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[Nel] Landscape generation pipeline

From:Cyril 'Hulud' Corvazier Subject:[Nel] Landscape generation pipeline Date:Fri, 19 Oct 2001 20:35:20 +0200

Hi there,

Here is a small guideline to generate landscape for NeL:

The landscape is done in 2 steps:

First step : artist creation of landscape data (textures and geometry) Second step : offline processing of final data

1. ----- Creation process

a) Draw some tiles

Tiles are textures that will be applied on the landscape. Tiles size can be 128x128 or 256x256. A 128x128 tile will be used to map a 2x2 meter aera. They are 24bits TGA files. Tiles are grouped by tileset. Contraints for tiles in the same tileset: -> The up and down pixel border of tiles must be the same. -> The left and right pixel border of tiles must be the same.

You will need some 8 bits TGA textures to make smooth transitions between tileset. This special "transition tiles" are 128x128. To complete all possible transitions you need 48 alpha textures. In fact, only 12 are needed with some rotations.

You will need displacement tiles too. Displacement tiles are like bump maps. They are 8 bits TGA file of 32x32 pixels. Each tileset can have 16 differents displacement tiles.

To know more about how to draw your texture tiles and alpha tiles, check the following document:

http://www.nevrax.org/download/examples/tile_bank.doc (330 ko)

b) Build a tilebank file

The tilebank file is edited with tile_edit.exe. The project is cvs/code/nel/tools/3d/tile_edit

• You will setup your tilesets by listing your bitmaps. Note that pixel checks are made at this step to check constraints describle above.
• You have to list your transition textures. There is a button "batch load" to load all your transition tiles in one time if the file name is normalized ( alpha_trans_00.tga alpha_trans_01.tga where the number follow the convention gived in tile_bank.doc).
• You have to list your displacement tiles too.
• You have to define one or several land. A land is a set of tileset.

Here is snowballs's tilebank with its textures (i have added some bumpy displacement map) :

http://www.nevrax.org/download/examples/tilebank.zip (3 Mo)

Don't forget to change the absolute path of the bank in tile_edit. Or you will not be able to see the texture in the tool.

At the question "What the tile set's children are for ?" the answer is : nothing, it is obsolete :)

c) Build the zones geometry

Ok, now we have to build some geometry for our landscape.

As you probably know, NeL landscape is based on Bezier quad patches. Bezier patches are more flexable than height field. you can make creases, concave elevations, holes etc.. Bezier patches are edited in 3dsmax using editpatch. The landscape is divided in zones. A zone is an area of 160x160 meters. Each zone is a patch mesh of 3dsmax. The vertices at the boundary of the zone must be snapped. They will be welded in the post process.

The zone name is like: 3_aa.zone The name is composed of a numeric coordiante (NUM = 3) and a alpha one (ALPHA = aa = 0) The upper left corner of the zone coordinate is : X = 160 * ALPHA Y = 160 * - NUM

For examples, a snowball zone is called 4_ac.zone, it means its upper left coordinates are ( 320, -480 )

d) Paint the zone with tiles

A patch is composed 16x16 tiles. Tiles are our 128x128 textures. A 256x256 textures is 2x2 tiles.

Once you have modeled your zones, you will have to paint it with textures and colors.

Before painting, you must set the bank you want to use it in 3dsmax. To do so, use the utility plugin called "NeL Tile Bank". Choose your bank on your hard disk. (Don't forget to set the absolute path of the bank in tile_edit). No need to "Setup material". If you do this, the plugin will generate a material per tile and try to map patches with it. When your bank become big, this take a lot of resources.

Now convert your patch mesh using the "NeL convert" modifer. Now your object is a NeL patch mesh and not a patch mesh. Now add a painter modifier. You can paint.

You can paint over several patch meshes by adding a paint modfier over several NeL patch meshes.

Now you should see the patch painter in a NeL window. Main commands are:

F1: Tile mode, paint textures F2: Color mode, paint vertex color F3: Displace mode, paint displace textures A: automatic lighting on / off.(to see the displacement, a little slow) SPACE: choose your texture, colors or displace to paint.

etc...

See cvs\code\nel\tools\3d\plugin_max\nel_patch_paint\user_guide.txt for other commands. You can configure it by editing the keys.cfg file.

Check some snowballs zones max project: http://www.nevrax.org/download/examples/snowballs_zones.zip (1 Mo)

Note that to do that kind of work, you need a modifier you don't have : edit patch for NeL patch meshes. The reason is it is based on Discreet source code. With nomal edit patch you can subdivide patches, extrude, bievel etc.. You can't for example, change the number of tiles on a patch.

e) Performance issues

Some notes about performances:

• You can make a lot of zone. I can't tell you the zone count for our project, but it is high :)
• 700 128x128 textures is a good count. (Use DXTC5 !)
• 50 patches of 16x16 tiles per zone is the max peek you should use. Equivalent to 200 patches of 8x8 tiles.
• A tile should be 2x2 meters on the ground. It give you 1.5 centimeter pixel ratio. Double than quake 3 walls but on a landscape ! So with the given patch count, you have twice the surface of the zone to model it.

Now your zones are modeled, painted, colored and displaced. Time for processing.

1. ----- Offline process--

The offline processing project is in cvs in

cvs/code/nel/tools/3d/landscape_builder

How to build the NeL landscape.

a) What does mean 'Build the NeL lanscape' ?

Once you have created your tile bank and your landscape zones, you will need to preprocess your zone in order to:

• Weld the boundary vertices of the zones
• Light the zones with shadows casted by the landscape and the static objects (like trees, buildings..)

b) Requirement

Before building the landscape you must have:

• Installed Cygwin tools and set the PATH properly. (Under windows)
• Compilated some binaries and putted them in the "bin/" folder. (zone_dependencies.exe, zone_welder.exe, zone_lighter.exe. zone_smoother.exe is not use anymore)

c) Data exportation

You have to export those data:

• The .zone files in the "zone_exported/" folder. (NeL landscape zone files exported from 3dsmax)
• The .bank file in the "bank/" folder. (NeL bank edited with tileedit)
• The .ig files (named like the zone) in the folder "ig/". (NeL instance group file exported from max)
• The .shape files (for trees, building or every things that cast shadows on the landscape) in the folder "shaped/"
• The .tga files (for the shapes used for alpha blending and for displace tiles) in the folder "maps/"

d) Configure

Configure the cfg/properties.cfg file.

e) Computing

• 0_clean_all.bat - clean all the directories.

• 1_build_dependencies.bat - build dependencies files. Each zone will have a dependency file in which is listed the zone that cast shadow on it. -> generate the .depend file in the folder zone_depend/

• 2_weld.bat - Weld the zones. -> generates the .zonew files in the folder zone_welded/

• 3_light.bat - Light the zones. -> generates the .zonel files in the folder zone_lighted/

All the building process in incremental, ie, if you modify only ONE .zone file, the weld pass will modify the zonew file and each neighbors of this zone. The light pass will relight only the .zonew modified files.

The .zonel files are the final zone files. They are loaded by the engine. (see snowballs 2 source code for detail).

f) farbank building

You will need to compute a farbank. The farbank is the bank used to map the patches when they are far. This bank is computed with the .bank file and the tiles texture. see the project: cvs/code/nel/tools/3d/build_far_bank

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I hope this first document will help you. All the Nevrax team is ready to reply to your questions and comments.

Regards,

Cyril Corvazier

Lead 3d programmer Nevrax France

https://mail.gnu.org/archive/html/nel-all/2001-10/msg00052.html