ALS technical notes

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Revision as of 07:02, 17 October 2014 by Thorsten (talk | contribs) (Created page with "== Quality level mapping == The rendering quality of ALS effects is controlled by two main sliders, landmass effects and transition effects. Transition effects regulate overl...")
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Quality level mapping

The rendering quality of ALS effects is controlled by two main sliders, landmass effects and transition effects. Transition effects regulate overlay texturing quality whereas landmass effects regulate all other aspects of procedural texturing like pixel color postprocessing (dust, snow or wet terrain effects) and apparent terrain roughness (bump and parallax mapping).

In addition, specific effects for certain terrain types (water, urban, forest, agriculture...) and models in the scene can be switched on separately. In some cases this may be needed for a consistent visual impression: If a dust effect is used on the terrain, water needs to be rendered using a separate water shader, otherwise it will appear dusty as well. Likewise, if the Rayleigh haze is used in the highest quality terrain effect, then the highest quality water effect needs to be used to see the same Rayleigh scattering effect on the water.

For technical reasons (landmass and transition control the same shader code) the settings are sometimes mutually dependent, i.e. transition quality level 6 won't have any effect unless landmass quality is also level 6.

Transition

The mapping of quality to visuals of the transition slider is

1:

  • base texture scheme

2:

  • alternative hires airport keep effect

3:

  • base and overlay texture, runway effect (if landmass > 4)
  • supports secondary lights on runway and airport keep

4:

  • base, overlay and hires texture

6:

  • base, overlay, hires, detail, grain, dot and rock texture (if landmass > 6)

Landmass

(Quality levels 1 and 2 are reserved to represent fixed pipeline rendering and the classic FG default renderer in an eventually merged rendering GUI, currently however ALS is switched on per checkbox and not by quality level, so they do not have a function).

3:

  • ALS-rendered position-differential haze and light

4:

  • procedural snow cover on terrain
  • procedural dust and vegetation effects
  • wet terrain effect with approximate reflection half vector
  • patchy fog distribution

5:

  • noise bump-mapping and parallax mapping of terrain

6: (requires transition 6 as well)

  • wet terrain effect with correct reflection half vector
  • hires bump mapping and snow patchiness
  • variable upper haze layer surface
  • Rayleigh haze
  • secondary lights on all terrain types
  • slope line and strata effects