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Give it some wings.

Introduction

This article describes how to generate environment maps that can be used as alternative reflection maps. For cars, you often just want the $trackenvmap texture (see shaders) since that is updated with the car as the center.

However, for track objects, such as buildings with window panes, you will want to avoid the $trackenvmap since that often contains visuals close to the car. For example, the road, kerbs and such. You don't want these to reflect in track objects, but rather create your own.

Custom reflection maps require Racer v0.8.40+.

Steps to use a custom-generated track environment map

The nicest maps are generated in the actual track itself, not trying to create envmaps in an editor such as Photoshop. Here are the steps to grab an environment map from within Racer:

Initial assumptions

• Live track mapping is turned on (in racer.ini, envmap.live_track=1, envmap.live_track.bits=16). envmap.live_track.render_once may be 1 (often used to avoid live environment maps taking up a lot of render time)

Render a reflection map

• Run a race on the track of choice.
• Move towards the position where you'd want to grab the environment map. Drive the car first, then move the camera to the spot of choice. For trackmap saving, the CAMERA position will be used, not the CAR position (!).
• Enter the console command 'trackmap save'. The images are now stored in data/dump/track_*.tga. There are 6 images; track_lt.tga, track_rt.tga, track_up.tga, track_dn.tga, track_fw.tga and track_bw.tga. These stand for left, right, up, down, forward and backward. Note that the directions are relative to the world, not the car.

Using a reflection map in your shader definitions

• You now have 6 images that make up a cube. For example, we want a glass shader in our track which uses the generated images. Rename the track*.tga to glass*.tga (any name is possible, as long as the postfixes _lt, _rt etc are preserved). A quick way to do this is to use the command prompt (start 'cmd') and use these commands: 'cd \sims\racer\data\dump', 'ren track*.tga glass*.tga'. Mouse users can just use the explorer and rename the files one by one. ;-)
• Optionally, you can modify the image files (in Photoshop for example) and blur them somewhat to make them a little nicer for a softer reflective look.
• Move the 6 images to your track directory (i.e. data/tracks/mytrack/glass*.tga).
• Modify the shader of your glass to use the cubemap images (an example is shown below). For glass_lt.tga etc, use map=glass*.tga. Only TGA files are currently supported! (v0.8.40)
• Load up the track, load track.shd in your text editor, and tune the 'reflect=...' line until it looks ok. You can go above 1.0 in this case, since the original TGA's are downconverted (tonemapped) from 16-bits to 8-bits using a software tonemapper. TGA can only go upto 8 bits per channel.

The shader (in track.shd) can look as follows (the vf_reflect_window tree is just a template that is referenced by the actual shader, shader_glass):

vf_reflect_window
{
  vertex_shader
  {
    file=dyn_standard_reflect_window_v.cg
  }
  fragment_shader
  {
    file=dyn_standard_reflect_window_f.cg
  }
}
...
shader_glass~vf_reflect_window
{
  reflect=50.0
  diffuse=1 1 1
  ambient=0.8 0.8 0.8
  specular=0.1 0.1 0.1
  cull=none
  layer0
  {
    map=glass.tga
  }
  layer1
  {
    map=glass*.tga
  }
}

On 8 bits vs 16 bits

The nicest quality for an envmap would be 16-bits, giving a higher dynamic range. The pros for 8 bits are that it uses generic .tga files, so you can modify the TGA files after generating them. For example, you can use Photoshop to blur them a bit for softer reflections.

(last updated November 13, 2012 )