High Quality Direct3D 10.0 & 10.1 Accelerated Techniques. Jon Story, AMD Holger Gruen, AMD

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2 High Qualit Direct3D 0.0 & 0. Accelerated Techniques Jon Stor, AMD Holger Gruen, AMD

3 Agenda» High Definition Ambient Occlusion» High Qualit Shado Filtering

4 High Definition Ambient Occlusion (HDAO)

5 Conentional AO :» Compute Offset Transform Eecuted to a camera as to group a post-perspectie fullscreen of space 3D positions from arranged space processing screen and in test passa XY sphere against and depth depth» Occlusion Factor ~= Failure Rate Occlusion = /2 3/4

6 Conentional AO : 2» Usuall requires man depth samples to achiee acceptable results» Maths oerhead per sample is high Transform to post-perspectie space Depth testing Result attenuation» Filtering pass almost essential to smooth out dithering and banding artifacts

7 The Aim of HDAO» Delier a belieable AO loo» Achiee affordable performance on toda s HW» Aoid need for filtering pass(es) Keep performance higher No additional render targets required» Eas to incorporate No normals required Account for normals ith ease if aailable

8 Ho does HDAO Fit into the Rendering Pipeline?» Render Use Finall depth combine scene (and as normals) AO usual buffer as ith» Optionall input(s) original scene to render AO shader normals as part of an MRT setup

9 Ho does HDAO Wor?» If Still Sample Also both a detects fullscreen tins the a central occlusion fall pair post ithin of piel processing piels, beteen a of specified interest radius, mirrored pass and objects record and that through its are camera closer the central to Z alue each the piel,» camera and Detects otherecord than alles their in camera central camera piel, z Z alues space then» e Not hae _onl_ detected creases a alle Valle = false Valle = true

10 Valle Detection» The Start Perform simplest b a sampling alle implementation test the for central each tin ould depth pair of piel, be (mirrored) a 33 and conerting samples pattern to» camera Valle test Z produces binar result Credit Occlusion to Holger Factor Gruen = Valle for this Test idea

11 Ho does Gather Wor?» Gather Similar to fetches Fetch4 4 point eposed sampled on DX9 teels ATI GPUs in a single instruction» Aailable There are on non all Direct3D issues in 0. preious & hardare ersions of the HLSL compiler» Used Must use on single March channel 2009 SDK formats later (restriction gone for DX) depth buffer Shado maps f4depth = DepthTe.Gather( SamPoint, f2coord ); ( 0, 0 ) (, 0 ) W Z X Y ( 0, ) (, )

12 Direct3D 0.0 Version of Gather» Be sure to get the integer offsets correct for the 4 samples // Direct3D 0. f4ret = Te.Gather( g_samplepoint, f2tecoord ); // Direct3D 0.0 f4ret. = Te.SampleLeel( g_samplepoint, f2tecoord, 0, int2( 0, ) ).; f4ret. = Te.SampleLeel( g_samplepoint, f2tecoord, 0, int2(, ) ).; f4ret.z = Te.SampleLeel( g_samplepoint, f2tecoord, 0, int2(, 0 ) ).; f4ret. = Te.SampleLeel( g_samplepoint, f2tecoord, 0, int2( 0, 0 ) ).;

13 Gather Pattern» It ould be ideal to accelerate depth sampling using Gather W X Y Z W X Y Z W X Y Z W X Y Z» Each Gather should tessellate around center piel» Each Gather needs to hae a mirrored tin» Simpl add additional rings of Gathers W X Y Z W X Y Z W X Y Z W X Y Z W X Y Z W X Y Z W X Y Z W X Y Z» To perfectl mirror samples, onl requires a sizzle z ith z

14 Natural Vectorization for( igather=0; igather<num_gathers; igather ) { } // Gather mirrored tin depth samples (and conert to camera Z) f4sampledz[0] = DepthTe.Gather( SamPoint, f2tecoord ); f4sampledz[0] = -g_fqtimesznear / (f4sampledz[0] - g_fq ); f4sampledz[] = DepthTe.Gather( SamPoint, f2mirrortecoord ); f4sampledz[] = -g_fqtimesznear / (f4sampledz[] - g_fq ); // Detect alles // First tin f4diff = fcenterz. - f4sampledz[0]; f4compare[0] = ( f4diff < g_fhdaorejectradius. )? (.0f ) : ( 0.0f ); f4compare[0] *= ( f4diff > g_fhdaoacceptradius. )? (.0f ) : ( 0.0f ); // Mirrored tin f4diff = fcenterz. - f4sampledz[]; f4compare[] = ( f4diff < g_fhdaorejectradius. )? (.0f ) : ( 0.0f ); f4compare[] *= ( f4diff > g_fhdaoacceptradius. )? (.0f ) : ( 0.0f ); // Accumulate occlusion factor We perform the alle detection logic on 4 alles at once We Gather 4 samples at We efficientl once Finall e eight conert and store 4 depth the occlusion samples to factor camera of 4 alles space at a time f4occlusion.z = ( g_f4ringweight[igather].z * f4compare[0].z * f4compare[].z );

15 HDAO On Off Buffer (depth (depth onl) onl) 40 Gathers No filtering needed HDAO Code Sample

16 Bringing in Camera Space Normals» HDAO easil accounts for normals» Scale Z component of camera space normal b desired amount» Add scaled normal to camera Z alue» Run alle detection code as before // Offset b scaled normal f4cameraz = ( f4normalz * g_fnormalscale );

17 HDAO On Buffer (depth (depth & onl) normals) & - 80 Gathers (could use alot less) - No filtering needed

18 Earl Rejection Test» Lo For smooth densit normals, meshes can compute produce undesireable angle beteen occlusion them» Or Terrain compute direction ectors from S dome full camera space positions» Calculate Dramaticall the increase angle of performance the alle» Reject if too shallo Pass Fail

19 Performance» HDAO (depth onl): and normals): Direct3D 0.0: MS Direct3D 0.: MS MS FPS HDAO 0.0 s 0. (280024) HDAO Off HDAO Depth HDAO Depth Normals Direct3D Direct3D Phenom 2.3GHz, HD4870X2, 2 GB RAM, Windos Vista 32 (SP)

20 Tom Clanc s HAWX Publisher: Ubisoft Deeloper: Ubisoft Romania HDAO is onl applied to the terrain and buildings (not the aeroplane)

21 Stormrise Publisher: SEGA Deeloper: The Creatie Assembl Australia

22 BattleForge Publisher: EA Deeloper: EA Phenomic

23 Future Wor» Looing into a compute shader accelerated ersion Solid sampling pattern lends itself ell to Thread Local Storage» Account for strong light sources AO for man scenes is not lo frequenc» Real alle tracing...

24 High Qualit Shado Filtering

25 Ho Direct3D 0. helps filtering for single channel tetures Direct3D 0.0 Direct3D 0. z z z z NN point samples if ou need all data points e.g. 44 = 6 (N/2)(N/2) Gather operations get all data - e.g. 22 = 4

26 Wh reisit conentional shado filtering? -» There are adanced techniques for smooth shados» The most prominent are» VSMs, laered VSMs, CSMs, ESMs, ACDF SMs» Can be combined ith SATs for arbitar smoothness» But these methods bring other problems» The renderer gets more comple» Ma need to or around specific artifacts» Use onl if neccessar

27 Wh reisit conentional shado filtering? - 2» Adanced methods come at a cost» More RTs at a high memor cost» Costl postprocessing operations» Non optimal RT formats» Is an adanced techique needed?» Depth buffer based deferred shadoing does not depend on depth compleit» Big conentional shado filters not that epensie

28 Surprising insights about uniform shado filtering Let s filter a 44 isibilit sample bloc Direct3D 0. Direct3D 0.0 z z z z 4 Gather operations plus some ALU (N/2)(N/2) Gather ops for NN 9 PCF samples plus some ALU right?

29 Surprising insights about uniform shado filtering Let s filter a 44 isibilit sample bloc Direct3D 0. Direct3D 0.0 z z z z NO! 4 Gather operations plus some ALU (N/2)(N/2) Gather ops for NN 9 PCF samples plus some ALU right?

30 Surprising insights about uniform shado filtering Let s filter a 44 isibilit sample bloc Direct3D 0. Direct3D 0.0 z z z z 4 Gather operations plus some ALU => (N/2)(N/2) Gather() samples for NN 4 shifted PCF samples plus a post eight factor is enough => (N/2)(N/2) PCF samples for NN

31 Surprising insights about uniform shado filtering 2 Let s loo at onl ro of 4 isibilit samples ( ) 0 ( ) 2 ( ) 2 3 Simplifies to ( ) ( ) p (( ) 0 ) ( ( ) 2 3) p Credit for this idea goes to: Serge Nenaho at Funcom

32 Surprising insights about uniform shado filtering 3» Onl (N/2)(N/2) PCF samples necessar instead for a uniform filter» Cheaper than commonl assumed» 88 ith onl 6 PCF samples» Not onl for shado filtering» Same teture op count as Direct3D 0.» Wh bother ith Direct3D 0.?

33 From DICE s Frostbite Engine: Uniform shado filtering

34 From DICE s Frostbite Engine: Gaussian shado filtering

35 Disadantages of uniform shado filtering Uniform filtering blurs aa too man details Gaussian filtering preseres more details

36 Adanced Direct3D 0. shado filtering Use a unique eight per PCF sample

37 Adanced Direct3D 0. shado filtering Use a unique eight per PCF sample

38 Adanced Direct3D 0. shado filtering Use a unique eight per PCF sample ( N ) ( N ) = 0 ( N ) ( N ) = 0 pcf

39 Adanced Direct3D 0. shado filtering 2» Direct3D 0. needs (N/2)(N/2) Gather() samples» A (N/2)(N/2) PCF samples solution is no longer possible for unique eights» Filter eights are not smmetric» Equation sstem not solable» It is possible to get belo NN PCF ops for Direct3D 0.0 though

40 Adanced Direct3D 0. shado filtering 3 Let s filter a 44 isibilit sample bloc using unique eights Direct3D 0. Direct3D 0.0 z z z z 4 Gather() operations plus some ALU => (N/2)(N/2) Gather samples for NN 9 PCF samples plus some ALU right?

41 Adanced Direct3D 0. shado filtering 3 Let s filter a 44 isibilit sample bloc using unique eights Direct3D 0. Direct3D 0.0 z z z z NO! 4 Gather() samples plus some ALU => (N/2)(N/2) Gather() samples for NN 9 PCF samples plus some ALU right?

42 Adanced Direct3D 0. shado filtering 3 Let s filter a 44 isibilit sample bloc using unique eights Direct3D 0. Direct3D 0.0 z z z z 4 Gather() samples plus some ALU => (N/2)(N/2) Gather() samples for NN 6 shifted PCF samples plus post eight factors is enough => (N/2)(N-) PCF samples for NN

43 Adanced Direct3D 0. shado filtering ) ( 2 ) ( ) ( ) ( ) ( ( ) ( ) 2 N- N ) - ( = N ( ) ( ) ' p = ( ) ( ) 0 ' p = ( ) ( ) ) ( left ( ) 0 0 ' = 0 p =

44 Adanced Direct3D 0. shado filtering ) ( 2 ) ( ) ( ) ( ) ( ( ) ( ) 2 N- N ) - ( = N ( ) ( ) ) ( left ( ) ( ) ( ) ( ) center ( ) ( ) ( ) p = ' ( ) ( ) ' = p ( ) ( ) = ' ( ) p =

45 Adanced Direct3D 0. shado filtering ) ( 2 ) ( ) ( ) ( ) ( ( ) ( ) 2 N- N ) - ( = N ( ) ( ) ) ( left ( ) ( ) ( ) ( ) center ( ) ( ) 2 2 N N N N N N right ( ) ( ) ( ) ' = N N N N N p ' = N N N p 2 ' = N N N 2 = N N p

46 Adanced Direct3D 0. shado filtering 5» Direct3D 0.0» needs (N/2)(N-) PCF samples for Gaussian shados not (N-)(N-)!» can do one ro ith (N/2) samples ith shifted teture coords» teture coord stas untouched» Stats of an optimized shader for 88» Direct3D 0. shader roughl tice as fast as the Direct3D0.0 ersion» Direct3D 0. shader as fast as the optimized uniform (N/2)(N/2) filter under Direct3D0.0

47 From DICE s Frostbite Engine: Standard 22 shado filtering

48 From DICE s Frostbite Engine: 55 Gaussian filtering

49 Tom Clanc s HAWX Publisher: Ubisoft Deeloper: Ubisoft Romania Normal Qualit Blurred VSM

50 Tom Clanc s HAWX Publisher: Ubisoft Deeloper: Ubisoft Romania Gaussian Shados

51 Stormrise, Publisher: SEGA Deeloper: The Creatie Assembl Australia Normal Shado Qualit

52 Stormrise, Publisher: SEGA Deeloper: The Creatie Assembl Australia Gaussian Shados

53 Summar:» HDAO adds enourmous depth to the scene, at an affordable cost» Using Direct3D 0. gather4 instruction greatl accelerates performance» Groing number of game deelopers using the effect» Mail if ou ould lie to no more...

54 Summar: 2» Conentional high qualit shado filtering is suprisingl fast» Een under Direct3D 0.0/9» Direct3D 0. deliers the best performance» No reason not to use gaussian shados!» Direct3D supports Gather()!» Mail if ou ant the shaders or the deriations for (N/2)(N/2) PCF sample shados

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