lighting: illusions of illuminationusers.monash.edu.au/~myless/graphicsig/animation/...sheets,...
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The Animation ProcessThe Animation Process
Lighting:Lighting:Illusions of IlluminationIllusions of Illumination
Lighting = realism
Although real people versus real clay/plastic Although real people versus real clay/plastic is up to texturesis up to textures
Realistic lighting = render timeRealistic lighting = render time
Some properties of lights
ColourColourBrightnessBrightnessShadow-castingShadow-castingVolumetricVolumetric
Types of lights : directional light
Also known as sun Also known as sun (light), infinite light(light), infinite lightParallel raysParallel raysSame lighting at any Same lighting at any point in the scenepoint in the scene
Types of lights : point light
Also known as bulb Also known as bulb light, omni light, local light, omni light, local light light Spherical volumeSpherical volumeFall-off is possible Fall-off is possible (distance)(distance)
Types of lights : spotlight
Also known as kliegAlso known as kliegRadius – limited areaRadius – limited areaFall-off is possible Fall-off is possible PenumbraPenumbraSoft shadows are Soft shadows are possible (can be possible (can be simulated with a simulated with a cluster of point lights)cluster of point lights)
A word about ambient light
Can be set for each Can be set for each object, or sometimes object, or sometimes can be set for entire can be set for entire scenesceneSimple 3D may use Simple 3D may use only ambient lightingonly ambient lightingCan be simulated Can be simulated with light at camera with light at camera positionposition
100% ambient lighting
Texture without lightingTexture without lightingUsually renders very Usually renders very fastfastUsed for games & VRUsed for games & VRDrawback : lack of Drawback : lack of shadows can look weirdshadows can look weirdWorkaround: use a Workaround: use a light-mapper, which light-mapper, which “bakes” lighting and “bakes” lighting and shadows into the shadows into the texture maptexture map
Traditional 3-point light setup
Main lightMain lightFill light (one or more)Fill light (one or more)Rim lightRim lightMay need to be set up for each camera angleMay need to be set up for each camera angle
Light example: “model” lighting
““Model light” = Model light” = Ambient lighting = Ambient lighting = light at cameralight at camera
Light example: main light only
Usually casts Usually casts shadowsshadowsSoft shadow edges Soft shadow edges will depend on main will depend on main light – spotlight, point light – spotlight, point light, directionallight, directional
Light example: added fill light
In real film or In real film or photography, use of photography, use of matte white boards, matte white boards, sheets, umbrellassheets, umbrellasSimilar to ambient Similar to ambient lightinglightingSimulates low-Simulates low-intensity reflection intensity reflection from other surfaces from other surfaces in the scenein the sceneOften no shadowsOften no shadows
Light example: added rim light
Makes a character Makes a character stand out from the stand out from the background, as 3Dbackground, as 3DCan be thought of as Can be thought of as a variation on a fill a variation on a fill lightlight
Light example: added feature light
Lights that only Lights that only interact with the interact with the eyes, to add sparkleeyes, to add sparkleObvious examples in Obvious examples in old black-and-white old black-and-white movies = light movies = light “masks”“masks”Shadows from the Shadows from the environment – environment – window frames, sun window frames, sun through leavesthrough leaves
Variations on the traditional setup
Use sun (directional) light as main lightUse sun (directional) light as main lightFill or rim lights only (film noir look, Fill or rim lights only (film noir look, moonlight)moonlight)Feature lights (eye glitter, eye emphasis)Feature lights (eye glitter, eye emphasis)Ambient plus one main light for simple Ambient plus one main light for simple lightinglighting
Special lighting setups
Instrument up-lighting for dramatic effectsInstrument up-lighting for dramatic effectsHeavenly down-lighting for “aura”Heavenly down-lighting for “aura”Uplighting: evil and/or instrument panelsUplighting: evil and/or instrument panelsBack-lighting for suspense and science fictionBack-lighting for suspense and science fiction““Film noir” minimal lighting, black & whiteFilm noir” minimal lighting, black & whiteOld-fashioned feature lightingOld-fashioned feature lighting““Lens flare” effectsLens flare” effectsGlowsGlowsVolumetric effectsVolumetric effectsImage-projecting lights (colour, stencil/mask)Image-projecting lights (colour, stencil/mask)
Standard lighting : raytracing
Trace rays through virtual monitor from every Trace rays through virtual monitor from every visible surface point back to every lightvisible surface point back to every lightSpotlights count as a cluster of multiple lightsSpotlights count as a cluster of multiple lights
High-tech lighting techniques
Some tecniques more modern than others, Some tecniques more modern than others, particularly in consumer-level softwareparticularly in consumer-level softwareThese lighting techniques often require more These lighting techniques often require more intensive calculations = longer rendering intensive calculations = longer rendering timestimesTrade-off : rendering time vs realismTrade-off : rendering time vs realismLarger studios have massive “render farms”, Larger studios have massive “render farms”, which can consist of hundreds of high-which can consist of hundreds of high-powered computers (often rack-mounted, powered computers (often rack-mounted, with a central control set-up) with a central control set-up)
High-tech lighting : radiosity
Divide surface into Divide surface into patches, energy patches, energy equationsequationsGood for architecture Good for architecture – light equations only – light equations only calculated oncecalculated onceButBut
No transparencyNo transparencyNo mirror reflectivityNo mirror reflectivity
[Sample images from POV-Ray][Sample images from POV-Ray]
High-tech lighting : global illuminationSuperset of raytracing Superset of raytracing and radiosity, attempts and radiosity, attempts to realistically model to realistically model lightinglightingVirtual photons fired Virtual photons fired from light sourcesfrom light sourcesAccumulative light Accumulative light effects, surfaceseffects, surfacesCapable of simulating Capable of simulating reflective and refractive reflective and refractive causticscaustics
[Sample images from POV-Ray][Sample images from POV-Ray]
High-tech lighting : hybrid renderers
Capable of more than one rendering Capable of more than one rendering technologytechnologyRadiosity for matte surfaces, raytracing for Radiosity for matte surfaces, raytracing for relective surfaces, photons for transparent relective surfaces, photons for transparent and refractive surfacesand refractive surfaces
High-tech lighting : area lights
Area lightsArea lightsLight arraysLight arraysGridsGridsDomesDomesSimulate fluorescent lighting, light from Simulate fluorescent lighting, light from ceilings, light from all areas of skyceilings, light from all areas of sky
High-tech lighting : Image-based lighting
An extension of An extension of radiosity, using pixels radiosity, using pixels as luminous patchesas luminous patchesHDRI - High Dynamic HDRI - High Dynamic Range ImagingRange ImagingFloating point colour Floating point colour channels - much more channels - much more than 256 values, than 256 values, including subtle detail including subtle detail in overlit and underlit in overlit and underlit areas.areas.
2D lighting : highlights
As geometryAs geometry
As overlayAs overlay
As effectsAs effectsSparkleSparkleLens flareLens flare
2D lighting : shadows
Shading applied to Shading applied to individual objectsindividual objects
As an effectAs an effectAs geometryAs geometry
Shading applied as Shading applied as an object in blending an object in blending mode (like a 3D mode (like a 3D stencil light)stencil light)Light as “white Light as “white shadow”, blendingshadow”, blending