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 SourcesDirectional Light

Point Light

Spot 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 >= 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 texturesLightmapsFog ...

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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)

+ =

Lightmap + Texture = Combined Texture

Light maps: low resolution & precalculated Introduced by Quake

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Light Mapping (2)

Multiple light maps packed into single

texture

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Gloss Mapping

+ =

Specularlighting

Gloss maptexture

Diffuselighting Final combined

result

Gloss map: monochrome texture stores specular intensity values

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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)

EndThanks for your attention!