Fog

Introduction

Nazi Zombies: Portable uses it’s own 5-parameter, linear fog system. This was originally conceived this way as the PlayStation Portable’s hardware fog is linear and not exponential as is traditional for Quake and OpenGL itself. The Nintendo 3DS also adheres to this standard thanks to picaGL’s linear LUT fog. Other platforms manipulate these fog values to approximate them into standard exp2 fog modes. Exponential fog is significantly less granular and as a result this approximation will never be spot-on.

Parameters

usage:
    fog (start) (end) (red) (green) (blue)

Excerpt from fog command in the console.

When defining fog, you can provide a start and end distance, in units, of the fog “wall” that appears. The distance between start and end will impact intensity, and of course, the farther away start is from zero, the more visibility you have before the fog begins.

You can change the color of the fog given individual red, green, and blue color values. These values range from 0-100, with 100 being maximum intensity. Both pure black fog with 0 0 0 and pure white fog with 100 100 100 are supported.

As an example, below is the fog output for Nacht der Untoten:

current values:
    "start" is "240"
    "end" is "1550"
    "red" is "54"
    "green" is "55"
    "blue" is "59"

Translation

Linear to Exponential

Platforms that do not support linear fog will algorithmically approximate a decent exponential fog density to use instead. The formula is as follows:

fog_density_gl = ((fog_start / fog_end)/3.5f)

Exponential to Linear

FTE will still fallback to old exp2 fog behaviors if provided them, however all other platforms will ignore fog if any of it’s provided values are less than zero. This is intended behavior.