OCCL

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OCCL (IPL section)
Short description:Creates occlusion culling zones
Supported games:Vice City San Andreas GTA IV
IPL Sections:
2DFX AUZO BLOK CARS CULL ENEX GRGE
INST JUMP LINK LODM MLO+ MULT OCCL
PATH PICK RTFX SLOW TCYC VNOD ZONE

OCCL is a section in the item placement file in Vice City, San Andreas, and GTA IV. It is used to create occlusion culling zones that helps make the game run smoother in certain parts of the world. Since it is wasteful to render models behind opaque models, these zones can disable the rendering of any models that are directly behind the zones.

Format

Vice City

A map of Vice City's occlu.ipl areas
occl
MidX, MidY, BottomZ, WidthX, WidthY, Height, Rotation
end

The section is used in the occlu.ipl file but it can be used in any IPL files.

Vice City Identifier Type Description
A,B MidX, MidY float[2] The X and Y coordinates of the center of the occlusion zone.
C BottomZ float The bottom Z coordinate of the occlusion zone.
D,E WidthX, WidthY float[2] The width of the occlusion zone in units.
F Height float The height of the zone — the difference between the top and the bottom of the zone.
G Rotation float The rotation of the occlusion zone in degrees.

San Andreas

The section is used in occluint.ipl, occluLA.ipl, occlusf.ipl, and occluveg.ipl files.

occl
MidX, MidY, BottomZ, WidthX, WidthY, Height, Rotation, , ,
end
San Andreas Identifier Type Description
A,B MidX, MidY float[2] The X and Y coordinates of the center of the occlusion zone.
C BottomZ float The bottom Z coordinate of the occlusion zone.
D,E WidthX, WidthY float[2] The width of the occlusion zone in units.
F Height float The height of the zone — the difference between the top and the bottom of the zone.
G Rotation float The rotation of the occlusion zone in degrees.
H,I float
J int

Issues

When removing buildings from the world, you may see unexpected pop ups caused by existing occlusion zones. Deleting all the occlusion zones is the easiest solution. An example of this issue is the Liberty City project. Before this section was researched, the team experienced unexpected pop ups with models loading and unloading behind areas where Vice City's buildings used to be. Someone realized that the occlu.ipl was the problem and deleted every line in that file. The pop ups disappeared and the issue was resolved.

Statistics

Total number of OCCL entries in:

Vice City: 344 (max 350)

Tools and scripts