Darkplaces lighting

Revision as of 15:29, 27 July 2012

Template:Article unfinished Darkplaces engine uses combined lighting model. Several lighting methods are implemented to give best results at cases they are aimed for.

Light methods and effects

There is 4 lighting methods used in Darkplaces:

• Vertex lighting - low frequency static lighting, aimed at big counts of simple surfaces
• Lightmaps - high frequency static lighting, aimed at surfaces that receives shadows from static objects
• Lightgrid - low frequency static lighting, aimed at moving entities
• Realtime lighting - fully dynamic lighting (each light is a separate pass), aimed at switchable and moving lightsources that lights moving entities

Additionaly, Darkplaces supports a number of lighting effects:

• Coronas - aimed to simulate glow around lights, which looks good on small and medium size lights
• Planar shadows - not a lighting but shadowing method where each entity cast one shadow on the floor
• Customized modellight - lightgrid-sampled model lighting could be replaced in realtime
• Fog - global fog and global volumeric fog (with height set) are suppored

Light models

Darkplaces using several lighting models, most of them are set globally:

• Phong lighting model - generic lighting model used on all methods
• Fake light - a developer-only mode which is forced on non-lit maps (ones which was compiled by didnt get LIGHT phase). This is infinite realtime light that is cast from eye position.
• Toon shading - a phons lighting model with altered shading.
• Fullbright - no lighting applied

Shadow mapping vs Stencil shadows

Stencil shadow volumes is a shadow rendering method Darkplaces used in pre-2010. Since 2010 shadow mapping was implemented by Eihrul. Shadowmapping have a number of advantages over shadow volumes and is considered to replace them:

• It is faster to render (especially on complex area maps)
• Takes less CPU time (as construction of shadow volumes is not required)
• Supports LOD (far lights rendered with lower shadowmap resolution)
• Shadow edges are not ideally sharp

Comparison of different lighting methods

Console variables

 r_shadow_realtime_world : Enabled realtime lighting of world lights (stored in external .rtlights file)

 r_shadow_realtime_dlight : Enabled realtime lighting of dynamic lights (created by entities)

 r_shadow_* : A group of cvars to control realtime lighting

 r_shadow_shadowmapping : Enables shadowmapping which replaces default shadow volume-based lighting

 r_shadow_shadowmapping_* : A group of cvars to control shadowmapping

 r_shadows_* : A group of cvars to control planar shadows

 r_showlighting : Show areas lit by dynamic lightsources. Useful for finding out why some areas of the map render slowly (bright orange = lots of passes, slow)

 r_showshadows : Show areas covered by shadow volumes. Useful for finding out why some areas of the map render slowly (bright blue = lots of passes, slow). Only matters if using shadow volumes.

See also

• Per-pixel lighting