Advances in Real-Time Vxel-Based GI Alexey Panteleev, Senir Develper Technlgy Engineer Rahul Sathe, Senir Develper Technlgy Engineer March 21, 2018 Bth #223 - Suth Hall www.nvidia.cm/gdc
Recap n VXGI Vxel Glbal Illuminatin Inspired by Sparse Vxel Octree Glbal Illuminatin (SVOGI) Clip-map used instead f ctree Fully dynamic scene supprt Vxelizing a game-like scene frm scratch takes nly a few ms Supprts multi-bunce GI thrugh a tempral feedback lp n irradiance 2
Crnell Bx Scene 3
VXGI Algrithm: Vxelizatin Opacity Emittance / Light 4
VXGI Algrithm: Tracing Diffuse Rugh Specular n Fine Specular n 5
Results f Cne Tracing Indirect Diffuse Indirect Specular 6
Final Result Direct Lighting Only Direct and Indirect 7
Vxel Ambient Occlusin VXAO Easier t cmpute than full glbal illuminatin N light prcessing, nly pacity Easier t integrate int engines N materials r lights during vxelizatin Lks better than screen-space techniques Wrld-space, nt screen-space Best if cmbined with small-scale SSAO 8
Area Lights with VXGI T bright T dark 9
Better Area Lights with VXGI 2.0 10
Vxel Area Lighting 11
Area Lighting A ht tpic f interest in the industry and academia 12
Area Lighting A ht tpic f interest in the industry and academia Linearly Transfrmed Csines A new technique invented in 2016 13
Area Lighting A ht tpic f interest in the industry and academia Linearly Transfrmed Csines A new technique invented in 2016 Impressive lighting fr area lights Cmplexity is O(n) n is # f edges https://eheitzresearch.wrdpress.cm/415-2/ 14
Area Lighting A ht tpic f interest in the industry and academia Linearly Transfrmed Csines A new technique invented in 2016 Impressive lighting fr area lights Cmplexity is O(n) n is # f edges But the cclusin is missing https://eheitzresearch.wrdpress.cm/415-2/ 15
Vxel Area Lighting VXAL 16
Vxel Area Lighting VXAL Distribute cnes ver the area light Area Light Diffuse Indirect 17
Vxel Area Lighting VXAL Distribute cnes ver the area light Occlusin Large Scale: Cne tracing similar t VXAO Small Scale: Screen space shadws 18
Vxel Area Lighting VXAL Distribute cnes ver the area light Occlusin Large Scale: Cne tracing similar t VXAO Small Scale: Screen space shadws Irradiance Diffuse and Specular Linearly Transfrmed Csines 19
Vxel Area Lighting VXAL Distribute cnes ver the area light Occlusin Large Scale: Cne tracing similar t VXAO Small Scale: Screen space shadws Irradiance Diffuse and Specular Linearly Transfrmed Csines Mdulate irradiance with cclusin 20
Vxel Area Lighting VXAL Distribute cnes ver the area light Occlusin Large Scale: Cne tracing similar t VXAO Small Scale: Screen space shadws Irradiance Diffuse and Specular Linearly Transfrmed Csines Mdulate irradiance with cclusin Apply material parameters like albed, cmpsite int the final view 21
Multiple area lights supprted Area Lights Rectangular in shape Textured r Slid clr Each light has sme rendering cst Dynamic textures are nt free Wide range f quality settings Tracing reslutin: half-res t quarter-res Occlusin quality: use mre r fewer cnes per unit angle Actual number f cnes is adaptive and varies per pixel 22
BRDF Linearly Transfrmed Csines Hw much light transfers frm incming directins t utging directins https://eheitzresearch.wrdpress.cm/415-2/ 23
BRDF Linearly Transfrmed Csines Shading: Hw much light transfers frm incming directins t utging directins Integrate BRDF ver the light s spherical prjectin https://eheitzresearch.wrdpress.cm/415-2/ 24
BRDF Linearly Transfrmed Csines Shading: Hw much light transfers frm incming directins t utging directins Integrate BRDF ver the light s spherical prjectin Analytic slutins exist, but nly fr simple BRDFs e.g. Phng, but very expensive https://eheitzresearch.wrdpress.cm/415-2/ 25
Linearly Transfrmed Csines Integrals invariant under linear transfrmatins Transfrm t the distributin Transfrm t the plygn Results are same https://eheitzresearch.wrdpress.cm/415-2/ 26
Linearly Transfrmed Csines Integrals invariant under linear transfrmatins Transfrm t the distributin Transfrm t the plygn Results are same Parameterized linear transfrms View Angle & Rughness Pre-cmputed and stred in textures https://eheitzresearch.wrdpress.cm/415-2/ 27
Linearly Transfrmed Csines Integrals invariant under linear transfrmatins Transfrm t the distributin Transfrm t the plygn Results are same Parameterized linear transfrms View Angle & Rughness Pre-cmputed and stred in textures Prefiltered textures fr textured lights https://eheitzresearch.wrdpress.cm/415-2/ 28
VXAL API Set the area lights Psitin, rientatin, size, clr, texture, etc. 29
VXAL API Set the area lights Psitin, rientatin, size, clr, texture, etc. Set the area lights tracing parameters Occlusin quality, screen-space shadws, tempral filtering, etc. 30
VXAL API Set the area lights Psitin, rientatin, size, clr, texture, etc. Set the area lights tracing parameters Occlusin quality, screen-space shadws, tempral filtering, etc. Set the view infrmatin Prjectin matrices, viewprts, etc. Prvide G-buffer channels 31
VXAL API Set the area lights Psitin, rientatin, size, clr, texture, etc. Set the area lights tracing parameters Occlusin quality, screen-space shadws, tempral filtering, etc. Set the view infrmatin Prjectin matrices, viewprts, etc. Returns Prvide G-buffer channels Diffuse Irradiance channel Specular Irradiance channel 32
Supprt ther types f area lights Maybe disk r line lights Imprve image quality Future Wrk Near-field cclusin Flickering in lw-res mdes 33
References Realtime plygnal-light shading with linearly transfrmed csines by Heitz, E., Dupuy, J., Hill, S., and Neubelt, D. 2016, Transactins n Graphics 35 34
VXAL DEMO 35
VXGI 2.0 New Features (besides VXAL) 36
One-Pass Vxelizatin VXGI 1.0: Separate vxelizatin passes fr pacity and emittance Twice the CPU cst, almst twice the GPU cst n tp f ther rendering passes VXGI 2.0: Can d everything in ne pass Or multiple, up t the applicatin Each pass adds sme pacity and emittance t the vxel vlume 37
Custm G-Buffer Layuts VXGI 1.0 requires a specific data layut and prjectin Hardware depth, linear nrmals, rughness in nrmal.w Planar prjectin nly VXGI 2.0 takes HLSL cde t lad gemetry inf fr a pixel Lens-Matched Shading Anything that reslves t a psitin and nrmal will d VRWrks MRS and LMS prjectins, r anything else Many tracing settings can vary per-pixel 38
View Reprjectin VXGI 1.0 supprts reusing lighting infrmatin frm the previus frame Tempral reprjectin r tempral filtering VXGI 2.0 adds reuse between views in the same frame Cmpute lighting fr the left eye Reprject matching surfaces t the right eye Fill the hles N limits n the number f views 39
Simultaneus VXGI, VXAO, and VXAL VXGI 1.0 had tw mdes AO mde: ambient cclusin channel is prduced GI mde: diffuse channel is prduced with ambient lighting added VXGI 2.0 changes hw the GI mde behaves Diffuse channel has AO in the alpha cmpnent Can cmpse as necessary n the applicatin side VXAL is independent Separate API Same behavir in GI and AO mdes 40
Other Imprvements 41
3D r 6D pacity replaced by scalar Simpler Vxel Frmats Same quality, better perfrmance Can d fractinal pacity materials nw Multiple emittance frmats replaced by single FLOAT16 With a functinal detur fr GPUs which d nt supprt FP16 atmics Occlusin-nly mde with n emittance can still be enabled 42
Simpler and Mre Flexible Materials Fewer cntrls frm the CPU side Mst f MaterialInf members remved Only Adaptive Material Sampling Rate is still there Mre pwerful n the shader side Fractinal pacity, variable per-vxel Tw-sided materials with different reflected clrs Adjusting plant pacity (animated) 43
Simpler Tracing Cntrls VXGI 1.0: numcnes, cneangle, nrmalgrupingfactr,...,... VXGI 2.0: quality, sftness, directinalsamplingrate,... Adjust Quality and Sftness t get an acceptable lk Then adjust the sampling rate and tempral filtering t get a usable nise level 44
There s Mre... Separate SSAO pass Supprt fr pre-view translatin Imprved upscaling and tempral filters Nn-cubic vxel vlumes Reduced light leaking Fine cntrl ver D3D extensins Imprved NVRHI 45
Summary 46
Summary New versin: VXGI 2.0 VXAL: High-quality area lighting with shadws Lts f smaller new features Better perfrmance than VXGI 1.0 Available sn Mid-April 2018 SDK and Unreal Engine 4 integratin 47
Thank yu! Questins? Cntact us: alpanteleev@nvidia.cm rsathe@nvidia.cm 48
Bth #223 - Suth Hall www.nvidia.cm/gdc