Here are some ideas, tips, optimization hints and examples for VRML world builders.

Doom II worlds converted to VRML

Worlds for the DOOM II Game from ID-software are stored in a format that is convertable to VRML. In addition there are shareware and freeware tools available for editing and creating worlds for DOOM.

Original DOOM II worlds converted to VRML. The following list contains links to the original VRML file, an enhanced version using BSP tree optimizations and the multi-user version:

• Mission 1 - BSP optimized - multiuser
• Mission 2 - BSP optimized - multiuser
• Mission 3 - BSP optimized - multiuser
• Mission 4 - BSP optimized - multiuser
• Mission 5 - BSP optimized - multiuser
• Mission 6 - BSP optimized - multiuser
• Mission 7 - BSP optimized - multiuser
• Mission 8 - BSP optimized - multiuser
• Mission 9 - BSP optimized - multiuser

In BS Contact the textures will look better using "high quality" or "hardware" rendering settings. The C key toogles collision detection. the G Key gravitiy

How to build DOOM VRML worlds your self:

First you need to have DOOM II.

Get a free DOOM WAD Editor and construct your own DOOM WAD-Worlds. WAD Files and editing programs can be found on the Internet by searching for sites via keywords like "wad", "doom".

Convert the WAD File to VRML using the Doom2Wrl program.

Doom 2 wrl was created by Ken Russel, SGI. We used a modified version for converting to the proper multi-user coordinate scale, the source is available as zip-file. (Microsoft Visual C and JPEG Library required for compiliation.)

For tuned performance the generated VRML code can be BSP-Tree optimized for BS Contact.

The source of Doom2Vrml could be further enhanced to support things, monsters, teleporters and so on. Currently only some doors can be opened with a click.

Let us know if you enhanced doom2vrml.

Scripting examples:

Building large worlds

In the following are several approaches for different types of scenes.
Managing Rooms with a Proximity Sensor
A Script Node with a Proximity Sensor switches Rooms between an inside and outside view. Turn off collision detection ("C" Key in BS Contact) and move into out of the gray boxes (== outside view).
Managing Rooms with a BS Contact Occlusion Node
It's the same principle as above, but the BS Contact extension node Occlusion is being used. Occlusion would allow more complex Sensor areas composed out of primitives or even convex IndexedFaceSet's.

Scene preprocessing using the BS Contact BspTree Node

Please check the BSP documentation for more technical information about the BS Contact BspTree node.

Optimizations and performance Tips

• reduce and simplify geometry
• remove unneeded faces
• use instancing (DEF once USE many Times)
• don't disable backface culling (solid FALSE) if it is not totally necessary
• use unlit textures :

Shape {
appearance Appearance {
texture ImageTexture { url "myimage.jpg"}
}
geometry ...
}
• Share identical Texture, Material and Appearance nodes.
• limit the number of lights, Directional Lights are fastest
• help the browser by limiting the amount of active nodes:
• using a switch node currently unneeded / invisible parts can be enabled / disabled
• complex animations can be disabled  by disabling TimeSensor's ( e.g. enabled FALSE )

• Specify visibilityLimit in NavigationInfo for better z-range adaption and for more culled geometry
• Many Text Nodes are expensive, an alternative are textures representing text
• Few IndexedFaceSet's with many faces are more performant than many single face IndexedFaceSets with few or only a single face
• If the plugin is embedded into a frame set any animations like animated GIF's in the other frame may slowdown the 3D operation
• Flat shading can be forced with the default value for creaseAngle 0 and normalPerVertex FALSE
• For unlit materials use Material {diffuseColor 0 0 0 emissiveColor yourColorHere } The specularColor is already black by default.
• Prescale textures to a power of 2

• if using many rectangles each with a different texture, try to combine several textures in one image, and adapt texture coordinates
• color per vertex doesn't work in Direct3D Ramp Driver ("high speed"), in RGB/Hardware mode color per vertex Shapes are unlit.
• Shapes with more than 1024 (hardware) / 2020 vertices (software) or color per face requires some extra preprocessing
• animating vertex attributes (e.g. coordinates) of shapes works fastest up to the limit of 1024/2020 vertices
• try GIF Textures instead of JPEG's for Ramp Driver
• prefer modeling with convex polygons instead of generating an equivalent set of triangles

If the model is targeted to run on a software only OpenGL platform or OpenGL hardware without texture acceleration:

• limit the amount of textures
• prescale textures to a power of 2
• use colors per face or color per vertex to add surface detail

The "software only" rendering speed depends largely on the size of the rendering window. A VRML World could be presented using several viewing choices like:

• a small VRML window embedded in a HTML page
• a full screen VRML link for users preferring full screen viewing or using hardware acceleration.

Another aspect is how the scene is decomposed for downloading. BS Contact starts the loading of Inlines and other nodes with URL fields in the order the children of Group nodes are specified, walking into the deeper levels first. Inlines in currently not traversed parts (e.g. non-active children of a Switch/LOD node etc.) are loaded if needed. In Internet Explorer BS Contact starts the download of such in-active children if no other download activity is pending. For LOD nodes with direct Inline child nodes, BS Contact will display the lower LOD-Level if the Inline is not loaded yet. BspTree nodes are traversed by default in front to back order with respect to the viewer.
BS Contact currently does not unload nodes from memory. A script using node.addChildren /removeChildren Browser.createVrmlFromString could be used to perform scene memory management. A node is being deleted if no other reference exists to the node.

Specific to BS Contact vrmlscript/javascript interpreter speed

• minimize the number of eventOut's generated
• change an eventOut only if the value really changed (less redraw)
• Original

x = 0;
if (t>0.5)
x=t;
event = x;
• Better

x = 0;
if (t>0.5) {
x=event=t;
else if (x != 0) event = x;
• change an MF Event once at the end of the script and not individual elements in the body of a loop
• if applicable expensive calculations could be moved out of inner loops
• an initialize() script function can be used to set the startup state