Real- -time time global global illumination illumination in in - - PowerPoint PPT Presentation

Real Real-

• time

time global global illumination illumination in in interactive interactive applications applications and and games games

László László Szirmay Szirmay-

• Kalos

Kalos

Motto Motto

In theory, there is no difference In theory, there is no difference between theory and practice. between theory and practice. In practice, there is. In practice, there is.

Global Global I llumination I llumination rendering rendering

pixel

• 1. Visibility determination
• 2. Illumination computation
• New visibility and

Illumination tasks

Pure Pure Local Local I llumination I llumination

pixel

• 1. Color computation uses just

local information

• 2. Visibility only from the camera
• 3. Object order is free

GPU hardware GPU hardware achitecture achitecture

Interface Transform+ Illumination Clipping + Viewport transf. + Rasterization + interpolation Texturing Compositing (Z-buffer, transparency) Texture memory vertices triangles fragments Geometry Shader Vertex Shader Fragment Shader

Keys Keys to to GPUGI GPUGI

• Importance, reuse, and pre

Importance, reuse, and pre-

• computation

computation

• Simplification

Simplification

• Exploit the GPU

Exploit the GPU

– – Multipass

Multipass rendering rendering

• Results

Results of

• f a

a previous previous pass pass can can only

• nly be

be used used

– – Render

Render-

• to

to-

• texture

texture

• Results

Results of

• f one
• ne pass

pass can can be be used used by by another another pass pass

– – Floating

Floating point point textures textures

• HDR

HDR radiance radiance and and geometric geometric data data in in texture texture memory memory

Simplified GI Simplified GI

Large, Static environment Small, Dynamic

• bjects

Participating media Precompution-aided GI Shadow, caustics Simplified GI Localized Environment maps Shadow, caustics Simpflied GI Approximated multiple scattering Artifact free composition Environment maps

Beyond local Beyond local illumination illumination

Local illumination Variance Shadow maps Localized Environment maps Localized Diffuse/glossy irradiance maps Obscurances, ambient occlusion, Photon map, light cube map Light path maps

Map, Texture

Text Textrure rure atlas atlas = = unfolding unfolding

u v x y z

• 1. Pre
• 1. Pre-
• computation aided

computation aided methods methods

• Obscurances

Obscurances, ambient occlusion , ambient occlusion

• Light maps

Light maps

• Light path maps

Light path maps

Fake methods ( Fake methods ( obscurances

• bscurances,

, ambient occlusion) ambient occlusion)

Good for macrostructure and mesostructure

Light maps Light maps ∫Ω Lin(x,ω’) f(x)cosθ’dω’ =

f(x) ∫Ω Lin(x,ω’) cosθ’dω’ =L(x)

Irradiance

Allowing dynamic lighting Allowing dynamic lighting

Entry point Exit point

Preprocessing Preprocessing: : Exit Exit points points

• 1. Entry points:

random

• 2. Exit points:

correspond to texel centers

Preprocessing Preprocessing: : Transfer Transfer from from entry entry to to exit exit points points

entry point with unit irradiance

Preprocessing Preprocessing: : Reference Reference point point illumination illumination

Virtual lights unit irrad

Entry point 1 Entry point 2 Compression: PCA

Having the transfer factors Having the transfer factors

Results Results: : Room Room with with stairs stairs

16K entries 32 clusters 4Mb per obj 50 FPS

• 2. Environment map
• 2. Environment map

based techniques based techniques

• Specular

Specular reflections and refractions reflections and refractions

• Diffuse/glossy indirect illumination

Diffuse/glossy indirect illumination

• Global/localized approaches

Global/localized approaches

Environment Environment mapping mapping

Problems Problems of

• f environment

environment map map based based reflections reflections

Environment map Reference

distance color

Localization: distance map Localization: distance map

Ray tracing of distance maps Ray tracing of distance maps

Comparison Comparison of

• f

Localized Localized Refrections Refrections

Multiple Multiple interreflections interreflections

• So far we decomposed the scene to the

So far we decomposed the scene to the reflector and to the “rest” reflector and to the “rest”

• If all reflectors have their own distance

If all reflectors have their own distance map, it is correct. map, it is correct.

Frame 1 Frame 2

With multiple distance maps With multiple distance maps

Caustics Caustics-

• Causticus

Causticus-

• Kaustikos

Kaustikos

Caustic path generation Caustic path generation

Caustics Caustics

distance

point location power

32 x 32

Texture Texture modulation modulation

Texture uv of photon positions Vertex shader Billboard positions filter Pixel shader Lit texture or Light map

256 x 256

Quads or points with dummy pos

Summation with Summation with alpha blending alpha blending

Results (triangle) Results (triangle)

Results Results (billboards) (billboards)

Application Application: : Ray Ray-

• tracing

tracing effects effects in in games games

Diffuse/ glossy reflection Diffuse/ glossy reflection

cosθ’ L(x, ωo) = ∫Ω Lin(y,ωi) f(ωi,x,ωo) cosθ’ dωi x

Diffuse Diffuse/ / Glossy Glossy reflections reflections

cosθ’

∫Ω Lin(o,ωi) cosθ’ dωi

• No

self-occlusions!

Localized diffuse/ Localized diffuse/ glossy maps glossy maps

distance radiance

• 3. Participating media
• 3. Participating media

billboards

( )

ω α α ω ω r r r

j j j j

E C j I j L + ⋅ + − ⋅ = ) 1 ( ) , ( ) , (

Incoming radiance In-scattering term transparency Outgoing radiance Emission

Particles Participating medium

I lluminating participating I lluminating participating media: media: inscattering inscattering term term

sky color billboard slice 1 slice 2 slice 3 light source light pass final gathering pass

Particles Dust: 16 Fire: 135 Smoke: 112 FPS Spherical: 70 Planar: 80

Explosions Explosions

Shaded smoke Shaded smoke