</td>
- <td>field type</td>
- <td>short</td>
- <td>2</td>
- <td>Index in type</td></tr>
-<tr><td>for end</td>
- <td>for end</td>
- <td>field name</td>
- <td>short</td>
- <td>2</td>
- <td>Index in name</td></tr>
-</tbody>
-</table>
-
-<p>
-As you can see, the structures are stored in 4 arrays: names, types,
-lengths and structures. Every structure also contains an array of
-fields. A field is the combination of a type and a name. From this
-information a catalog of all structures can be constructed.
-The names are stored as how a C-developer defines them. This means that
-the name also defines pointers and arrays.
-(When a name starts with '*' it is used as a pointer. when the name
-contains for example '[3]' it is used as a array of 3 long.)
-In the types you'll find simple-types (like: 'integer', 'char',
-'float'), but also complex-types like 'Scene' and 'MetaBall'.
-'TLEN' part describes the length of the types. A 'char' is 1 byte, an
-'integer' is 4 bytes and a 'Scene' is 1376 bytes long.
-</p>
-
-<div class="box">
-<p class="box-title">
-Note
-</p>
-<p>
-All identifiers, are arrays of 4 chars, hence they are all aligned at 4 bytes.
-</p>
-</div>
-
-<a name="example-DNA1-file-block-data"></a>
-<div class="box">
-<p onclick="location.href='#example-DNA1-file-block-data'" class="box-title">
-Example
-</p>
-<p>
-Created with <code>blender</code> <code>2.54.0</code> on <code>little-endian</code> hardware with a <code>32 bits</code> pointer length.
-</p>
-
-<a name="DNA1-data-array-names" href="#DNA1-data-array-names"><h4>The names array</h4></a>
-<p>
-The first names are: *next, *prev, *data, *first, *last, x, y, xmin, xmax, ymin, ymax, *pointer, group, val, val2, type, subtype, flag, name[32], ...
-<code class="block"><span class="descr"> file-block-data identifier='SDNA' array-id='NAME' number of names=3019
- | | |</span>
-0004 B070 <span class="fade">01 00 00 00 [53 44 4E 41]</span><span class="data">[4E 41 4D 45] [CB 0B 00 00]</span> <span class="fade">....SDNA</span>NAME....
-0004 B080 <span class="data">[2A 6E 65 78 74 00][2A 70 72 65 76 00] [2A 64 61 74</span> *next.*prev.*dat<span class="descr">
- | | |
- '*next\0' '*prev\0' '*dat'</span><span class="fade">
- ....
- .... (3019 names)</span>
-</code>
-</p>
-
-<div class="box">
-<p class="box-title">
-Note
-</p>
-<p>
-While reading the DNA you'll will come across some strange
-names like '(*doit)()'. These are method pointers and Blender updates
-them to the correct methods.
-</p>
-</div>
-
-<a name="DNA1-data-array-types" href="#DNA1-data-array-types"><h4>The types array</h4></a>
-<p>
-The first types are: char, uchar, short, ushort, int, long, ulong, float, double, void, Link, LinkData, ListBase, vec2s, vec2f, ...
-<code class="block"><span class="descr"> array-id='TYPE'
- |</span>
-0005 2440 <span class="fade">6F 6C 64 5B 34 5D 5B 34 5D 00 00 00</span> [54 59 50 45] <span class="fade">old[4][4]...</span>TYPE
-0005 2450 [C9 01 00 00] [63 68 61 72 00] [75 63 68 61 72 00][73 ....char.uchar.s<span class="descr">
- | | | |
- number of types=457 'char\0' 'uchar\0' 's'</span><span class="fade">
- ....
- .... (457 types)</span>
-</code>
-</p>
-
-<a name="DNA1-data-array-lengths" href="#DNA1-data-array-lengths"><h4>The lengths array</h4></a>
-<p>
-<code class="block"><span class="descr"> char uchar ushort short
- array-id length length length length
- 'TLEN' 1 1 2 2</span>
-0005 3AA0 <span class="fade">45 00 00 00</span> [54 4C 45 4E] [01 00] [01 00] [02 00] [02 00] <span class="fade">E...</span>TLEN........
- <span class="fade">....</span>
-0005 3AC0 [08 00] [04 00] [08 00] [10 00] [10 00] [14 00] [4C 00] [34 00] ............L.4.<span class="descr">
- 8 4 8
- ListBase vec2s vec2f ... etc
- length len length </span><span class="fade">
- ....
- .... (457 lengths, same as number of types)</span>
-</code>
-</p>
-
-<a name="DNA1-data-array-structures" href="#DNA1-data-array-structures"><h4>The structures array</h4></a>
-<p>
-<code class="block"><span class="descr"> array-id='STRC'
- |</span>
-0005 3E30 <span class="fade">40 00 38 00 60 00 00 00 00 00 00 00</span> [53 54 52 43] <span class="fade">@.8.`.......</span>STRC
-0005 3E40 [8E 01 00 00] [0A 00] [02 00] [0A 00] [00 00] [0A 00] [01 00] ................<span class="descr">
- 398 10 2 10 0 10 0
- number of index fields index index index index
- structures in <a href="#DNA1-data-array-types">types</a> in <a href="#DNA1-data-array-types">types</a> in <a href="#DNA1-data-array-names">names</a> in <a href="#DNA1-data-array-types">types</a> in <a href="#DNA1-data-array-names">names</a></span><span class="fade">
- ' '----------------' '-----------------' '
- ' field 0 field 1 '
- '--------------------------------------------------------'
- structure 0
- ....
- .... (398 structures, each one describeing own type, and type/name for each field)</span>
-</code>
-</p>
-</div>
-
-<p>
-The DNA structures inside a Blender 2.48 blend-file can be found at <a href="http://www.atmind.nl/blender/blender-sdna.html">http://www.atmind.nl/blender/blender-sdna.html</a>.
-
-If we understand the DNA part of the file it is now possible to read
-information from other parts file-blocks. The next section will tell us
-how.
-</p>
-
-<a name="reading-scene-information" href="#reading-scene-information"><h2>Reading scene information</h2></a>
-
-<p>
-Let us look at <a href="#example-file-block-header">the file-block header we have seen earlier</a>:<br>
-</p>
-<ul>
-<li>the file-block identifier is <code>'SC'+0x00h</code></li>
-<li>the SDNA index is 150</li>
-<li>the file-block size is 1404 bytes</li>
-</ul>
-<p>
-Now note that:
-<ul>
-<li>the structure at index 150 in the DNA is a structure of type 'Scene' (counting from 0).</li>
-<li>the associated type ('Scene') in the DNA has the length of 1404 bytes.</li>
-</ul>
-</p>
-
-<p>
-We can map the Scene structure on the data of the file-blocks.
-But before we can do that, we have to flatten the Scene-structure.
-
-<code class="block">struct Scene {
- ID id; <span class="descr">// 52 bytes long (ID is different a structure)</span>
- AnimData *adt; <span class="descr">// 4 bytes long (pointer to an AnimData structure)</span>
- Object *camera; <span class="descr">// 4 bytes long (pointer to an Object structure)</span>
- World *world; <span class="descr">// 4 bytes long (pointer to an Object structure)</span>
- ...
- float cursor[3]; <span class="descr">// 12 bytes long (array of 3 floats)</span>
- ...
-};
-</code>
-
-The first field in the Scene-structure is of type 'ID' with the name 'id'.
-Inside the list of DNA structures there is a structure defined for type 'ID' (structure index 17).
-
-<code class="block">struct ID {
- void *next, *prev;
- struct ID *newid;
- struct Library *lib;
- char name[24];
- short us;
- short flag;
- int icon_id;
- IDProperty *properties;
-};
-</code>
-
-The first field in this structure has type 'void' and name '*next'. <br>
-Looking in the structure list there is no structure defined for type 'void': it is a simple type and therefore the data should be read.
-The name '*next' describes a pointer.
-As we see, the first 4 bytes of the data can be mapped to 'id.next'.
-</p>
-
-<p>
-Using this method we'll map a structure to its data. If we want to
-read a specific field we know at which offset in the data it is located
-and how much space it takes.<br>
-The next table shows the output of this flattening process for some
-parts of the Scene-structure. Not all rows are described in the table as
- there is a lot of information in a Scene-structure.
-</p>
-
-<table>
-<caption>Flattened SDNA structure 150: Scene</caption>
-<thead>
-<tr><th>reference</th>
- <th>structure</th>
- <th>type</th><th>name</th>
- <th>offset</th><th>size</th>
- <th>description</th></tr>
-</thead>
-<tbody>
-<tr><td>id.next</td><td><a href="#struct:ID">ID</a></td>
- <td>void</td><td>*next</td>
- <td>0</td>
- <td>4</td>
- <td>Refers to the next scene</td></tr>
-<tr><td>id.prev</td><td><a href="#struct:ID">ID</a></td>
- <td>void</td><td>*prev</td>
- <td>4</td>
- <td>4</td>
- <td>Refers to the previous scene</td></tr>
-<tr><td>id.newid</td><td><a href="#struct:ID">ID</a></td>
- <td>ID</td><td>*newid</td>
- <td>8</td>
- <td>4</td>
- <td></td></tr>
-<tr><td>id.lib</td><td><a href="#struct:ID">ID</a></td>
- <td>Library</td><td>*lib</td>
- <td>12</td>
- <td>4</td>
- <td></td></tr>
-<tr><td>id.name</td><td><a href="#struct:ID">ID</a></td>
- <td>char</td><td>name[24]</td>
- <td>16</td>
- <td>24</td>
- <td>'SC'+the name of the scene as displayed in Blender</td></tr>
-<tr><td>id.us</td><td><a href="#struct:ID">ID</a></td>
- <td>short</td><td>us</td>
- <td>40</td>
- <td>2</td>
- <td></td></tr>
-<tr><td>id.flag</td><td><a href="#struct:ID">ID</a></td>
- <td>short</td><td>flag</td><td>42</td><td>2</td>
- <td></td></tr>
-<tr><td>id.icon_id</td><td><a href="#struct:ID">ID</a></td>
- <td>int</td><td>icon_id</td><td>44</td>
- <td>4</td>
- <td></td></tr>
-<tr><td>id.properties</td><td><a href="#struct:ID">ID</a></td>
- <td>IDProperty</td><td>*properties</td>
- <td>48</td>
- <td>4</td>
- <td></td></tr>
-<tr><td>adt</td><td>Scene</td><td>AnimData</td>
- <td>*adt</td>
- <td>52</td>
- <td>4</td>
- <td></td></tr>
-<tr><td>camera</td><td>Scene</td>
- <td>Object</td>
- <td>*camera</td>
- <td>56</td>
- <td>4</td>
- <td>Pointer to the current camera</td></tr>
-<tr><td>world</td><td>Scene</td>
- <td>World</td>
- <td>*world</td>
- <td>60</td>
- <td>4</td>
- <td>Pointer to the current world</td></tr>
-
-<tr><td class="skip" colspan="7">Skipped rows</td></tr>
-
-<tr><td>r.xsch</td><td><a href="#struct:RenderData">RenderData</a>
- </td><td>short</td><td>xsch</td><td>382</td><td>2</td>
- <td>X-resolution of the output when rendered at 100%</td></tr>
-<tr><td>r.ysch</td><td><a href="#struct:RenderData">RenderData</a>
- </td><td>short</td><td>ysch</td><td>384</td><td>2</td>
- <td>Y-resolution of the output when rendered at 100%</td></tr>
-<tr><td>r.xparts</td><td><a href="#struct:RenderData">RenderData</a>
- </td><td>short</td><td>xparts</td><td>386</td><td>2</td>
- <td>Number of x-part used by the renderer</td></tr>
-<tr><td>r.yparts</td><td><a href="#struct:RenderData">RenderData</a>
- </td><td>short</td><td>yparts</td><td>388</td><td>2</td>
- <td>Number of x-part used by the renderer</td></tr>
-
-<tr><td class="skip" colspan="7">Skipped rows</td></tr>
-
-<tr><td>gpd</td><td>Scene</td><td>bGPdata</td><td>*gpd</td><td>1376</td><td>4</td>
- <td></td></tr>
-<tr><td>physics_settings.gravity</td><td><a href="#struct:PhysicsSettings">PhysicsSettings</a>
- </td><td>float</td><td>gravity[3]</td><td>1380</td><td>12</td>
- <td></td></tr>
-<tr><td>physics_settings.flag</td><td><a href="#struct:PhysicsSettings">PhysicsSettings</a>
- </td><td>int</td><td>flag</td><td>1392</td><td>4</td>
- <td></td></tr>
-<tr><td>physics_settings.quick_cache_step</td><td><a href="#struct:PhysicsSettings">PhysicsSettings</a>
- </td><td>int</td><td>quick_cache_step</td><td>1396</td><td>4</td>
- <td></td></tr>
-<tr><td>physics_settings.rt</td><td><a href="#struct:PhysicsSettings">PhysicsSettings</a>
- </td><td>int</td><td>rt</td><td>1400</td><td>4</td>
- <td></td></tr>
-</tbody>
-</table>
-
-<p>
-We can now read the X and Y resolution of the Scene:
-<ul>
-<li>the X-resolution is located on offset 382 of the file-block-data and must be read as a
-short.</li>
-<li>the Y-resolution is located on offset 384 and is also a short</li>
-</ul>
-</p>
-
-<div class="box">
-<p class="box-title">
-Note
-</p>
-<p>
-An array of chars can mean 2 things. The field contains readable
-text or it contains an array of flags (not humanly readable).
-</p>
-</div>
-
-<div class="box">
-<p class="box-title">
-Note
-</p>
-<p>
-A file-block containing a list refers to the DNA structure and has a count larger
-than 1. For example Vertexes and Faces are stored in this way.
-</p>
-</div>
-
-</body>
-</html>
-
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-22 08:14:05 +0300