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"The true sign of intelligence is not knowledge but imagination." - Albert Einstein

Introduction

This document describes how rain works in Racer. The current text is based on rain in v0.6.5-v0.8.9.

The files involved

The following files play a part in rain:

• data/audio/rain*.wav - rain samples
• data/audio/thunder*.wav - thunder samples
• data/images/spray.tga - rain spray image
• racer.ini - general settings
• data/tracks/<trackname>/special.ini - track specific settings

Turning rain on

Rain state is decided per track. As the mood of a track changes when it's rainy, textures can be made less bright, the sun color reduced a bit (see a track's special.ini). In the special.ini, set env.rain to something between 0 and 1, where 0 is no rain, 1 is full rain. To enable rain on a track follow these steps:

• Add the following (or make sure it's there) to your track's special.ini file:
  env
  {
  ; Environment
  rain=0.7
  thunder=0.3
  }
  The 0.7 indicates 70% rain. The 'thunder' line indicates whether thunderstorms are active. 0 means no thunderstorm, 1 means full thunderstorm.
  

Turning the sun off

Some rainy tracks may look strange with a large bright sun. In the track's special.ini file, you may turn off the sun by settings gfx.sun.enable to 0 (v0.6.5+).

Tuning rain

The following can be tweaked:

• Modify the intensity of the projected shadows of car. This parameter is set in data/tracks/<track>/special.ini and is in gfx.shadows.intensity_projected. 0 means fully transparent (invisible) and 1.0 means fully opaque.
• Modify the spray image (data/images/spray.tga)
• Modify the spray intensity by tweaking the values of fx.interval in racer.ini; a good value would be 8, although it generates quite a lot of particles.
• Modify the loss of grip on surface (globally for each track) in racer.ini under environment.rain.grip_factor. A value of 0 would mean no grip at all if the track's rain factor is set at 1, 1.0 is full grip. The extract below sets the grip loss to 60% for a full-rain track. Note that this global is multiplied with the track's rain factor. So if this factor is 0.5, and the track's env.rain setting is 0.5 as well, you only get 0.5*0.5 = 0.25 grip loss (25%).


   environment
   {
     ...
     rain
     {
       ; Multiply grip of surfaces for full rain (=1.0)
       grip_factor=0.6
     }
   }
  

Dynamic rain (over time)

The rain amount can be varied a bit over time. Note that a full cycle between sunny and rain is not really possible; rain tracks preferably have specific shaders defined to make the track look wet, and Racer doesn't support fully dynamic weather where the track can dry up.

In a track's special.ini file, you can specify a rain curve (see Curved on how to create curves). An example extract from special.ini and rain.crv file is shown below:

env
{
  rain_curve=rain.crv
}

The rain.crv file opened in Curved. Note the maximum vertically (rain amount) is 1.0 and the maximum horizontally (time in seconds) is 20. Every 20 seconds this curve will loop.

(last updated November 13, 2012 )