Introduction to Powervr Ray Tracing Tuesday 18Th March, 2014 @ GDC

Introduction to PowerVR Ray Tracing Tuesday 18th March, 2014 @ GDC

James A. McCombe What are we launching today? Host CPU Control and Register Bus System Interface Memory Interface

Vertex Uniﬁed Shading Cluster Array Data Master

Texture USC0 USC1 Pixel Unit Data Master Course Grain Scheduler ... Core Compute Management Data Master Texture USCn-1 USCn Memory Ray Unit Cache Unit Data Master

Ray Tracing Unit

Intersection Scene Frame Coherency Engine Tiling Co- Pixel Co- 2D Core Processor Array Hierarchy Accumulator processor Processor (PTLA) Generator Cache System Memory Bus

What are the applications for this?

Augmented Reality

Image and Diagram Copyright Peter Kán 2012 Virtual Reality a.k.a Multi-persective rendering

Lens distortion and aberration correction

Lenticular Displays

Ultra-low latency rendering Hybrid rendering in games

• Shadows • Reﬂections • Transparency • Better scaling with multiple dynamic lights • Real-time light map updates for the rasteriser • Easy to bolt on Fully ray traced graphics

• Brute force path tracing • Produces photo realism easily • Pretty much requires all the 3D content to be ray traced • Possible in todays technology in console / desktop using Wizard • Probably not practical for fully real-time use in mobile for a couple more generations. Fine for sub-realtime use. Non-graphics

• Better in-game AI • Collision Detection • 3D spatial search Overview of PowerVR Power and Bandwidth

300W 300Gb/s 270Gb/s 240Gb/s 225W 210Gb/s 180Gb/s 150W 150Gb/s 120Gb/s 90Gb/s 75W 60Gb/s 30Gb/s 0W 0Gb/s Workstation Mobile Workstation Laptop Light Laptop Tablet

Graphics Watts Graphics Bandwidth Capability of our mobile graphics 150

112.5

• Almost 5x compute capability 75 • 4x vec4 MAD → 16x Scalar 2xMAD

Shader GFlops • 1.5 → 3.6 Gtexels/s 37.5 • OpenGLES 3.0 Support

0 2006 2007 2008 2009 2010 2011 2012 2013 Host CPU Control and Register Bus System Interface Memory Interface

Vertex Uniﬁed Shading Cluster Array Data Master

Texture USC0 USC1 Pixel Unit Data Master Course Grain Scheduler ... Core Compute Management Data Master Texture USCn-1 USCn Memory Unit Cache Unit

Tiling Co- Pixel Co- 2D Core processor Processor (PTLA) System Memory Bus Vertex Task Vertex Data Master 32 Instances Uniﬁed Shading Cluster Array

Pixel Task Texture USC0 USC1 Pixel Unit Data CGS Master 32 Instances Texture USCn-1 USCn Compute Task Unit Compute Data Master 32 Instances

• An instance is a vertex, pixel or OpenCL thread • All instances in the task share Program, Uniforms, Parameters, etc. Shader Uniforms and Constants Common Store Registers (Shared across instances in the task)

Common Instruction ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU

Per Pixel / Vertex data and shader temps

Uniﬁed Store Registers (Private registers per instance)

(not exact) ABS, Source 0 NEG, etc. ⩽ 2 Flops

ABS, Integer Math Source 1 Output 0 NEG, etc. Format ABS, Conversions Source 2 NEG, etc. Format Comparison Conversions ABS, Source 3 NEG, etc.

ABS, Source 4 ⩽ 2 Flops Output 1 NEG, etc.

ABS, Source 5 NEG, etc.

12 Cycles of Latency (not exact) Common Store Registers (Shared across instances in the task)

Common Instruction ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU ALU

varying vec2 texCoord; void main() { if (texCoord.x > 0.5) { ...... } else { ... Uniﬁed Store Registers (Private registers per instance) ... } Overall capability

• Series6 gives you over 100Gﬂops for shading on latest mobile devices • OpenGL ES 3.0 support • Massive capability gain allowing math heavy shaders • Mobile graphics is where the actual innovation is happening • Try it! A Technical introduction to Wizard Host CPU Control and Register Bus System Interface Memory Interface

Vertex Uniﬁed Shading Cluster Array Data Master

Texture USC0 USC1 Pixel Unit Data Master Course Grain Scheduler ... Core Compute Management Data Master Texture USCn-1 USCn Memory Ray Unit Cache Unit Data Master

Ray Tracing Unit

Intersection Scene Frame Coherency Engine Tiling Co- Pixel Co- 2D Core Processor Array Hierarchy Accumulator processor Processor (PTLA) Generator Cache System Memory Bus Host CPU Control and Register Bus System Interface Memory Interface

Vertex Uniﬁed Shading Cluster Array Data Master

Texture USC0 USC1 Pixel Unit Data Master Course Grain Scheduler ... Core Compute Management Data Master Texture USCn-1 USCn Memory Ray Unit Cache Unit Data Master

Ray Tracing Unit

Intersection Scene Frame Coherency Engine Tiling Co- Pixel Co- 2D Core Processor Array Hierarchy Accumulator processor Processor (PTLA) Generator Cache System Memory Bus ABS, Source 0 NEG, etc. ⩽ 2 Flops

ABS, Integer Math Source 1 Output 0 NEG, etc. Ray RAM Format ABS, Conversions Source 2 NEG, etc. Format Comparison Conversions ABS, Source 3 NEG, etc.

ABS, Source 4 ⩽ 2 Flops Output 1 NEG, etc. Ray RAM

ABS, Source 5 NEG, etc.

12 Cycles of Latency (not exact) New shader type

• Ray Shaders are invoked when a ray intersects a triangle • Shaders types can emit any number of rays • OpenRL has a frame shader to emit primary rays • Existing fragment / pixel shaders can emit rays also!

• GLSL Programming model is the same • Built-in functions, parameters, etc. Primitive Objects

• Encapsulate the rendering state for one mesh • Includes VBOs, uniforms, shader programs, texture bindings, etc. • Ray tracing unit sorts rays into tasks with common primitive objects

• Persistent between frames • Mutable objects by the client Constraints / Limitations

• Shaders cannot wait for results of individual ray trace operations • Shaders must provide a worst case estimate on number of child rays • Per-ray user data payload must be carefully managed Task 0 Parallelism is on rays NOT pixels

Task 1 Common Instruction ALU ALU ALU ALU

(In this example, ALU width is 4 to make the diagram smaller) Task 2

Task 3 Parallelism is on rays NOT pixels Relief: Quick ray emission demo Intersection Processor Array or “Who needs Fixed Function?” Ray:AABB Test

• “Fast Ray-Axis Aligned Bounding Box Overlap Tests with Plucker Coordinates.” – Jeffrey Mahovsky and Brian Wyvill • 6 lines form the silhouette of the AABB • 6 planes from the ray origin and each edge vector • Dot product of plane normal and ray direction vector • 6 signs must match and be negative. Ray distance setup Translation Box Plane Setup Plane tests Test Combine

0 XB >7

invert voxel_center_x shift_center_x7+/! XA cov_convert ri(31) ri(31) ! AX0min origin_x XB BX0max XA

Octant(0) >7 origin_x_miss ri invert

ri(31) ri(31)

endpt_x_miss 0 YB dirx >7

ri invert x voxel_center_y shift_center_y7+/! YA ray_distance Hit cov_convert rj(31) rj(31) origin_y_miss MISS ! AY0min endpt_y_miss origin_y YB BY0max YA diry or Octant(1) >7 rj x rj origin_z_miss ray_distance invert Miss rj(31) rj(31)

dirz

rk 0 x ZB ray_distance >7 endpt_z_miss !

invert voxel_center_z shift_center_z7+/! ZA cov_convert rk(31) rk(31) ! AZ0min origin_z ZB BZ0max ZA Octant(2) >7 rk invert rk(31) rk(31) ! 3 MUL 6 SUB 6 ADD 12 MUL 6 bitwise OR USC instruction group packing

LD MUL ADD MUL OR LD MUL ADD MUL – LD MUL ADD MUL OR LD SUB ADD MUL – 26 Instructions LD SUB ADD MUL OR LD SUB ADD MUL – (32 if using compressed SUB MUL OR data formats) SUB MUL – SUB MUL OR – MUL – MUL OR MUL – 44x less area for this function

USC USC USC USC USC USC USC USC

USC USC USC USC USC USC USC USC Tester and Rays Tester and Rays Box Box Box Box vs. vs. vs. vs. Ray Ray Ray Ray

Box Box Box Box vs. vs. vs. vs. Ray Ray Ray Ray

Box Box Box Box vs. vs. vs. vs. Child Ray Ray Ray Ray Address Coherence Cache

2 7 2 4 2 2

Box Box Box Box 2 2 1 5 vs. vs. vs. vs. 5 2 3 2 1 2 Ray Ray Ray Ray Free Queue 5 3 1 2

Box 5 2 7 7 2 5 Triangle vs. Ray Triangle vs. Ray Hits Old Count Existing Queue

Queue Packer

Tester and Rays Tester and Rays Inst Data Inst Data

Box Box Box Box Update Update vs. vs. vs. vs. Existing New Ray Ray Ray Ray Queue Queue

Box Box Box Box Coherence Queue RAM vs. vs. vs. vs. Ray Ray Ray Ray

Box Box Box Box vs. vs. vs. vs. Ray Ray Ray Ray

USC USC USC USC USC USC USC Box Box Box Box vs. vs. vs. vs. Ray Ray Ray Ray

Triangle vs. Ray Triangle vs. Ray

USC USC USC USC USC USC USC

USC USC USC USC USC USC USC The Ray Tracing Unit and Coherence Engine Uniﬁed Shading Cluster Array System Memory Interface Texture USC0 USC1 Unit Course Ray Grain Data Master Scheduler

Texture USCn-1 USCn Unit

Rays grouped by PrimitiveObject Rays in arbitrary order (Shader + Resources)

Ray Tracing Unit

Intersection Coherency Engine Processor Array

System Memory Bus AABB Blocks Vertex Blocks Varyings

Ascending Virtual Memory Addresses

( around 100Mbytes for 1M triangles including varyings ) Primitive Primitive Object 1 Object 2

PrimitiveObject 0 node_13994 node_7671 node_7961 node_18458 node_6085 node_6099 node_7905 node_7861 node_8654 node_8606 node_7124 node_9423 node_7289 node_11312 node_8862 node_8876 node_10504 node_9245

node_8261 node_7666 node_7956 node_6080 node_6094 node_7900 node_7856 node_8649 node_8601 node_7119 node_7364 node_7284 node_9199 node_8857 node_8871 node_8655 node_6468

node_12112 node_18453

node_22355 node_22359 node_22487 node_22490 node_22497

node_22369 node_22372 node_22404 node_22409 node_22510 node_22502

node_22418 node_22517 node_22528 node_22543 node_13993 node_22290

node_16991 node_11714 node_16984 node_22423 node_22533 node_22550 node_19252 node_19955

node_6445 node_16994 node_6436 node_16999 node_6428 node_11716 node_16978 node_11718 node_16981 node_16986 node_14127 node_22558 node_8356 node_8725 node_19374 node_21187 node_21196 node_21326 node_22294 node_22307 node_21211

node_6450 node_6452 node_6438 node_6440 node_6430 node_11722 node_6432 node_6424 node_11732 node_17005 node_17121 node_22561 node_8412 node_9046 node_9110 node_21192 node_21202 node_21331 node_21338 node_21237 node_21354 node_22311 node_22317 node_22431 node_21216 node_21293 node_21571 node_21383 node_22263 node_22274 node_22279 node_19959

node_6456 node_6442 node_11744 node_6434 node_11726 node_6426 node_11730 node_13585 node_13707 node_9221 node_21343 node_21658 node_21663 node_21822 node_21242 node_21260 node_21890 node_21360 node_21369 node_21489 node_22300 node_22323 node_22459 node_21225 node_21300 node_21311 node_21581 node_21793 node_21388 node_21396 node_21413 node_22268 node_22282 node_19964 node_19974 node_19975 node_20031

node_13629 node_13503 node_17200 node_19064 node_7854 node_18926 node_21672 node_21834 node_21249 node_21270 node_21278 node_21904 node_21917 node_21374 node_21503 node_21969 node_22041 node_16820 node_22438 node_22446 node_22474 node_21229 node_21316 node_21641 node_21577 node_21799 node_21808 node_21402 node_21475 node_21419 node_21426 node_21947 node_22332 node_6345 node_12822 node_19981 node_19984 node_20042

node_7590 node_7638 node_8136 node_19307 node_8219 node_8344 node_8549 node_19067 node_7502 node_13393 node_17123 node_21677 node_21828 node_21253 node_21284 node_21685 node_21730 node_21746 node_21897 node_21924 node_21933 node_21496 node_21983 node_22102 node_22053 node_22057 node_22073 node_21516 node_22451 node_22467 node_19254 node_21598 node_21623 node_21876 node_21589 node_21813 node_21442 node_21447 node_21480 node_22028 node_21431 node_21950 node_21955 node_22335 node_22340 node_22381 node_20037 node_20056 node_20067 node_19853

node_7608 node_13788 node_7676 node_13868 node_7696 node_8290 node_14009 node_8362 node_8774 node_19446 node_8394 node_8998 node_9102 node_7544 node_13643 node_7586 node_7622 node_13887 node_19311 node_13455 node_16862 node_13523 node_17007 node_17203 node_21839 node_18928 node_21751 node_21910 node_21938 node_21509 node_21977 node_22047 node_22066 node_21521 node_21540 node_10766 node_16823 node_11100 node_10782 node_16854 node_22480 node_18988 node_21608 node_21647 node_21846 node_21862 node_21881 node_18531 node_21455 node_21463 node_21997 node_22002 node_22032 node_21960 node_22079 node_22082 node_22345 node_22384 node_22389 node_16766 node_20047 node_20061 node_19804 node_19814 node_19831

node_7714 node_13977 node_8419 node_9065 node_9116 node_9213 node_14080 node_7606 node_13722 node_7662 node_13802 node_17454 node_19703 node_11809 node_17503 node_11843 node_19203 node_21692 node_21702 node_21736 node_19017 node_19161 node_19283 node_21989 node_22108 node_22115 node_18215 node_21530 node_21548 node_21557 node_22191 node_11102 node_16838 node_11104 node_10804 node_16827 node_10833 node_10965 node_11094 node_16857 node_21630 node_21854 node_21867 node_18476 node_22011 node_22018 node_22129 node_22174 node_22180 node_22092 node_22094 node_22393 node_6335 node_16755 node_12588 node_16753 node_20073 node_19838 node_19858 node_11473

node_9228 node_11822 node_17816 node_19069 node_21713 node_21760 node_21766 node_17877 node_19020 node_22120 node_21533 node_21562 node_22236 node_11106 node_16841 node_10853 node_16831 node_11031 node_19643 node_16843 node_16850 node_19131 node_14145 node_18500 node_19244 node_22143 node_22156 node_22163 node_6337 node_12690 node_6339 node_6331 node_12766 node_16792 node_12606 node_16748 node_12634 node_16751 node_19867 node_11477 node_15940

node_11835 node_17555 node_6602 node_6594 node_6620 node_17935 node_19071 node_13885 node_19313 node_21777 node_21782 node_17818 node_13947 node_19413 node_18068 node_12072 node_13427 node_18074 node_18276 node_22194 node_22242 node_11096 node_19259 node_13945 node_19377 node_19380 node_19403 node_14131 node_14139 node_13205 node_18559 node_18561 node_18982 node_17990 node_17774 node_6341 node_12720 node_6333 node_12744 node_12403 node_16771 node_16773 node_16759 node_12413 node_16786 node_19624 node_12405

node_6604 node_11863 node_6596 node_11883 node_6598 node_6624 node_11926 node_6630 node_6608 node_17998 node_18933 node_13389 node_11756 node_11846 node_17821 node_6511 node_17939 node_18000 node_5839 node_18071 node_5814 node_18146 node_5852 node_12080 node_18344 node_12093 node_18591 node_13489 node_16946 node_13565 node_11674 node_18640 node_18077 node_19024 node_19285 node_12982 node_22251 node_11098 node_11108 node_16846 node_19264 node_19272 node_19385 node_13922 node_19406 node_18993 node_7950 node_19157 node_14134 node_12102 node_13171 node_13189 node_13423 node_13415 node_18536 node_19224 node_17711 node_16762 node_12415 node_12407 node_16779 node_12409 node_9752 node_15943 node_11489 node_15987 node_11023 node_16006

node_6600 node_11903 node_6634 node_6610 node_6612 node_7722 node_18937 node_18944 node_19077 node_19206 node_13451 node_16866 node_11760 node_17262 node_17255 node_12594 node_17507 node_17388 node_11848 node_12706 node_17825 node_17828 node_6517 node_11929 node_6521 node_17941 node_18003 node_5842 node_5844 node_5820 node_5824 node_5854 node_11988 node_5856 node_5848 node_12049 node_18275 node_13617 node_17092 node_11705 node_18688 node_19784 node_18149 node_18221 node_12964 node_18279 node_19028 node_13000 node_18376 node_22201 node_22210 node_22256 node_7692 node_13750 node_19275 node_13933 node_19394 node_13830 node_9106 node_18999 node_19006 node_19136 node_8245 node_8346 node_18661 node_13004 node_18680 node_12108 node_13028 node_18630 node_13230 node_19762 node_13179 node_18427 node_13193 node_18348 node_13197 node_13485 node_16922 node_13477 node_16940 node_13546 node_18240 node_18254 node_18265 node_18135 node_18207 node_18540 node_18547 node_18566 node_18481 node_19228 node_19235 node_19340 node_13904 node_19363 node_19366 node_18958 node_17970 node_19744 node_17648 node_12598 node_17754 node_12411 node_16783 node_16554 node_9818 node_16574 node_9894 node_10927 node_15947 node_11012 node_15953 node_10947 node_15989 node_15994 node_16008

node_6616 node_7738 node_8332 node_7766 node_18948 node_8439 node_19082 node_19091 node_19210 node_13645 node_19217 node_19317 node_17010 node_11764 node_12354 node_11749 node_12622 node_17509 node_12646 node_17558 node_17390 node_17328 node_17361 node_6491 node_11869 node_17833 node_17883 node_6525 node_17944 node_5846 node_5832 node_11979 node_5858 node_12011 node_5850 node_12031 node_18082 node_5669 node_18151 node_18155 node_5687 node_11994 node_18224 node_18284 node_19166 node_13949 node_19416 node_13024 node_18595 node_22218 node_18863 node_7710 node_13760 node_7688 node_7634 node_13671 node_13924 node_9112 node_9104 node_19009 node_19145 node_8396 node_14101 node_13008 node_18665 node_12990 node_18671 node_12986 node_18683 node_13032 node_13044 node_13274 node_18623 node_13266 node_18637 node_17174 node_18436 node_13201 node_18402 node_13481 node_16925 node_13613 node_17066 node_13607 node_17086 node_18244 node_18256 node_5680 node_18267 node_18311 node_18323 node_18334 node_18111 node_6090 node_12136 node_18550 node_13137 node_18572 node_18578 node_6134 node_18486 node_5734 node_18494 node_18505 node_13732 node_19238 node_13908 node_19346 node_19352 node_8338 node_18963 node_18972 node_19103 node_19116 node_8441 node_19127 node_17974 node_17981 node_18034 node_12779 node_18058 node_18061 node_17850 node_17859 node_6532 node_17871 node_12426 node_12630 node_17285 node_11805 node_12626 node_17302 node_17758 node_17765 node_17781 node_11801 node_17806 node_17808 node_17691 node_9822 node_9756 node_16559 node_9835 node_16564 node_16693 node_9958 node_16716 node_10931 node_10919 node_11008 node_15956 node_11481 node_15997 node_11016 node_11638

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Primitive Primitive Object 1 Object 2

PrimitiveObject 0 (coherence queues)

Primitive Primitive Object 1 Object 2

PrimitiveObject 0 Automatically ﬁnds coherence paths The Scene Hierarchy Generator Uniﬁed Shading Cluster Array System Memory Interface Texture USC0 USC1 Unit Course Vertex Grain Data Master Scheduler

Texture USCn-1 USCn Unit

World-space Triangles and associated varyings

Scene Hierarchy Generator

System Memory Bus Limitations

• Scene is represented by triangles – same as today • BVH is in a deﬁned format optimised for construction and traversal • Triangle order must generally follow a spatially coherent ﬂow • An approximate scene scale estimation is needed • Geometry shaders are not inline with the ray tracing pipeline Strengths • Shading cluster workload is no higher than a vertex shader • Only needs to process geometry that actually moved in world space • Unique algorithm constrains working set to internal registers only • Single pass operation: in-line with vertex shader execution • Handles the “long skinny triangles” problem well • Streaming writes to external memory • Losslessly compressed output formats due to build algorithm • Compact logic Built on sparse log2 oct-tree scaffolding

LODLevel = = 1 1 LODLevel = = 2 2 LODLevel == 33 For each VBExtents triangle Foreach Select LOD VBNode in LOD

v2 Compute Parent Voxel

Per LOD v1 VBNode VBNode On VoxelCache v0 linked list HIT Pool head pointers

Add Output Scene VBNode Acceleration Leaf Tree Structure VoxelCache VoxelCache GenerateVBNode() On evictionOn On evictionOn

ProcessTriangle() AssembleParents() After some triangles...

LOD10 Leaf Head LeafCount=3 TreeCount=0 Tree Head

LOD14 Leaf Head LeafCount=0 TreeCount=0 Tree Head

LOD15 Leaf Head LeafCount=3 TreeCount=0 Tree Head

LOD16 Leaf Head LeafCount=8 TreeCount=0 Tree Head Assembling parents...

LOD10 Leaf Head LeafCount=3 TreeCount=0 Tree Head

LOD14 Leaf Head LeafCount=0 Tree Head VBNode TreeCount=0 Pool

LOD15 Leaf Head LeafCount=3 TreeCount=0 Tree Head Add VBNode to linked list of VBNodes for its LOD LOD16 Leaf Head LeafCount=8 TreeCount=0 Tree Head GenerateVBNode()

On eviction

Tree VoxelCache

Flush Leaf Nodes After parents for one level have been assembled...

LOD10 Leaf Head LeafCount=3 TreeCount=0 Tree Head

LOD14 Leaf Head LeafCount=0 TreeCount=0 Tree Head

LOD15 Leaf Head LeafCount=3 A B C TreeCount=0 Tree Head

LOD16 Leaf Head LeafCount=8 A0 A1 B0 C0 C1 B1 B2 C2 TreeCount=0 Tree Head Performance Expectations Host CPU Control and Register Bus System Interface Memory Interface

Vertex Uniﬁed Shading Cluster Array Data Master

Texture USC0 USC1 Pixel Unit Data Master Course Grain Scheduler ...128 Inst/ray Core Compute Management Data Master (512ﬂops peak) Texture USCn-1 USCn Memory Ray Unit Cache Unit Data Master

1-2 clk/ray Ray Tracing Unit 6 clk/tri 1-2clk/accum

Intersection Scene Frame Coherency Engine Tiling Co- Pixel Co- 2D Core Processor Array Hierarchy Accumulator processor Processor (PTLA) 64 AABB/ray Generator Cache System Memory Bus 16 Tri/ray Get early access to the programming concepts at: http://tinyurl.com/9ddlsv2

Talk immediately after this on Hybrid rendering

See the demos at Imagination Booth #402 South Hall QA Thank you