1<html> 2 3<head> 4 <title> 5 Fracplanet user manual 6 </title> 7 <meta name="keywords" content="Fracplanet, user documentation, user manual"/> 8 <meta name="description" content="Fracplanet user documentation"/> 9 <link rel="stylesheet" title="Default styles" type="text/css" href="fracplanet.css" media="screen,print"/> 10</head> 11 12<body> 13 14<h1> 15 Fracplanet user manual 16</h1> 17 18<h2>Introduction</h2> 19 20<p> 21 Fracplanet is an application to generate simple random planets and terrain 22 with oceans, mountains, icecaps and rivers. 23 Parameters are specified interactively and the results displayed using OpenGL. 24 The generated objects can be exported in formats directly usable by POV-Ray or Blender, 25 or as more generally useful texture images. 26</p> 27 28<h2>Command line arguments</h2> 29 30<p> 31 Some command line arguments (not listed here) are intercepted and interpreted by Qt. 32 These are pretty much what you'd expect most X11 applications to handle 33 e.g <code>-geometry <em>X</em>x<em>Y</em></code>. 34 Fracplanet's own command line arguments are: 35</p> 36 37<dl> 38 <dt>--help, -h</dt> 39 <dd> 40 Display a list of recognised arguments. 41 </dd> 42 <dt>--verbose, -v</dt> 43 <dd> 44 Output information about fracplanet execution (and OpenGL) to stderr. 45 </dd> 46 <dt>--display-list, -d</dt> 47 <dd> 48 Start up the application with rendering in display list mode by default 49 (c.f immediate mode). 50 This is particularly useful when the application is running remotely as the 51 generated meshes are then only sent to the local OpenGL display hardware once. 52 </dd> 53 <dt>--invert-mouse-y, -y</dt> 54 <dd> 55 Start application with mouse in non-joystick mode for flight. 56 </dd> 57 <dt>--wireframe, -w</dt> 58 <dd> 59 Start application with rendering set to wireframe mode. 60 </dd> 61</dl> 62 63<h2>GUI</h2> 64 65<p> 66 The main part of the fracplanet GUI is a tabbed control. 67 The terrain generated is shown in a separate window (which disappears while regenerating). 68 A progress dialog is generally displayed while generating terrain (except during application startup). 69</p> 70 71<h3>Create tab</h3> 72 73<p> 74 Note that none of the parameters adjustable on this tab have any effect on the displayed model until one of 75 the "Regenerate" buttons is pressed. This tab is further subdivided into sub-tabs 76 ("Terrain", "Snow", "Rivers", "Colours", "Clouds"). 77</p> 78 79<h4>Terrain</h4> 80 81<p> 82 This tab is actually even further subdivided 83 ("Basics", "Subdivision" and "Noise" tabs), 84 but the list below doesn't distinguish. 85</p> 86 87<dl> 88 <dt>Starting geometry: Generate...</dt> 89 <dd> 90 A pull-down menu (or "combo-box") selects the initial geometry which will be "fractalized". 91 Planet creates planets by subdividing an icosahedron. 92 The other terrain area type create planar terrain areas by subdividing one or more triangles. 93 Note that the square type doesn't produce very good results because the triangles it uses aren't equilateral. 94 </dd> 95 <dt>Base land height</dt> 96 <dd> 97 This expresses the initial height of the terrain (relative to the sea level) as a percentage of the vertical maximum perturbation size. 98 Negative values produce (on average) more ocean than land, positive values produce more land than ocean. 99 </dd> 100 <dt>Terrain random seed</dt> 101 <dd> 102 Specifies the random number generator seed used when creating terrain. 103 Regenerating without changing this value will produce the same terrain, allowing the user to play with subdivision levels, colours etc while still retaining the same basic pattern of oceans and continents. 104 The value is initially set to the system time on application start-up. 105 </dd> 106 <dt>Power law</dt> 107 <dd> 108 A power law applied to all above-sea-level heights after terrain generation. 109 (This consists of normalising the height relative to the maximum height in the terrain model and raising it to the power of this number divided by 100). 110 Values above 100 flatten low terrain, tending to produce smooth plains surrounding spiky mountains. 111 Values below 100 flatten high terrain, tending to produce smooth highlands surrounded by steep cliffs. 112 </dd> 113 <dt>Subdivisions</dt> 114 <dd> 115 The number of subdivisions of the initial structure. 116 Each successive level of subdivision increases the number of triangles by a factor of four, so users should increase this parameter with caution. 117 This has a major impact on the amount of memory consumed, the frame rate and the responsiveness of the application. 118 </dd> 119 <dt>Unperturbed subdivisions</dt> 120 <dd> 121 Specifies the number of the subdivisions which will be performed <em>without</em> random perturbation of the vertices. 122 Lower numbers (0, 1) produce a few large continents. 123 Higher values produce many small islands. 124 </dd> 125 <dt>Vertical perturbation</dt> 126 <dd> 127 Specifies the maximum size of vertical perturbations at the first level of subdivision. 128 The maximum perturbation size is then halved at each subsequent subdivision. 129 Planets and terrain areas both have a nominal radius of 1.0, 130 and the number here is divided by 100 so if you specify a vertical variation of 12 you could get mountains which are on the order of 12 percent of the planet's radius high, or larger if subsequent perturbations accumulate upwards at a point (of course suppressing initial large perturbations using the "Unperturbed" parameter will tend to reduce this). 131 This is of course a ridiculous height for mountains on anything but an asteroid, but using realistic values will just produce very boring looking planets. 132 </dd> 133 <dt>Horizontal perturbation</dt> 134 <dd> 135 Specifies the maximum size of horizontal perturbations at the first level of subdivision. 136 The maximum perturbation size is then halved at each subsequent subdivision. 137 Beware of making this value too large as it can produce overhanging/self-intersecting terrain, 138 on the other hand small values can be useful for breaking up obvious artifacts of the initial geometry. 139 </dd> 140 <dt>Noise terms</dt> 141 <dd> 142 Number of terms in a Perlin noise function added to the terrain heights. 143 Each subsequent term doubles the frequency. 144 The best way to get an appreciation of the qualitative differences between Perlin noise and 145 subdivision-perturbation is to reduce "Vertical perturbation" (on the "Subdivision" tab) 146 to zero and increase the number of noise terms. 147 </dd> 148 <dt>Noise frequency<dt> 149 <dd> 150 Frequency of 1st noise term. 151 100 gives a scale on the order of the terrain radius. 152 Subsequent terms double the frequency (and therefore halve their length scale). 153 </dd> 154 <dt>Noise amplitude<dt> 155 <dd> 156 Amplitude of 1st noise term, as a percentage of the nominal object radius. 157 </dd> 158 <dt>Noise amplitude decay rate<dt> 159 <dd> 160 The amplitude of subsequent noise terms decays to this percentage of the amplitude of the previous term. 161 Fifty percent does the classic fractal thing of scaling perturbation size with length scale. 162 Increasing it slightly (to e.g sixty percent) has the interesting effect of making rivers meander more 163 as small-scale variations now have a bigger effect on local gradients than large scale features. 164 </dd> 165</dl> 166 167<h4>Snow</h4> 168 169<dl> 170 <dt>Snowline at equator</dt> 171 <dd> 172 The nominal height of the snowline at the equator of a planet (and everywhere on a flat-based terrain area), 173 expressed as a percentage of the maximum height of the terrain. 174 </dd> 175 <dt>Snowline at pole</dt> 176 <dd> 177 The nominal height of the snowline at the poles of a planet (unused for a flat-based terrain area), 178 expressed as a percentage of the maximum height of the terrain. 179 </dd> 180 <dt>Snowline power law</dt> 181 <dd> 182 Tweaking this parameter lets you control whether the snowline remains high up and only plunges 183 downward towards the poles, or whether it only quickly rises near the equator. 184 Experiment, it has a fairly subtle effect. 185 </dd> 186 <dt>Snowline slope suppression</dt> 187 <dd> 188 The larger this value is, the harder it is for snow to stick to steep slopes 189 (you can see this effect for real on any mountain range). 190 This breaks up the snowline quite nicely, as it otherwise tends to stop at 191 an artificially uniform height (reduce this parameter to zero to see what I mean). 192 </dd> 193 <dt>Snowline glacier effect</dt> 194 <dd> 195 If this parameter is positive, rivers tend to form glaciers and you 196 will see e.g white lines running out of snowy areas, and frozen lakes. 197 If this parameter is negative rivers find it harder to freeze and 198 you will see them running through snowy areas and forming un-frozen lakes. 199 </dd> 200</dl> 201 202<h4>Rivers</h4> 203 204<dl> 205 <dt>Rivers</dt> 206 <dd> 207 Specifies the number of rivers to be generated. 208 Note that rivers starting in the sea are immediately abandoned, but still count against this number 209 (this is so the relative proportions of land/ocean can be tweaked without affecting the river source density). 210 Rivers run from vertex to vertex along triangle edges, and are then rendered by blending from the 211 river vertex colour to the surrounding terrain colour. 212 This isn't ideal as they aren't very sharply defined. 213 A previous version of the software flowed rivers from triangle to triangle 214 which produced nice solid edged rivers (like the oceans are) 215 but since they weren't flat it wasn't ideal either. 216 </dd> 217 <dt>Rivers seed</dt> 218 <dd> 219 Random number seed for river generation. 220 If you change this, but not the perturbation seed, you can get a different river network on the same terrain. 221 </dd> 222 <dt>Lake becomes sea</dt> 223 <dd> 224 As a river is flowed across a terrain, it will sometimes form a lake as the water 225 level rises sufficiently to overcome a terrain barrier. 226 If the lake becomes sufficiently large (greater than the percentage of available surface area specified here) 227 then it is considered to have become an inland sea and it is no longer necessary for the lake to rise until 228 an outflow to be discovered (in the real world, surface evaporation replaces the outflow). 229 Increasing this number may result in larger lakes, but the process of river generation can 230 take considerably longer. 231 </dd> 232</dl> 233 234<h4>Colours</h4> 235 236<dl> 237 <dt>Change colours</dt> 238 <dd> 239 Click on these buttons to bring up a colour-picking dialog and change the colour for the selected class of terrain. 240 Each button displays the colour currently selected for that class. 241 Obvious things you might want to do are to change the shoreline colour to 242 the same colour as the low level terrain (those beaches are pretty absurdly <em>wide</em> otherwise), 243 change the orange highlands to a more mountainous grey, or perhaps you preferred 244 an apocalyptic "lava world" with red rivers and oceans (use emission to make them glow), 245 black shorelines and ash-grey terrain. 246 </dd> 247 <dt>Oceans and rivers emissive</dt> 248 <dd> 249 Sets the emission (also called "glow") of lakes and rivers, on a scale of 0-100. 250 This is mainly to facilitate glowing lava planets. 251 Note that for terrain generated with emission non-zero, 252 an alternative OpenGL rendering path must be used which may be a little slower. 253 </dd> 254</dl> 255 256<h4>Clouds</h4> 257 258<p> 259 The cloud layer, when generated, is a triangle mesh with variable 260 translucency at each vertex. 261 Note that it's <em>not</em> a texture in the normal sense. 262</p> 263 264<dl> 265 <dt>Clouds enabled</dt> 266 <dd> 267 Select the check box to trigger creation of a cloud layer. 268 </dd> 269 <dt>Subdivisions</dt> 270 <dd> 271 When left unchecked, the cloud layer will be subdivided 272 to the same degree as the terrain. 273 Check the box for explicit control of cloud layer subdivision. 274 </dd> 275 <dt>Clouds seed.</dt> 276 <dd> 277 Change this to get a different cloud pattern. 278 </dd> 279 <dt>Cloud height</dt> 280 <dd> 281 Change this to get adjust the height of the clouds above the terrain. 282 </dd> 283</dl> 284 285<h4>Other "Create" tab controls</h4> 286 287<dl> 288 <dt>Generate</dt> 289 <dd> 290 Click this button to regenerate the planet/terrain area <em>without changing the random seeds</em>. 291 </dd> 292 <dt>...new rivers seed</dt> 293 <dd> 294 Click this button to increment the river generation seed by one and regenerate. 295 This gets you the same landscape with a different river network. 296 </dd> 297 <dt>...new terrain seed</dt> 298 <dd> 299 Click this button increment the terrain seed by one and regenerate. 300 This will get you a completely different terrain. 301 (The river network will be different too, although it's seed won't have changed, as the rivers flow over the terrain differently). 302 </dd> 303 <dt>...new clouds seed</dt> 304 <dd> 305 Click this button increment the clouds seed by one and regenerate. 306 This will get you a different cloud layer. 307 </dd> 308</dl> 309 310<h3>Render tab</h3> 311 312<p> 313 Options controlling OpenGL rendering appear on this tab. 314 Generally none of these makes any difference to the state of the rendered mesh. 315 However, some of the parameters do affect some export methods; see the individual item descriptions. 316</p> 317 318<dl> 319 <dt>Wireframe checkbox</dt> 320 <dd> 321 Selects OpenGL wireframe rendering mode. 322 </dd> 323 <dt>Joystick mouse checkbox</dt> 324 <dd> 325 This simply affects whether, when in flight mode, pulling the mouse down the screen flies you in that 326 direction, or whether it's more like an aircraft joystick and pitches you up instead. 327 </dd> 328 <dt>Display list</dt> 329 <dd> 330 Selects OpenGL display list rendering. 331 Display list rendering is generally but not always faster 332 (depends on your OpenGL implementation and graphics drivers). 333 The main reason display list rendering is not enabled by default is that 334 the application may pause for a long time while OpenGL processes the 335 list when it is first rendered; the amount of additional memory 336 consumed by the display list is also a problem for very large meshes. 337 </dd> 338 <dt>Background colour</dt> 339 <dd> 340 Colour picking buttons to control the colour used for the viewing area background. 341 The low altitude colour is also used when exporting a cloud mesh to blender. 342 </dd> 343 <dt>Ambient</dt> 344 <dd> 345 The amount of ambient illumination. 346 This is also used when exporting shaded textures. 347 </dd> 348 <dt>Illumination azimuth and elevation</dt> 349 <dd> 350 Control the illumination direction. 351 These are also used when exporting shaded textures. 352 </dd> 353 <dt>Status</dt> 354 <dd> 355 A text field displaying information about the rendered mesh, 356 and rendering performance (recent average frames-per-second). 357 </dd> 358</dl> 359 360<h3>Save tab</h3> 361 362<p> 363 Strictly speaking it's Export which is provided, not save, as fracplanet's state cannot be restored (yet). 364 There are currently three ways of exporting models from fracplanet for other uses: to POV-Ray, to Blender and as textures. 365</p> 366 367<h4>POV-Ray</h4> 368 369<dl> 370 <dt>Add atmosphere</dt> 371 <dd> 372 This tick-box causes additional POV-Ray directives to be emitted to render a thin layer of atmosphere. 373 </dd> 374 <dt>Sea object</dt> 375 <dd> 376 This tick-box causes a single sphere or infinite plane to generated 377 for the oceans <em>instead</em> of numerous individual triangles. 378 </dd> 379 <dt>Base filename</dt> 380 <dd> 381 Enter the filename root to be used here. 382 Two files will be generated, one with ".pov" appended, and one with ".inc" appended. 383 The .inc file actually contains the object (using POV-Rays's <code>mesh2</code> format), 384 plus any other objects generated due to the options above. 385 The .pov just includes the .inc and adds a camera and light source and was primarily intended for testing: 386 the expectation is that users will generally include the .inc into their own scenes, probably wrapping it 387 in a POV-Ray <code>union</code> with embedded translate/scale/rotate directives). 388 </dd> 389 <dt>Save (POV-Ray)</dt> 390 <dd> 391 Click this button to create the POV-Ray files. 392 This can take quite a long time so a progress bar is used to track the completed percentage. 393 </dd> 394</dl> 395 396<p> 397 There are additional comments on usage with POV-Ray <a href="#pov">below</a>. 398</p> 399 400<h4>Blender</h4> 401 402<dl> 403 <dt>Per vertex alpha</dt> 404 <dd> 405 This check box selects Fracplanet's preferred method for outputting clouds: 406 by specifying per-vertex alpha components. 407 However, Blender seems to ignore these so a workround is used and an opaque cloud layer is output 408 (which should be ok if you fly underneath it and light it sensibly). 409 You probably don't want to switch this on. 410 </dd> 411 <dt>Save (Blender)</dt> 412 <dd> 413 Click this button to create a file (a file dialog will appear) which can be imported into Blender. 414 Note that the save file takes the form of a Python script (traditionally a <code>.py</code> file extension) 415 which can be executed by Blender to reconstruct the fracplanet model. 416 </dd> 417</dl> 418 419<p> 420 There are additional comments on usage with Blender <a href="#blender">below</a>. 421</p> 422 423<h4>Texture</h4> 424 425<p> 426 Saving as texture(s) gives you a set of 2D images which can be used by other rendering or modelling applications, 427 if not immediately then perhaps after a little massaging with the ImageMagick or NetPBM tools. 428 On saving you'll be prompted for a base <i>filename.ppm</i>. A number of files are then saved: 429</p> 430 431<dl> 432 <dt>filename.ppm</dt> 433 <dd> 434 The basic texture. 435 This will be embedded in black pixels if the terrain isn't square e.g for the hexagonal terrain area. 436 Planets produce a cylindrically projected latitude-longitude "spheremap". 437 </dd> 438 <dt>filename_dem.pgm</dt> 439 <dd> 440 The height field (a "DEM" is a Digital Elevation Model). 441 This is output as a PGM image, with heights from 0.0 to 1.0 scaling to 0 to 65535. 442 If the DEM contains a value greater than or equal to 256 443 (highly likely, except for exceptionally flat terrains), 444 then it will be output as a 16-bit PGM which, while part of the PGM 445 <a href="http://netpbm.sourceforge.net/doc/pgm.html">"standard"</a> 446 isn't well supported by many common graphics tools which appear to otherwise offer good PPM support 447 (e.g The Gimp doesn't like it). 448 The NetPBM tools are your best bet to convert this to something else (e.g pnmdepth). 449 Imagemagick's simple "display" tool also handles them well, scaling the maximum value to white. 450 </dd> 451 <dt>filename_norm.pgm</dt> 452 <dd> 453 The surface normals; XYZ components are mapped to RGB; [-1, 1] is scaled to [0,255]. 454 It is thought this should be useful for bump-mapping renderers (e.g 455 <a href="http://www.shatters.net/celestia/">Celestia</a>) where the 456 illusion of surface relief is produced by normal perturbation. 457 If you intend to use this file, you almost certainly want to disable shading (see below), 458 as your renderer will compute it later. 459 </dd> 460</dl> 461 462<p> 463 Other texture save options: 464<p> 465 466<dl> 467 <dt>Shaded texture</dt> 468 <dd> 469 Controls whether the texture map includes the effect of lighting. 470 If you intend to use the information in the _norm.ppm or the _dem.pgm files to subsequently compute lighting, 471 then you almost certainly do <em>not</em> want the output texture to be shaded. 472 The amount of ambient lighting is taken from the slider on the render tab. 473 (Disabling shading is the same effect as setting ambient to 1.0). 474 The lighting direction is controlled by the render tab's illumination azimuth and elevation controls. 475 If you want to use the OpenGL window to preview the lighting, you should set zero spin and tilt 476 by hitting the "reset"button and dragging the tilt to the centre (unfortunately, this 477 gives you an edge-on view of flat terrain areas so it may be necessary to use the "fly" mode). 478 </dd> 479 <dt>Texture height</dt> 480 <dd> 481 The number of pixels high the saved texture images are. 482 The width is implicitly determined by the height. 483 For flat terrain the width is the same as the height. 484 For planets the width is twice the height because the height spans [-90,+90] degrees latitude, 485 and the width spans [-180,180] degrees longitude. 486 </dd> 487</dl> 488 489<p> 490 There are additional comments exported texture usage <a href="#texture">below</a>. 491</p> 492 493 494<h3>About tab</h3> 495 496<p> 497 This tab displays information about the software (in particular the version number) and its license. 498 There is a button to show a dialog containing user documentation, 499 and another button to display information about the Qt toolkit. 500</p> 501 502<h3>Display window</h3> 503 504<p> 505 The display window, when shown, shows the current 506 (most recently generated) terrain model. 507 It is hidden when terrain is being regenerated or saved. 508 The (badly named) "tilt" slider controls the latitude of the camera (when viewing a sphere-based object), 509 and the elevation (as in azimuth-elevation) of the camera when viewing a planar based terrain area. 510 Note that in the latter case the bottom half of the slider places the camera below base ground level/sea level, 511 which results in little being seen due to back-face culling. 512 The "spin rate" controls the rate at which the object is rotated. 513 The display window update rate is clamped to 60Hz, although this will typically 514 only be reached at the lower levels of subdivision. 515</p> 516 517<p> 518 Hitting the "Fly" button puts you into free-flight mode. 519 Pitch and yaw are controlled by the mouse position relative to the window centre 520 (if the pitch control feels backwards, invert mouse-Y behaviour on the render tab). 521 Roll is controlled by left/right mouse buttons, or the keyboard left/right arrow keys. 522 Speed is controlled by the mouse wheel or the keyboard up/down arrow keys. 523 Hit Esc to return to the normal viewing mode. 524</p> 525 526<h2>Fracplanet exports: usage notes</h2> 527 528<a name="pov"><h3>POV-Ray</h3></a> 529 530<p> 531 To ray-trace a saved terrain (saved as terrain.pov and terrain.inc, say) do:<br/> 532 <code>povray -Q9 -geometry 768x576 terrain.pov</code><br/> 533 Expect to get MANY "determinant too small" messages, 534 especially when using high degrees of subdivision. 535 It used to take POV-Ray a LOT longer to read large models than 536 to render them, but it seems to load much faster these days. 537</p> 538 539<p> 540 Note that clouds, if generated, are output using POV-Ray's <code>double_illuminate</code> 541 and <code>no_shadow</code> declarations. 542 <code>double_illuminate</code> means that both sides of clouds are the same colour 543 (rather than the underside being black). 544 <code>no_shadow</code> means that the clouds cast no shadow on the ground 545 (where the clouds are solid, the shadows are completely black, which looks more unnatural than no shadows). 546 If desired, the declarations can be found at the end of the saved .inc file and simply edited out. 547</p> 548 549<p> 550 (The author currently uses POV-Ray 3.6). 551</p> 552 553<a name="blender"><h3>Blender</h3></a> 554 555<p> 556 The easiest way to load mesh saved for blender is with blender's <code>-P <filename.py></code> 557 command line argument on startup. 558 Note that you'll have to remove blender's default initially created object to see much of the fracplanet object. 559 Also, its shading won't look much like it did in fracplanet until you change blender's viewport shading mode to 560 something better than the "solid" default. 561</p> 562 563<p> 564 Blender consumes an alarming amount of memory. 565 Even loading a planet generated with fracplanet's default five levels of subdivision 566 consumes a quarter of a gigabyte of RAM. 567 It would probably help if fracplanet made some effort to optimise its meshes, 568 and/or made use of textures rather than trying to do everything using geometry, but it doesn't yet. 569</p> 570 571<p> 572 Blender's per-vertex-colours capability seems to ignore the alpha component of per-vertex colours, 573 with the result that the cloud layer is rendered as a solid opaque colour. 574 <em>If anyone has a solution to this it would be gratefully received.</em> 575 Fracplanet's workround is to output an opaque surface with the blending 576 (with the "low altitude" colour from the render tab controls) already done. 577 The "per-vertex alpha" checkbox switches to the preferred behaviour in case it ever gets fixed. 578</p> 579 580<p> 581 Each mesh is output with 2 materials. 582 The clouds just use material 0. 583 For the terrain, material 0 is for land facets, material 1 for the sea. 584 This may be useful for users wanting to give them different shader properties. 585</p> 586 587<p> 588 In Blender, the terrain mesh is named "fracplanet.terrain". 589 There will also be a "fracplanet.cloud" if clouds were enabled. 590</p> 591 592<p> 593 Emissive terrain isn't supported. 594</p> 595 596<p> 597 If you want to manipulate the terrain, and know a bit of Python, 598 an easy way might be to edit the <code>.py</code> file; 599 at the start there are two functions defined: 600 <code>v</code> called to create each vertex 601 and <code>f</code> called to create each face. 602</p> 603 604<p> 605 (The author currently uses Blender 2.46). 606</p> 607 608<a name="texture"><h3>Texture Maps</h3></a> 609 610<p> 611 It is hoped that the texture export option will be of use to those building planets for 612 <a href="http://www.shatters.net/celestia/">Celestia</a>. 613 (The author hasn't tried it himself yet; at time of writing Celestia 614 is waiting to make it's way from Debian Unstable to Testing). 615 Celestia's texture formats are well documented at the 616 <a href="http://www.celestiamotherlode.net/catalog/documentation.html">Celestia Motherlode</a>, 617 in particular by the <a href="http://www.lns.cornell.edu/~seb/celestia/textures.html">Virtual Surface Textures</a> 618 document. 619 The main issues for anyone doing this would seem to be the need to reduce the height map from 16 to 8 bit 620 (easily changed by pnmdepth) and the possibility that fracplanet's normal map (if used, alternative Celestia 621 can compute normal maps from the height map) needs it's components exchanging or reflecting. 622 Celestia can also take a specular map, generally used to indicating the presence of reflective water (or snow); 623 fracplanet doesn't output this (yet) but it should be possible to fake something by processing the height or texture map. 624</p> 625 626<p> 627 As a simple demonstration of how to use a saved planet texture, here's how to use it as a spheremap in POV-Ray. 628 Save an unshaded <code>spheremap.ppm</code> from fracplanet, and do:<br/> 629 <code> 630 convert spheremap.ppm spheremap.png<br/> 631 convert -depth 8 spheremap_dem.pgm spheremap_dem.png<br/> 632 cat <<EOF > spheremap.pov<br/> 633 camera {perspective location <0,1,-4.5> look_at <0,0,0> angle 45}<br/> 634 light_source {<100,100,-100> color rgb<1,1,1>}<br/> 635 sphere<br/> 636 {<br/> 637 <0,0,0>,1<br/> 638 pigment { image_map {png "spheremap.png" map_type 1} }<br/> 639 normal { bump_map {png "spheremap_dem.png" map_type 1 bump_size 20.0} }<br/> 640 rotate <0,clock*360,0.0><br/> 641 }<br/> 642 EOF<br/> 643 povray spheremap.pov +KFI1 +KFF100 +W640 +H480 +Of.png<br/> 644 animate f???.png<br/> 645 </code> 646</p> 647 648<p> 649 <code>convert</code> is one of the ImageMagick utilities. 650 You could omit the line beginning "normal" but you will get a rather flat looking planet. 651 The factor of 20.0 at the end of the line is a rather arbitrary parameter. 652 Raise or lower it to adjust the apparent roughness of the planet. 653</p> 654 655<h2>License</h2> 656 657<p> 658 This program is free software; you can redistribute it and/or 659 modify it under the terms of the GNU General Public License 660 as published by the Free Software Foundation; either version 2 661 of the License, or (at your option) any later version. 662 663 This program is distributed in the hope that it will be useful, 664 but WITHOUT ANY WARRANTY; without even the implied warranty of 665 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 666 GNU General Public License for more details. 667 668 You should have received a copy of the GNU General Public License 669 along with this program; if not, write to the Free Software 670 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 671</p> 672 673<p> 674 The full license can be also viewed on fracplanet's "About" tab. 675</p> 676 677</body> 678
