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Go for the GT5 look using vertex and fragment shaders!

Introduction

Racer cars can have a couple of lights defined. In-game you can press 'L' (although this is definable in data/controls/default.ini, search for 'key=l') to toggle the player's car lights on and off.

Two types of lights exist; 3D models and projected lights. The first ones are just models that are turned on or off based on the light state. The 2nd one is defined deeper in the rendering engine as a separate pass to add light to rendered objects in front of the car. It does so by projecting a texture in perspective while re-rendering the objects (lookup the internet on 'projected textures' for hardcore info).

Lights are defined in a car's car.ini file. Tracks can be defined as night tracks by setting special.ini's gfx.night to 1. In that case, all car lights will be on by default when loaded.

3D light models

Light models; braking lights (that are drawn when the player is braking) are specified in body.model_braking_l and body.model_braking_r, while body.model_light_l and body.model_light_r specifies front lights models.

Animated light models

Since v0.6.5, there is a small animation feature for lights, specifically meant for F1 flashing lights for example. The setting is in car.ini's animation.flash_lights. This setting specifies (in milliseconds) the duration of the 'on' state of the lights. The 'off' state is currently equally long.

Projected lights

You specify projected lights in the car.ini's lights.light<n>.texture fields. See data/cars/default/car.ini for an example (which comments out the texture used). An example texture and screenshot follows below. Currently no positioning is possible yet (10-11-08), this should be added soon. Currently only 1 (front) projected light is supported.

Further options (definable per car since v0.6.5+):

Example light texture (note that this texture was vertically flipped at 20-1-2009 at the time of Racer v0.7.2; this is a more logical orientation for projected images):

Potential problems with projected lights

Projected lights redraw part of the scene, lightening the pixels. Although this doesn't take into account any real lighting effects (diffuse colors may look more washed out than they should), it is a cheap method. It is important to realize how the projection works:

• All objects close to the light are redrawn, using 2 Cg shaders: data/renderer/shaders/projected_texture_v.cg and data/renderer/shaders/projected_texture_f.cg.
• The redrawn polygons are Z-tested (the depth buffer). This may give trouble with subtle line overlays on roads for example. If you're drawing polygons with white lines on top of a road for example (decals), make sure you don't write the depth buffer (in track.shd, set the shader's depthwrite property to 0). Perhaps using 'alphafunc' this effect is reduced, but it's better to avoid writing the Z-buffer at all (which is cheaper in terms of framerate).

Example screenshot:

Flares

You can add flares to the car to intensify the lights. The flares light up when the viewing direction starts to match the direction of the flare. Racer v0.8.22 and on uses the klux lighting model so the coloring can now be much higher (instead of values between 0 and 1, you now uses a value between 0 and around 100).

Further options (definable per car since v0.6.5+):

To understand billboarding better; there are multiple ways to do billboarding. For flares there are 2, screen aligned (billboard=0) and normal aligned (billboard=1). The first type looks like this (the alpha was removed here to clarify the billboarding):

Notice how the regular brake lights are ok, but the 3rd (wide) brakelight doesn't cover the brakelight nicely. So use billboard=1 for that flare, and you get the better looking result (note the side brakelights still use billboard=0 here):

An example extract from a car.ini file:

flares
{
...
  flare3
  {
    pos=0.65 0.35 -1.7
    normal=-0.05 0 -0.5
    color=40 10 10
    size_factor=0.5
    billboard=1
  }
}

Remember the car's coordinate system to be able to define flare normals correctly:

(last updated November 13, 2012 )