1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
|
<html>
<head>
<style type="text/css">
.fragment {
font-family: monospace
}
PRE.fragment {
border: 1px solid #CCCCCC;
background-color: #f5f5f5;
margin-top: 4px;
margin-bottom: 4px;
margin-left: 2px;
margin-right: 8px;
padding-left: 6px;
padding-right: 6px;
padding-top: 4px;
padding-bottom: 4px;
}
</style>
</head>
<body>
<h1>Scenery description in XML</h1>
<h2>0 About this document</h2>
<p>
This document describes version 3 of the CRRCsim scenery file format.
</p>
<p>
<b>Disclaimer:</b> This document is not complete yet. It may be inaccurate
or wrong, too.
</p>
<p>
This document does not provide complete examples. Please take a look at
the scenery files you got when downloading/installing CRRCsim. The file
<tt>simple.xml</tt> in CRRCsim's <tt>scenery</tt> folder demonstrates
many of the features discussed in this document.
</p>
<p>
You need to know basics about xml files: they are structured text. Whitespace
and line breaks do not matter in most places. Just take a look at the
examples and you will understand.
</p>
<p>
The files can be edited using a text editor. There are lots of them. Use
something like Notepad++, vi, emacs, joe... Even the standard Windows notepad
will do, but it is recommended to use an editor that features syntax
highlighting for XML files to spot any obvious formatting errors immediately.
</p>
<h3>0.1 Changes</h3>
<table border="1">
<tr><td>2010-01-01</td><td>J. Reucker</td>
<td>
First version of this document.
</td>
</tr>
<tr><td>2010-01-09</td><td>J. Reucker</td>
<td>
Added details about rotation axes in model based scenery.
</td>
</tr>
<tr><td>2010-05-16</td><td>J. Reucker</td>
<td>
Changed sky definition schema: Now multiple sky sections are allowed
in a single XML file.
</td>
</tr>
<tr><td>2012-01-25</td><td>J. Liénard</td>
<td>
Added preview sections
</td>
</tr>
<tr><td>2015-12-30</td><td>L. Gasparini</td>
<td>
Added details about new object attributes
</td>
</tr>
<tr><td>2016-01-20</td><td>L. Gasparini</td>
<td>
Added details about new object population feature and translucent rendering attribute
</td>
</tr>
<tr><td>2016-03-28</td><td>L. Gasparini</td>
<td>
Added details about new object attribute "shadow"
</td>
</tr>
</table>
<h2>1 General information</h2>
<p>Like most other XML files used in CRRCsim, a scenery description starts with
the XML file header and a changelog.
Whenever you edit such a file, please add a new <tt>change</tt> section and fill
in what is needed. The example below shows a template.</p>
<div class="fragment"><pre class="fragment">
<?xml version="1.0"?>
<crrcsimSceneryFile version="4">
<!-- Some general information -->
<name>My scenery</name>
<categories>
<category>Field</category>
</categories>
<description>
<en>My first scenery file for CRRCsim.</en>
</description>
<changelog>
<change>
<date>2009-12-20</date>
<author>Jan Reucker (slowhand_47@gmx.de)</author>
<en>Created.</en>
</change>
</changelog>
</pre></div>
<p>Every text is written in english, so it is enclosed in <tt><en> </en></tt>.
If you want to add something in italian for example, you should enclose it in
<tt><it> </it></tt>. <i>Other languages than <tt>en</tt> are not
supported yet by CRRCsim, so at the time of writing information in other languages
is solely visible for those reading or editing your scenery file directly.</i></p>
<h2>2 Units</h2>
<p>
All numeric attribute values in a scenery file are written as plain numbers
without engineering units. All length or position values are assumed to
be in feet (ft).
</p>
<h2>3 Coordinate system</h2>
<p>
All positional values are specified using the following attributes:
<table border ="1">
<tr><th>Attribute</th>
<th>Axis (internal)</th>
<th>Direction</th></tr>
<tr><td>north</td><td>x</td><td>positive north, negative south</td></tr>
<tr><td>east</td><td>y</td><td>positive east, negative west</td></tr>
<tr><td>height</td><td>-z</td><td>positive up, negative down</td></tr>
</table>
</p>
<p>The attributes listed in the table above are used in all tags
specifying some kind of position. In earlier versions of CRRCsim, the
attributes <tt>x</tt>, <tt>y</tt> and <tt>z</tt> were used. This is
still possible for specifying object positions in a model-based
scenery (for compatibility reasons), but it's strongly discouraged and
may be removed in future versions of CRRCsim without further notice.</p>
<h2>4 Player positions: section <tt>views</tt></h2>
<p>This section defines possible viewpoints for the player. <i>Currently
CRRCsim will only use the first <tt>position</tt> that is found in the <tt>views</tt>
section.</i></p>
<div class="fragment"><pre class="fragment">
<views>
<position name="default" north="0" east="0" height="4" />
</views>
</pre></div>
<h2>5 Starting positions: section <tt>start</tt></h2>
<p>The starting position for the model. As with
the player position, you may specify more than one starting location. The
topmost position will be used as default, but you may select a different one from
the "Launch" dialog: selecting "Launch from start" instead of the default
"Launch from player" shows a drop list of the available start position.</p>
<div class="fragment"><pre class="fragment">
<start>
<position name="field" north="0" east="0" height="4" />
</start>
</pre></div>
<h2>6 Default values: section <tt>default</tt></h2>
<p>Some default values. Right now, you may only specify the default wind
parameters.</p>
<div class="fragment"><pre class="fragment">
<default>
<wind velocity="3" direction="180" />
</default>
</pre></div>
<h2>7 Appearance of the sky: section <tt>sky</tt></h2>
<p>
The appearance of the sky is determined by the <tt><sky></tt> tag.
There are two different types of sky available: a sky dome and a sky box.
A scenery file can contain an arbitrary number of sky definitions. This
allows for simulating different weather conditions or time of day, or
providing different texture resolutions to adapt textured skies to the
available GPU power.
</p>
<h3>7.1 General description</h3>
<p>
The sky section should contain a brief description, which is in turn
composed of a long and a short description. The short description is used
in menus or list boxes, while the long description may contain some more
information.
</p>
<div class="fragment"><pre class="fragment">
<descr_short>
<en>default</en>
</descr_short>
<descr_long>
<en>The default sky box with 512x512 pixel textures.</en>
</descr_long>
</pre></div>
<h3>7.2 Sky dome</h3>
<p>
The sky dome produces a sky like in the first CRRCsim version.
Think of it as a textured semi-sphere above your head. You can set the
texture and the radius of the semi-sphere.
</p>
<div class="fragment"><pre class="fragment">
<sky type="original" texture="textures/clouds.rgb" radius="10000">
<descr_short>
<en>original</en>
</descr_short>
<descr_long>
<en>The original CRRCsim textured sky dome.</en>
</descr_long>
</sky>
</pre></div>
<p>If you omit the texture name, CRRCsim will generate an untextured but
colored (from grey haze on the horizon to deep blue in the zenith)
semi-sphere. This may help those people with broken OpenGL implementations
that don't get the textured dome right.</p>
<div class="fragment"><pre class="fragment">
<sky type="original" />
</pre></div>
<h3>7.3 Sky box</h3>
<p>After CRRCsim version 0.9.6, a new sky rendering method was implemented:
The sky box. It's nothing but a cube with the viewer/player in the middle.
A texture can be projected onto each cube face. If the textures are
seamless and feature the right kind of distortion for the cubical
projection, this will give a very realistic impression of the sky.</p>
<div class="fragment"><pre class="fragment">
<sky type="box" size="10.0">
<descr_short>
<en>default</en>
</descr_short>
<descr_long>
<en>The default sky box with 512x512 pixel textures.</en>
</descr_long>
<textures>
<north filename="textures/skybox_n.rgb" />
<south filename="textures/skybox_s.rgb" />
<west filename="textures/skybox_w.rgb" />
<east filename="textures/skybox_e.rgb" />
<up filename="textures/skybox_u.rgb" />
<down filename="" />
</textures>
</sky>
</pre></div>
<p>Cube faces without a texture will not be rendered.</p>
<p>There are several tools available that deal with artificial landscape/sky
generation. Most of them should be able to generate a set of textures for the
sky box. TerraGen, for example, works like a charm. Just generate a flat
terrain (remember, we're interested in the sky, not the terrain!) and set up
the sky. Set up the camera with a 90 degrees field of vision (FOV) in the
center of the terrain at zero altitude, zero pitch, heading north. Render
a 512x512 pixel image (or any other power-of-two square format, like 256x256
or 1024x1024, if your graphics card can handle it). This is the "north"
texture. Now only change the camera heading to 90 deg. and render the
"east" texture, while 180 deg. and 270 deg. are the setups for
"south" and "west". Then point the camera back north and
pitch it up 90 degrees to render the "up" texture. If you also want
to add a "down" texture, pitch the camera down to -90 degrees while
looking north and render. Remember to save all textures after rendering! The
textures will be saved as ".bmp" (Windows bitmap) files, please
convert them to SGI format (".rgb", turning on RLE compression is
strongly recommended). Then fill in the texture names in the XML file, copy
the textures to the "textures" subdirectory and enjoy your new sky.
</p>
<h2>8 Preview</h2>
<p> A preview image is a small image of the scenery. It is used in the dialogue of scenery selection <tt>(Options / Location)</tt>.
This image has to have, preferably, a dimension of 256x128 pixels and be in a file format accepted by Plib for textures. The format <tt> .jpg </tt> is accepted.<p>
<p>The file used as preview is indicated by the tag <tt><preview></tt> </p>
<div class="fragment"><pre class="fragment">
<preview filename="textures/simple_preview.jpg" />
</pre></div>
<h3>Only one preview by scene</h3>
<p>The definition is placed at the same level as the other sections</p>
<h3>Several previews </h3>
<p>If the scenery contains some variant of sky, it is possible to indicate a specific preview has each. It is necessary for it to put the definition in the accordant sky section.</p>
<div class="fragment"><pre class="fragment">
<sky type="box" size="10.0">
<preview filename="textures/simple_thunderstorm_preview.jpg" />
<descr_short>
<en>Sky of thunderstorm</en>
</descr_short>
<textures>
<north filename="textures/skybox_th_n.rgb" />
<south filename="textures/skybox_th_s.rgb" />
<west filename="textures/skybox_th_w.rgb" />
<east filename="textures/skybox_th_e.rgb" />
<up filename="textures/skybox_th_u.rgb" />
<down filename="" />
</textures>
</sky>
</pre></div>
<p> It is possible to mix both syntaxes: if a varying of sky has no preview, the generic preview is used.</p>
<h2>9 The scene description: section <tt>scene</tt></h2>
<p>The last tag in the current files tells CRRCsim what to render in addition
to the sky. This description starts with the <tt>scene</tt> tag. The
<tt>type</tt> attribute of this tag defines the semantics of the tags inside
the <tt>scene</tt> section.</p>
<p> The optional <tt>altitude</tt> attribute of this tag defines the altitude (in feets) of scenery. It is useful in scenery of mountain to take into account the variation of air density. The height parameters in the scenery description are values relative to this altitude.<p>
<h3>Built-in sceneries: <tt>type="built-in"</tt></h3>
<p>There are two built-in sceneries in CRRCsim: Davis field and the slope at
Cape Cod. To render these sceneries, specify either <tt>DAVIS</tt> or
<tt>CAPE_COD</tt> as the value of the <tt>variant</tt> attribute of the
<tt>scene</tt> tag.</p>
<p>Rendering the Davis field scenery:</p>
<div class="fragment"><pre class="fragment">
<scene type="built-in" variant="DAVIS" />
</pre></div>
<p>Rendering the Cape Cod scenery:</p>
<div class="fragment"><pre class="fragment">
<scene type="built-in" variant="CAPE_COD" />
</pre></div>
<p>There's nothing more to configure for these <tt>scene</tt> variants.</p>
<h3>Model-based sceneries: <tt>type="model-based"</tt></h3>
<h4>Adding objects to the scenery</h4>
<p>Everything between <scene> and </scene> describes graphical
objects. The order of the objects is mostly not important but it may actually
influence: rendering speed, rendering effects of translucent objects,
vertical position of an objects if attribute <tt>above_ground="0"</tt>.
For faster rendering opaque object should be defined in order front-to-back,
while for best rendering quality translucent objects should be defined last
and ordered back-to-front.</p>
<p>The <tt>object</tt> tag loads a 3D model and adds it to the scenery.
A lot of different file formats are supported. AC3D files (.ac) and
(.3ds) should work quite well. In theory, the SSG library loads many more
formats (.x, .dxf, .ase, .atg, .mdl, .flt, .m, .md2, .obj, .tri, VRML), but
this is not yet tested with CRRCsim due to the lack of models. Other
SSG-based projects show that it works.</p>
<p>An object can be loaded once and then placed several times in the scenery.
This saves texture memory, because all textures are shared between the
instances of the object. There currently are two options to place objects in
the scenery: <tt>instance</tt> and <tt>population</tt>. An <tt>instance</tt>
adds a single copy of the object in a specific location, while a
<tt>population</tt> adds several copies of the object distributed over an
area of the scene.</p>
<h4>Object attributes</h4>
<p>A <tt>terrain</tt> attribute declares the object to be part of the terrain
contour. This means that the object will add to the terrain height at this
point and therefore be included in wind calculations. Be careful, each
<tt>terrain</tt> object will also increase the CPU workload more than
non-terrain-objects! The default value for the <tt>terrain</tt> attribute
is "1", so <tt>terrain="0"</tt> must explicitely be
specified to exclude an object from terrain height calculations.</p>
<p>A <tt>visible</tt> attribute declares the object to be visible.
Invisible objects are not rendered but they add to terrain height
and are thus included in wind calculation. They are used to define
collision boxes (see below).
A non-visible object which is also non-terrain is actually useless...
The default value for the <tt>visible</tt> attribute is "1".</p>
<p>The <tt>translucent</tt> attribute (default value "1")
influences how translucent objects (i.e. objects having alpha information)
are rendered.
The actual meaning depends on the object being terrain or non-terrain.</p>
<p>A terrain object with <tt>translucent="1"</tt> is rendered
translucent (using so-called alpha blending), while if <tt>translucent=
"0"</tt> then it is assumed that it shall be rendered fully
transparent and it only has the purpose of: a) being used for terrain height
and wind computations, b) hide objects behind it.
This is different from an invisible terrain object, which does not
hides objects further back.
Terrain objects with <tt>translucent="0"</tt> are in fact
intended to be used for terrain in photo-realistic sceneries, where
the visual apparence of the terrain is actually incorporated into the
skybox textures, but the terrain shall anyway mask objects located
behind it. In theory, setting <tt>translucent="0"</tt> allows
a faster rendering than leaving it to 1, while achieving the same
effects.</p>
<p>A non-terrain object with <tt>translucent="1"</tt> is also
rendered translucent (using alpha blending), but additionally all areas
with alpha < 0.1 (i.e. almost fully transparent) are discarded so that
objects behind stay visible. This allows rendering of objects with highly
transparent areas (e.g. a tree texture applied to a simple rectangle) without
unrealistically masking objects behind.
However, correct rendering of the translucency requires back-to-front
order, and rendering is slower.
If <tt>translucent="0"</tt>, instead,
the texture is assumed to be an on-off one (alpha either 0 or 1),
and only areas with alpha almost 1 are rendered as fully-opaque, while
other areas are discarded. This allow a similar but faster and fully
order-independent rendering of partially transparent objects (again think
about a tree as before), althoug with lower rendering quality.
Actually a trick is implemented which allows for a nice, order-independent,
artifact-free, although slower, rendering of partially transparent objects.</p>
<p>The <tt>cutout</tt> attribute declares the object to be automatically
rotated along its vertical (z) axis so to always face the viewer (i.e.
the x-z plane is kept parallel to the camera).
It is useful to render such things as trees using a low poly object
and a texture. As such it is typically used for non-terrain objects.
The default value for the <tt>cutout</tt> attribute is "0"</p>
<p>The <tt>shadow</tt> attribute declares that the object shall cast shadows.
So far casted shadow, for both airplanes and scenery objects, are computed
usign the "shadow volumes" algorithm.
The default value for the <tt>shadow</tt> attribute is "0"</p>
<h4>Instance</h4>
<p>Each instance must have position coordinates
(<tt>north</tt>|<tt>east</tt>|<tt>height</tt> or <tt>x</tt>|<tt>y</tt>|<tt>z</tt>)
and optional orientation parameters (<tt>h</tt>|<tt>p</tt>|<tt>r</tt> for heading,
pitch and roll).
North, east and height coordinates must always be specified as absolute world
coordinates (remember, the unit is "ft."). Heading, pitch and roll
are related to local body coordinates of the object (in degrees). The
orientation of the heading/pitch/roll rotations is similar to the
coordinate system used for the airplane model: heading specifies a rotation
around the vertical (z) axis, pitch rotates around the horizontal lateral (y)
axis, and roll rotates around the longitudinal (x) axis.</p>
<p>The additional attribute <tt>above_ground="1"</tt> may be used
to specify that the given height is to be intended above local ground level:
thus <tt>height="0"</tt> is a handy way to place the object right
on the ground (assuming that the origin of the 3D object model is located
at its lowest point). Note that by default <tt>above_ground="0"</tt>.</p>
<p>Here's a simple example:</p>
<div class="fragment"><pre class="fragment">
<object filename="freqboard.ac" terrain="0">
<instance north="20.0" east="-160" height="0" h="90" p="0" r="0" />
</object>
</pre></div>
<p>This frequency board is located 20 feet north and 160 feet west of the
scene origin. It faces east (it is rotated 90 degrees around the vertical
axis). The board is excluded from height calculations. </p>
<h4>Population</h4>
<p>Objects in a population are distributed regularly (like a matrix of objects)
in a parallelogram-shaped area of the scene.
One vertex of the parallelogram is the origin of the area,
whose position in absolute world cordinates is specified by
(<tt>north</tt>|<tt>east</tt>|<tt>height</tt> or <tt>x</tt>|<tt>y</tt>|<tt>z</tt>).
The two sides of the parallegram exiting from the origin are given by vectors
(<tt>d1_north</tt>|<tt>d1_east</tt>|<tt>d1_height</tt> or
<tt>d1_x</tt>|<tt>d1_y</tt>|<tt>d1_z</tt>) and
(<tt>d2_north</tt>|<tt>d2_east</tt>|<tt>d2_height</tt> or
<tt>d2_x</tt>|<tt>d2_y</tt>|<tt>d2_z</tt>). Every component of d1 and d2 vectors
defaults to 0.</p>
<p>The total number of objects in the population is <tt>n1</tt> times <tt>n2</tt>,
with <tt>n1</tt> the number of objects along each line parallel to edge d1, and
<tt>n2</tt> the number of objects along each line parallel to edge d2.</p>
<p>The regular distribution of the objects may be perturbed to make it somewhat
irregular, hence more "natural". Spacing in d1 and d2 directions may be perturbed
by <tt>d1_noise</tt> and <tt>d2_noise</tt>, with location being altered by up to
+/-0.5 times noise value.</p>
<p>The size of the objects can be altered too (bigger/smaller) as well as their
vertical dimension (taller/shorter) and horizontal dimension (fatter/slimmer)
specifying respectively non-zero <tt>s_noise</tt>, <tt>sz_noise</tt> and
<tt>sx_noise</tt>. Size noise values are in percentage of original object size.
They all sum-up to define actual object size and shape.
Note that overall scale noise only reduces object size, while x and z scale noise
perturbes object size both increasing and reducing the respective original
dimension.</p>
<p>The additional attribute <tt>above_ground="1"</tt> is again used
to specify that the given height is to be intended above local ground level.</p>
<p>Here's a simple example:</p>
<div class="fragment"><pre class="fragment">
<object filename="populus_nigra.ac" terrain="0" cutout="1">
<population above_ground="1"
north="-450" east="500" height="0"
n1="61" d1_north="900" d1_east="0" d1_noise="3"
n2="9" d2_north="0" d2_east="240" d2_noise="3"
s_noise="0.03" sx_noise="0.05" sz_noise="0.05"/>
</object>
</pre></div>
<p>This is a small woods occupying a rectangular area of size 900x240 feets, the longer
edge being aligned in north-south direction. The trees are distributed along 9 rows
of 61 trees each. The location of each tree is perturbed up to +/-1.5 feets in each direction.
Tree size may be reduced up to 3%; additionally, tree may be taller/shorter or
larger/thinner by up to +/-2.5%. The trees are excluded from height calculations.
In fact they are simple 2D images, as indicated by the attribute
<tt>cutout="1"</tt>. A collision box (see below) will likely be specified
subsequently. Note that because using <tt>above_ground="1"</tt> the
collision box must in fact be specified AFTER the population, otherwise it will sit
on top of the collision box!</p>
<h4>Collision boxes</h4>
<p>If you exclude complex models from being part of the terrain by setting
<tt>terrain="0"</tt>, the airplane can fly right through them.
The usual solution for this issue is to add a collision box to the scene.
A collision box is an object of very low complexity that is not rendered
(so it is not visible in the scenery). Instead it is only used for collision
detection and height calculation (hence wind calculation as well).</p>
<p>Although the term "collision box" is widely used for this kind
of object, their shape is not limited to boxes. In theory, arbitrary objects
can be loaded, but please bear in mind that the goal of using collision boxes
is to reduce the triangle count for collision detection, so using a box,
a pyramid or a similar low-poly shape is a good idea.</p>
<p>The objects can have arbitrary material properties, colours or textures.
CRRCsim will exclude them completely from the rendering stage, so the models
don't have to be transparent. But textures and materials will consume memory,
so the collision objects should be made from a single material without a
texture.</p>
<p>To add an object as a collision box, simply set the <tt>visible</tt>
attribute of an object to "0":</p>
<div class="fragment"><pre class="fragment">
<!-- A collision box for a static aircraft model -->
<object filename="aircraft_collbox.ac" visible="0">
<instance north="-70.0" east="60" height="0" h="45" />
</object>
</pre></div>
<p>The default value for the <tt>visible</tt> attribute
is "1", so <tt>visible="0"</tt> must explicitely be
specified to make an object invisible.</p>
<h4>Embedded attributes</h4>
<p>Instead of adding two separate objects for the visible representation and
the collision box/terrain height, you can combine both objects in a single 3D model file.
To tell CRRCsim which parts of the 3D model shall be visible and which parts belong
to the terrain (collision box), make use of the node naming feature of your 3D modelling
tool. CRRCsim will treat everything up to the first space character as the
part's real name, everything else is interpreted as an attribute. Each attribute
consists of a plus or minus sign followed directly by a keyword. The following
attributes may be changed within an object file:</p>
<table border ="1">
<tr><th>Attribute</th>
<th>Effect</th></tr>
<tr><td>+terrain</td><td>Include this part in height-of-terrain calculations</td></tr>
<tr><td>-terrain</td><td>Exclude this part from height-of-terrain calculations</td></tr>
<tr><td>+visible</td><td>Include this part in the rendering (make it visible)</td></tr>
<tr><td>-visible</td><td>Exclude this part from rendering (make it invisible)</td></tr>
<tr><td>+translucent</td><td>Translucent (alpha blending) rendering</td></tr>
<tr><td>-translucent</td><td>Non-translucent (fully opaque or fully transparent) rendering</td></tr>
</table>
<p>Note that the attributes optionally assigned to each individual object in the file
override the default setting specified in the scenery file. Also note that the
<tt>cutout</tt> attribute cannot be altered within a file.
Additionally, only the <tt>-shadow</tt> attribute can be used within a file
to avoid an object casting shadows, however by default NO object will cast shadow unless
the <tt>shadow = 1</tt> attribute is specified in the scenery description.
The use of <tt>+shadow</tt> embedded attribute has no effect in this respect.</p>
<p>For example, in Blender, each part of a model is called an "object". You
can assign individual names to each object. Let's assume that you model a picnic
table to be placed in your scenery. Create a new object and call it "table -terrain"
(object panel, edit the datablock name field to read "OB:table -terrain").
Model your table. Then create a new object, call it "box -visible" and
model the collision box. Select table and box and export both to an AC3D model.
Then add this model to your scenery file in the usual way, but don't specify
any "terrain" or "visible" attributes in the XML file.
CRRCsim will automatically make the box invisible and ignore the table for
height calculations.</p>
<h2>10 End of file</h2>
<div class="fragment"><pre class="fragment">
</crrcsimSceneryFile>
</pre></div>
</body>
</html>
|
