System Vegetation (Content Creation)

Opensimulator: Content Creators: Models: System Vegetation

System vegetation is a special form of models intended to create plants with a lower streaming cost than those made from prims, sculpts or mesh. The nodels are generated by the viewer, mostly from predefined values and data stored in two xml files that are included in the viewer downlaod package. Only a few parameters are delivered from the server. This of course means that the load the plants put on the servers is all but negligible. This is however not quite true for the viewer. System vegetation is always farily simplistic and not likely any serious stress to any modern client computer. But even so, neither the code nor the mesh generated are well optimized.

The main problem with system vegetation, however, is that it's way outdated. It was developed as early as 2002 and apart from the addition of one more ground coverage option it has never been updated. A lot has changed to computer graphics since then and although system vegetation isn't completely irrelevant most of the variants do not meet the expectations to visual quality people tend to have today.

Level of Detail

The LOD handling is not documented but trees (actual trees that is) have significant LOD reduction for their trunks whilst the branches/canopies don't seem to have any LOD reduction at all. Other plants do not seem to have any LOD simplification.

Physics

System vegetation is always phantom.

Variants

There are two basic kinds of system vegetation "Trees" (really any single plants) and "Grass" (really any multi plant ground cover)

Trees

A system tree is a single plant and there are 21 variants. Most of the names are self-explanatory:

• Pine 1
• Oak - This is not actually an oak at all but a small maple with orange autumn leaves
• Tropical Bush 1 - Looks like some sort of palm shrub
• Palm 1
• Dogwood
• Tropical Bush 2
• Palm 2
• Cypress 1 - Not really a cypress. The texture used for the foliage is from a cypress but the canopy shape is typical for genereic hardwood trees and not like any common type of cypress.
• Cypress 2 - Not really a cypress. The texture used for the foliage is from a cypress but the canopy shape is typical for genereic hardwood trees and not like any common type of cypress.
• Pine 2
• Plumeria - A seriously oversized flowering shrub.
• Winter Pine 1
• Winter Aspen
• Winter Pine 2
• Eucalyptus
• Fern
• Eelgrass
• Sea Sword
• Kelp 1
• Beach Grass 1
• Kelp 2

Grass

A piece of system grass consists of 32 flat panels with a picture of some sort of vegetation on them. The panels will always be aligned with the system terrain and can not be moved vertically. Nor can the panels be resized, changing the vertical (z axis) size has no effect. Changing the horizontal (x and y axis) size will change the distance between the panels.

There are six (really only five) system grass variants:

• Grass 0 - Yellowish-green grass with straws.
• Grass 1 - Dense cluster of poorly masked grass.
• Grass 2 - For most practiucal pruposes identical to Grass 0. It uses the same texture but is slightly bigger.
• Grass 3 - Similar to Grass 1 but lighter color and bigger.
• Grass 4 - An "autumn variant" of Grass 0/Grass 2. Bigger and with reddish-brown colors
• undergrowth_1 - Small alder(?) shrubs

Parameters

The parameters delivered by the server are type, location, scale and rotation.

The parameters stored in the XML files are

• for trees:
  • tree name
  • species
  • texture_id
  • droop
  • twist
  • branches
  • depth
  • scale_step
  • trunk_depth
  • branch_length
  • trunk_length
  • leaf_scale
  • billboard_scale
  • billboard_ratio
  • trunk_aspect
  • branch_aspect
  • leaf_rotate
  • noise_mag
  • noise_scale
  • taper
  • repeat_z
• for grass:
  • name
  • species_id
  • texture_id
  • blade_size_x
  • blade_size_y

All other parameters are predefined and can not be altered.

Creating System Vegetation

Technically it's very easy to create new system vegetation variants although since there is no documentation it make take a bit of trial and error, especially to figure out the UV mapping for the trees.

This is not recommended, however, since any new variants will have to be added to the XML files for the viewers of everybody who are supposed to see them. If a viewer comes across a variant it doesn't recognise, it will render it as a Pine 1 for trees or Grass 0 for grass.