1
2
3 """
4 Blender Python related features
5 ===============================
6
7 L{Back to Main Page<API_intro>}
8
9
10 Introduction:
11 =============
12
13 This page describes special features available to BPython scripts:
14
15 - Command line mode is accessible with the '-P' and '-b' Blender options.
16 - Registration allows scripts to become available from some pre-defined menus
17 in Blender, like Import, Export, Wizards and so on.
18 - Script links are Blender Texts (scripts) executed when a particular event
19 (redraws, .blend file loading, saving, frame changed, etc.) occurs. Now
20 there are also "Space Handlers" to draw onto or get events from a given
21 space (only 3D View now) in some window.
22 - Proper documentation data is used by the 'Scripts Help Browser' script to
23 show help information for any registered script. Your own GUI can use
24 this facility with the L{Blender.ShowHelp} function.
25 - Configuration is for data in your script that can be tweaked according to
26 user taste or needs. Like documentation, this is another helper
27 functionality -- you don't need to provide a GUI yourself to edit config
28 data.
29
30
31 Command line usage:
32 ===================
33
34 Specifying scripts:
35 -------------------
36
37 The '-P' option followed either by:
38 - a script filename (full pathname if not in the same folder where you run
39 the command);
40 - the name of a Text in a .blend file (that must also be specified)
41 will open Blender and immediately run the given script.
42
43 Example::
44
45 # open Blender and execute the given script:
46 blender -P script.py
47
48 Passing parameters:
49 -------------------
50
51 To pass parameters to the script you can:
52 - write them to a file before running Blender, then make your script parse that file;
53 - set environment variables and access them with the 'os' module:
54
55 Examples with parameters being passed to the script via command line::
56
57 # execute a command like:
58
59 myvar=value blender -P script.py
60
61 # and in script.py access myvar with os.getenv
62 # (os.environ and os.setenv are also useful):
63
64 # script.py:
65 import os
66 val = os.getenv('myvar')
67
68 # To pass multiple parameters, simply write them in sequence,
69 # separated by spaces:
70
71 myvar1=value1 myvar2=value2 mystr="some string data" blender -P script.py
72
73 Background mode:
74 ----------------
75
76 In '-b' mode no windows will be opened: the program will run as a command
77 line tool able to render stills and animations and execute any working Python
78 script with complete access to loaded .blend's file contents. Once the task
79 is completed, the program will exit.
80
81 Background mode examples::
82
83 # Open Blender in background mode with file 'myfile.blend'
84 # and run the script 'script.py':
85
86 blender -b myfile.blend -P script.py
87
88 # Note: a .blend file is always required. 'script.py' can be a file
89 # in the file system or a Blender Text stored in 'myfile.blend'.
90
91 # Let's assume 'script.py' has code to render the current frame;
92 # this line will set the [s]tart and [e]nd (and so the current) frame to
93 # frame 44 and call the script:
94
95 blender -b myfile.blend -s 44 -e 44 -P script.py
96
97 # Using now a script written to render animations, we set different
98 # start and end frames and then execute this line:
99
100 blender -b myfile.blend -s 1 -e 10 -P script.py
101
102 # Note: we can also set frames and define if we want a single image or
103 # an animation in the script body itself, naturally.
104
105 The rendered pictures will be written to the default render folder, that can
106 also be set via BPython (take a look at L{Render.RenderData}). Their
107 names will be the equivalent frame number followed by the extension of the
108 chosen image type: 0001.png, for example. To rename them to something else,
109 coders can use the C{rename} function in the standard 'os' Python module.
110
111 Reminder: if you just need to render, it's not necessary to have a script.
112 Blender can create stills and animations with its own command line arguments.
113 Example:
114 - a single image at frame 44: blender -b myfile.blend -f 44
115 - an animation from frame 1 to 10: blender -b myfile.blend -s 1 -e 10 -a
116
117
118 Script links:
119 =============
120
121 Object script links:
122 --------------------
123
124 Users can link Blender Text scripts and objects to have the script
125 code executed when specific events occur to the objects. For example, if a
126 Camera has an script link set to "FrameChanged", the script will be executed
127 whenever the current frame is changed. Links can either be manually added by
128 users on the Buttons window -> Scripts tab or created by another script (see,
129 for example, L{Object.addScriptLink<Object.Object.addScriptLink>}).
130
131 These are the types which can be linked to scripts:
132 - Camera Data;
133 - Lamp Data;
134 - Materials;
135 - Objects;
136 - Scenes;
137 - Worlds.
138
139 And these are the available event choices:
140 - Redraw;
141 - FrameChanged;
142 - Render;
143 - OnLoad (*);
144 - OnSave (*).
145
146 (*) only available for scenes
147
148 There are three L{Blender} module variables that script link authors should
149 be aware of:
150 - B{bylink}: True if the script is running as a script link;
151 - B{link}: the object the running script was linked to (None if this is
152 not a script link);
153 - B{event}: the event type, if the running script is being executed as a
154 script link.
155
156 Example::
157 #script link
158 import Blender
159 if Blender.bylink: # we're running as a script link
160 print "Event: %s for %s" % (Blender.event, Blender.link)
161
162 B{Important note about "Render" events}:
163
164 Each "Render" script link is executed twice: before rendering and after, for
165 reverting changes and for possible clean up actions. Before rendering,
166 'Blender.event' will be "Render" and after rendering it will be "PostRender".
167
168 Example::
169 # render script link
170 import Blender
171 event = Blender.event
172 if event == "Render":
173 # prepare for rendering
174 create_my_very_detailed_mesh_data()
175 elif event == "PostRender":
176 # done rendering, clean up
177 delete_my_very_detailed_mesh_data()
178
179 As suggested by the example above, this is especially useful for script links
180 that need to generate data only useful while rendering, or in case they need
181 to switch between two mesh data objects, one meant for realtime display and
182 the other, more detailed, for renders.
183
184 Space Handler script links:
185 ---------------------------
186
187 This is a new kind of script linked to spaces in a given window. Right now
188 only the 3D View has the necessary hooks, but the plan is to add access to
189 other types, too. Just to clarify naming conventions: in Blender, a screen
190 is partitioned in windows (also called areas) and each window can show any
191 space. Spaces are: 3D View, Text Editor, Scripts, Buttons, User Preferences,
192 Oops, etc.
193
194 Space handlers are texts in the Text Editor, like other script links, but they
195 need to have a special header to be recognized -- B{I{the first line in the
196 text file}} must inform:
197 1. that they are space handlers;
198 2. the space they belong to;
199 3. whether they are EVENT or DRAW handlers.
200
201 Example header for a 3D View EVENT handler::
202
203 # SPACEHANDLER.VIEW3D.EVENT
204
205 Example header for a 3D View DRAW handler::
206
207 # SPACEHANDLER.VIEW3D.DRAW
208
209 Available space handlers can be toggled "on" or "off" in the space header's
210 B{View->Space Handler Scripts} submenu, by the user.
211
212 EVENT space handler scripts are called by that space's event handling callback
213 in Blender. The script receives the event B{before} it is further processed
214 by the program. An EVENT handler script should check Blender.event (compare
215 it against L{Draw} events) and either:
216 - process it (the script must set Blender.event to None then);
217 - ignore it.
218
219 Setting C{Blender.event = None} tells Blender not to go on processing itself
220 the event, because it was grabbed by the script.
221
222 Example::
223
224 # SPACEHANDLER.VIEW3D.EVENT
225
226 import Blender
227 from Blender import Draw
228 evt = Blender.event
229 val = Blender.eventValue
230 return_it = False
231
232 if evt == Draw.LEFTMOUSE:
233 print "Swallowing the left mouse button press"
234 elif evt == Draw.AKEY:
235 print "Swallowing an 'a' character"
236 else:
237 print "Let the 3D View itself process this event: %d with value %d" % (evt, val)
238 return_it = True
239
240 # if Blender should not process itself the passed event:
241 if not return_it: Blender.event = None
242
243 DRAW space handlers are called by that space's drawing callback in Blender.
244 The script is called B{after} the space has been drawn.
245
246 Two of the L{Blender} module variables related to script links assume
247 different roles for space handlers:
248 - B{bylink} is the same: True if the script is running as a script link;
249 - B{link}: integer from the L{Blender}.SpaceHandlers constant dictionary,
250 tells what space this handler belongs to and the handler's type
251 (EVENT, DRAW);
252 - B{event}:
253 - EVENT handlers: an input event (check keys and mouse events in
254 L{Draw}) to be processed or ignored;
255 - DRAW handlers: 0 always;
256 - B{eventValue}:
257 - EVENT handlers: the event value, it indicates mouse button or key
258 presses (since we don't pass releases) as 1 and mouse movements
259 (Draw.MOUSE.X and Draw.MOUSE.Y) as the current x or y coordinate,
260 for example;
261 - DRAW handlers: 0 always.
262
263 B{Guidelines (important)}:
264 - EVENT handlers can access and change Blender objects just like any other
265 script, but they should not draw to the screen, B{use a DRAW handler to do
266 that}. Specifically: L{Draw.Image} and the L{BGL} drawing functions
267 should not be used inside an EVENT handler.
268 - DRAW handlers should leave the space in the same state it was before they
269 were executed. OpenGL attributes and the modelview and projection matrices
270 are automatically saved (pushed) before a DRAW handler runs and restored
271 (popped) after it finishes, no need to worry about that. Draw handlers
272 should not grab events;
273 - If script handlers need to pass information to each other (for example an
274 EVENT handler passing info to a DRAW handler), use the L{Registry} module.
275 - in short: use the event handler to deal with events and the draw handler to
276 draw and your script will be following the recommended practices for
277 Blender code.
278
279 Registering scripts:
280 ====================
281
282 To be registered a script needs two things:
283 - to be either in the default scripts directory or in the user defined scripts
284 path (see User Preferences window -> File Paths tab -> Python path);
285 - to have a proper header.
286
287 Try 'blender -d' to know where your default directory for scripts is, it will
288 inform either the directory or the file with that info already parsed, which is
289 in the same directory of the scripts folder.
290
291 The header should be like this one (all double and single apostrophes below
292 are required)::
293 #!BPY
294
295 # \"\"\"
296 # Name: 'Script Name'
297 # Blender: 233
298 # Group: 'Export'
299 # Submenu: 'All' all
300 # Submenu: 'Selected' sel
301 # Submenu: 'Configure (gui)' gui
302 # Tooltip: 'Export to some format.'
303 # \"\"\"
304
305 where:
306 - B{Name} is the string that will appear in the menu;
307 - B{Blender} is the minimum program version required to run the script;
308 - B{Group} defines where the script will be put, see all groups in the
309 Scripts Window's header, menu "Scripts";
310 - B{Submenu} adds optional submenus for further control;
311 - B{Tooltip} is the (short) tooltip string for the menu entry.
312
313 note:
314 - all double and single apostrophes above are required;
315 - you can "comment out" the header above, by starting lines with
316 '#', like we did. This is not required (except for the first line, #!BPY,
317 of course), but this way the header won't conflict with Python tools that
318 you can use to generate documentation for your script code. Just
319 remember to keep this header above any other line with triple
320 double-quotes (\"\"\") in your script.
321
322 Submenu lines are not required, use them if you want to provide extra
323 options. To see which submenu the user chose, check the "__script__"
324 dictionary in your code: __script__['arg'] has the defined keyword (the word
325 after the submenu string name: all, sel or gui in the example above) of the
326 chosen submenu. For example, if the user clicked on submenu 'Selected' above,
327 __script__['arg'] will be "sel".
328
329 If your script requires extra data or configuration files, there is a special
330 folder where they can be saved: see 'datadir' in L{Blender.Get}.
331
332
333 Documenting scripts:
334 ====================
335
336 The "Scripts Help Browser" script in the Help menu can parse special variables
337 from registered scripts and display help information for users. For that,
338 authors only need to add proper information to their scripts, after the
339 registration header.
340
341 The expected variables:
342
343 - __bpydoc__ (or __doc__) (type: string):
344 - The main help text. Write a first short paragraph explaining what the
345 script does, then add the rest of the help text, leaving a blank line
346 between each new paragraph. To force line breaks you can use <br> tags.
347
348 - __author__ (type: string or list of strings):
349 - Author name(s).
350
351 - __version__ (type: string):
352 - Script version. A good recommendation is using a version number followed
353 by the date in the format YYYY/MM/DD: "1.0 2005/12/31".
354
355 - __url__ (type: string or list of strings):
356 - Internet links that are shown as buttons in the help screen. Clicking
357 them opens the user's default browser at the specified location. The
358 expected format for each url entry is e.g.
359 "Author's site, http://www.somewhere.com". The first part, before the
360 comma (','), is used as the button's tooltip. There are two preset
361 options: "blender" and "blenderartists.org", which link to the Python forums at
362 blender.org and blenderartists.org, respectively.
363
364 - __email__ (optional, type: string or list of strings):
365 - Equivalent to __url__, but opens the user's default email client. You
366 can write the email as someone:somewhere*com and the help script will
367 substitute accordingly: someone@somewhere.com. This is only a minor help
368 to hide emails from spammers, since your script may be available at some
369 site. "scripts" is the available preset, with the email address of the
370 mailing list devoted to scripting in Blender, bf-scripts-dev@blender.org.
371 You should only use this one if you are subscribed to the list:
372 http://projects.blender.org/mailman/listinfo/bf-scripts-dev for more
373 information.
374
375 Example::
376 __author__ = 'Mr. Author'
377 __version__ = '1.0 2005/01/01'
378 __url__ = ["Author's site, http://somewhere.com",
379 "Support forum, http://somewhere.com/forum/", "blender", "blenderartists.org"]
380 __email__ = ["Mr. Author, mrauthor:somewhere*com", "scripts"]
381 __bpydoc__ = \"\"\"\\
382 This script does this and that.
383
384 Explaining better, this script helps you create ...
385
386 You can write as many paragraphs as needed.
387
388 Shortcuts:<br>
389 Esc or Q: quit.<br>
390 etc.
391
392 Supported:<br>
393 Meshes, metaballs.
394
395 Known issues:<br>
396 This is just an example, there's no actual script.
397
398 Notes:<br>
399 You can check scripts bundled with Blender to see more examples of how to
400 add documentation to your own works.
401 \"\"\"
402
403 B{Note}: your own GUI or menu code can display documentation by calling the
404 help browser with the L{Blender.ShowHelp} function.
405
406 Configuring scripts:
407 ====================
408
409 The L{Blender.Registry<Registry>} module provides a simplified way to keep
410 scripts configuration options in memory and also saved in config files.
411 And with the "Scripts Config Editor" script in the System menu users can later
412 view and edit the options easily.
413
414 Let's first clarify what we mean by config options: they are simple data
415 (bools, ints, floats, strings) used by programs to conform to user
416 preferences. The buttons in Blender's User Preferences window are a good
417 example.
418
419 For example, a particular exporter might include:
420 - SEPARATE_MATS = False: a bool variable (True / False) to determine if it
421 should write materials to a separate file;
422 - VERSION = 2: an int to define an specific version of the export format;
423 - TEX_DIR = "/path/to/textures": a default texture dir to prepend to all
424 exported texture filenames instead of their actual paths.
425
426 The script needs to provide users a GUI to configure these options -- or else
427 directly editing the source code would be the only way to change them. And to
428 store changes made to the GUI so they can be reloaded any time the script is
429 executed, programmers have to write and load their own config files (ideally at
430 L{Blender.Get}('udatadir') or, if not available, L{Blender.Get}('datadir')).
431
432 This section describes BPython facilities (based on the L{Registry} module and
433 the config editor) that can take care of this in a simplified (and much
434 recommended) way.
435
436 Here's how it works::
437
438 # sample_exporter.py
439 import Blender
440 from Blender import Registry
441
442 # First define all config variables with their default values:
443 SEPARATE_MATERIALS = True
444 VERSION = True
445 TEX_DIR = ''
446 EXPORT_DIR = ''
447
448 # Then define a function to update the Registry:
449 def registry_update():
450 # populate a dict with current config values:
451 d = {
452 'SEPARATE_MATERIALS': SEPARATE_MATERIALS,
453 'VERSION': VERSION,
454 'TEX_DIR': TEX_DIR,
455 'EXPORT_DIR': EXPORT_DIR
456 }
457 # store the key (optional 3rd arg tells if
458 # the data should also be written to a file):
459 Registry.SetKey('sample_exporter', d, True)
460
461 # (A good convention is to use the script name as Registry key)
462
463 # Now we check if our key is available in the Registry or file system:
464 regdict = Registry.GetKey('sample_exporter', True)
465
466 # If this key already exists, update config variables with its values:
467 if regdict:
468 try:
469 SEPARATE_MATERIALS = regdict['SEPARATE_MATERIALS']
470 VERSION = regdict['VERSION']
471 TEX_DIR = regdict['TEX_DIR']
472 EXPORT_DIR = regdict['EXPORT_DIR']
473
474 # if data was corrupted (or a new version of the script changed
475 # (expanded, removed, renamed) the config vars and users may have
476 # the old config file around):
477 except: update_registry() # rewrite it
478
479 else: # if the key doesn't exist yet, use our function to create it:
480 update_registry()
481
482 # ...
483
484 Hint: nicer code than the simplistic example above can be written by keeping
485 config var names in a list of strings and using the exec function.
486
487 B{Note}: if your script's GUI lets users change config vars, call the
488 registry_update() function in the button events callback to save the changes.
489 On the other hand, you don't need to handle configuration
490 in your own gui, it can be left for the 'Scripts Config Editor',
491 which should have access to your script's config key as soon as the
492 above code is executed once (as soon as SetKey is executed).
493
494 B{Note} (limits for config vars): strings longer than 300 characters are
495 clamped and the number of items in dictionaries, sequences and the config key
496 itself is limited to 60.
497
498
499 Scripts Configuration Editor:
500 -----------------------------
501
502 This script should be available from the System menu in the Scripts window.
503 It provides a GUI to view and edit saved configuration data, both from the
504 Registry dictionary in memory and the scripts config data dir. This is
505 useful for all scripts with config vars, but especially for those without GUIs,
506 like most importers and exporters, since this editor will provide one for them.
507
508 The example above already gives a good idea of how the information can be
509 prepared to be accessible from this editor, but there is more worth knowing:
510
511 1. String vars that end with '_dir' or '_file' (can be upper case, too) are
512 recognized as input boxes for dirs or files and a 'browse' button is added to
513 their right side, to call the file selector.
514
515 2. Both key names and configuration variables names starting with an
516 underscore ('_') are ignored by the editor. Programmers can use this feature
517 for any key or config var that is not meant to be configured by this editor.
518
519 3. The following information refers to extra config variables that may be
520 added specifically to aid the configuration editor script. To clarify, in the
521 example code above these variables (the string 'script' and the dictionaries
522 'tooltips' and 'limits') would appear along with SEPARATE_MATERIALS, VERSION,
523 TEX_DIR and EXPORT_DIR, wherever they are written.
524
525 Minor note: these names are case insensitive: tooltips, TOOLTIPS, etc. are all
526 recognized.
527
528 3.1 The config editor will try to display a 'help' button for a key, to show
529 documentation for the script that owns it. To find this "owner script", it
530 will first look for a config variable called 'script', a string containing
531 the name of the owner Python file (with or without '.py' extension)::
532
533 script = 'sample_exporter.py'
534
535 If there is no such variable, the editor will check if the file formed by the
536 key name and the '.py' extension exists. If both alternatives fail, no help
537 button will be displayed.
538
539 3.2 You can define tooltips for the buttons that the editor creates for your
540 config data (string input, toggle, number sliders). Simply create a dict
541 called 'tooltips', where config var names are keys and their tooltips,
542 values::
543
544 tooltips = {
545 'EXPORT_DIR': 'default folder where exported files should be saved',
546 'VERBOSE': 'print info and warning messages to the console',
547 'SEPARATE_MATERIALS': 'write materials to their own file'
548 }
549
550 3.3 Int and float button sliders need min and max limits. This can be passed
551 to the editor via a dict called 'limits' (ivar1, ivar2 and fvar are meant as
552 extra config vars that might have been in the example code above)::
553
554 limits = {'ivar1': [-10, 10], 'ivar2': [0, 100], 'fvar1': [-12.3, 15.4]}
555
556 4. The Config Editor itself maintains a Registry key called "General", with
557 general options relevant to many scripts, like "verbose" to tell if the user
558 wants messages printed to the console and "confirm overwrite", to know if
559 a script should ask for confirmation before overwriting files (all exporters
560 are recommended to access the General key and check this var -- L{sys.exists
561 <Sys.exists>} tells if files or folders already exist).
562
563 Hint: for actual examples, try the ac3d importer and exporter (it's enough to
564 call them from the menus then cancel with ESC), as those have been updated to
565 use this config system. After calling them their config data will be available
566 in the Config Editor. We also recommend adding a section about config vars
567 in your script's help info, as done in the ac3d ones.
568
569 L{Back to Main Page<API_intro>}
570 ===============================
571 """
572