Lighting Effects in Computer Games

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Lighting Effects in Computer Games
Stefan Felkel
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Talk Outline

• Importance of lighting
• Light Sources
• Lighting Model
• Material and OpenGL
• Shading
• Multipass Rendering
• Multitexturing
• Mapping Techniques
• Radiosity
• Examples and Screenshots

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Importance of Lighting
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Light Sources

• Directional Light

• Parameters color, intensity
• OpenGL up to 8 light sources

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Material

• Parameters
• Ambient (color)
• Diffuse (color)
• Specular (color)
• Shininess (specular exponent)
• Emissive (color)
• Color determined by these params params of
  light source lighting model

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Lighting Model (1)

• Good approximation to reality
• Illumination calculated with LM
• OpenGL LM
• Ambient Lighting
• Diffuse Lighting
• Specular Lighting
• Total lighting intensity

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Lighting Model

• Ambient Lighting

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Lighting Model

• Diffuse Lighting

• View light-vector no lighting gt 90

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Lighting Model

• Specular Lighting

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Shading

• Flat Shading

• Gouraud Shading

• Phong Shading

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Cube Environment Mapping
6 Textures ? 1 Cubemap
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Multipass Rendering

• Lighting calculations done in separate passes
• Each successive pass modifies the result of the
  pass before
• Quake III up to 10 passes
• Base textures
• Lightmaps
• Fog
• ...

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Multitexturing

• In a single pass, multiple textures are accessed
• Multiple stage model output of each stage
  becomes input for next
• Input for 1st stage is fragment color

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Light Mapping (1)

• Light maps low resolution precalculated
• Introduced by Quake

Lightmap Texture Combined Texture
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Light Mapping (2)
Multiple light maps packed into single texture
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Gloss Mapping

• Gloss map
• monochrome texture
• stores specular intensity values

?


Gloss maptexture
Diffuselighting
Specularlighting
Final combined result
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Radiosity

• Based on thermal heat transfer
• Viewpoint independent
• Radiosity radiance exiting from a patch
• Deals with area light sources
• Radiosity is used for light map calculation

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Radiosity
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Meshing the Environment

• Patch surface, area, texel (light maps)
• Every patch gets energy from surrounding patches

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Examples

• Wolfenstein 3D (1992)
• Doom (1993)
• GLQuake (1996)

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Wolfenstein 3D (1992)
Screenshot from Wolfenstein (full-bright)
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Doom I (1993)
Screenshot from Doom I (Depth Cueing)
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GLQuake (1996)
Screenshot from Quake II (Radiosity for light map
calculation)
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End

• Thanks for your attention!