Post on 17-Oct-2020
Martin Stich, Engineering Manager
INTRODUCTION TO OPTIX
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AGENDA
OptiX Basics
Advanced Topics
Case Studies
Feature Outlook
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OPTIX BASICS
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IN A NUTSHELL
State-of-the-art performance: 500M+ rays/sec
Algorithm and hardware agnostic
Shaders with single-ray programming model, recursion
Available free for private and commercial use
The OptiX Ray Tracing SDK
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RELEASE TIMELINE
Jan 2016 Summer 2016 TODAY!
OptiX 3.9Pascal Support
OptiX 4.0LLVM PipelineNVLINK Scaling
OptiX 4.1Performance
CUDA 8, VS2015
2009
OptiX 1.0Hello World!
...
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MODERN RAY TRACING
Rasterization:
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MODERN RAY TRACING
Rasterization:
Ray Tracing:
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THE RAY TRACING PIPELINE
Programmable:
Ray Generation
Closest Hit, Any Hit, Miss
Intersection
← Launch entry
← Shading
← GeometryRAY GENERATION
INTERSECTIONANY-HIT
INTERSECTIONANY-HIT
CLOSEST-HIT
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MAIN OPERATIONS
RAY GEN INTERSECT ANY HIT CLOSEST HIT MISS
rtTrace ✔ ✔ ✔
rtPotentialIntersection ✔
rtReportIntersection ✔
rtIgnoreIntersection ✔
rtTerminateRay ✔
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SHADER COMMUNICATION
Variables
similar to uniforms in other systems
constants, system values, buffers, textures, …
Example:
Textures
Current ray
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SHADER COMMUNICATION
Variables
similar to uniforms in other systems
constants, system values, buffers, textures, …
Ray Payload
arbitrary data associated with ray
in/out from rtTrace to Any-hit, Closest-hit, Miss
Example:
Textures
Current ray
Example:
Color data
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SHADER COMMUNICATION
Variables
similar to uniforms in other systems
constants, system values, buffers, textures, …
Ray Payload
arbitrary data associated with ray
in/out from rtTrace to Any-hit, Closest-hit, Miss
Attributes
arbitrary data associated with hit
generated in Intersection program
consumed by Any-hit, Closest-hit
Example:
Color data
Example:
Barycentrics
Example:
Textures
Current ray
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EXAMPLE
See optixPathTracer SDK sample for a slightly less minimalistic version
Miniature Path Tracer
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GLOBAL ILLUMINATION
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GLOBAL ILLUMINATION
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GLOBAL ILLUMINATION
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GLOBAL ILLUMINATION
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HOWEVER…
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RAY PAYLOAD
struct RayPayload{
float3 radiance; // stores contribution after we hit the light source
float3 attenuation; // accumulated attenuation of radiance due to materials
float3 next_origin; // reflection ray to be traced for the nextfloat3 next_direction; // ..segment of the path
unsigned seed; // random number generator state
bool done; // whether we’re done tracing this path
};
Path State Definition
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INTEGRATIONRT_PROGRAM void ray_generation(){
unsigned int seed = tea<16>( launch_index.x + launch_index.y*output_buffer.size().x, frame_number );float3 ray_origin = eye;float3 ray_direction = compute_jittered_ray_dir( seed );
RayPayload payload;payload.radiance = make_float3(0,0,0);payload.attenuation = make_float3(1,1,1);payload.seed = seed;payload.done = false;int depth = 0;
while( !payload.done && depth++ < 10 ){
Ray ray = make_Ray( ray_origin, ray_direction, 0, 0.001f, RT_DEFAULT_MAX );
rtTrace( scene, ray, payload );
ray_origin = payload.next_origin;ray_direction = payload.next_direction;
}
const float3 result = payload.radiance * payload.attenuation;
const float lerp_t = frame_number > 1 ? 1.0f / frame_number : 1.0f;const float3 prev_col = make_float3( output_buffer[launch_index] );output_buffer[launch_index] = make_float4( lerp( prev_col, result, lerp_t ), 1.0f );
}
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rtDeclareVariable( float3, diffuse_color, , );rtDeclareVariable( float3, normal, attribute normal, );rtDeclareVariable( optix::Ray, ray, rtCurrentRay, );rtDeclareVariable( float, t_hit, rtIntersectionDistance, );rtDeclareVariable( RayPayload, current_payload, rtPayload, );
RT_PROGRAM void closest_hit_diffuse(){
const float3 hitpoint = ray.origin + t_hit * ray.direction;
const float z1 = rnd( current_payload.seed );const float z2 = rnd( current_payload.seed );float3 dir;cosine_sample_hemisphere( z1, z2, dir );optix::Onb onb( normal );onb.inverse_transform( dir );
current_payload.next_origin = hitpoint;current_payload.next_direction = dir;
current_payload.attenuation *= diffuse_color;}
DIFFUSE MATERIAL
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rtDeclareVariable( RayPayload, current_payload, rtPayload, );rtDeclareVariable( float3, emission_color, , );
RT_PROGRAM void closest_hit_light(){
current_payload.radiance = emission_color;current_payload.done = true;
}
RT_PROGRAM void miss(){
current_payload.radiance = make_float3(0,0,0);current_payload.done = true;
}
LIGHT MATERIAL AND MISS
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rtDeclareVariable( float3, anchor, , );rtDeclareVariable( float3, v1, , );rtDeclareVariable( float3, v2, , );rtDeclareVariable( float4, plane, , );rtDeclareVariable( float3, normal, attribute normal, ); rtDeclareVariable( optix::Ray, ray, rtCurrentRay, );
RT_PROGRAM void intersect( int primIdx ){
const float3 n = make_float3( plane );const float dt = dot( ray.direction, n );const float t = (plane.w - dot(n, ray.origin)) / dt;const float3 p = ray.origin + ray.direction * t;const float3 vi = p - anchor;const float a1 = dot( v1, vi );const float a2 = dot( v2, vi );
if( a1 >= 0 && a1 <= 1 && a2 >= 0 && a2 <= 1 ){
if( rtPotentialIntersection( t ) ){
normal = n;rtReportIntersection( 0 );
}}
}
SCENE GEOMETRY
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RESULTAccumulation Over Time
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NEXT STEP IDEAS
Next event estimation
Russian roulette
Sphere primitives
Mirror material
Glass material
Triangle meshes
Environment maps
...
Mini Path Tracer Reader Exercises
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NODE GRAPH
Context
Geometry Group
Geometry
Instance
Geometry
Material
Group
Variables
Intersection Program
Any Hit +Closest Hit
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ADVANCED TOPICS
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INTEROPShare CUDA and OpenGL Resources
CUDA
Share CUDA allocations
rtBufferSetDevicePointerrtBufferGetDevicePointer
OpenGL
Share textures and vertex buffers
rtBufferCreateFromGLBOrtTextureSamplerCreateFromGLImage
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BINDLESS OBJECTS
“Bindless”: powerful concept to dynamically select textures, buffers, and programs at runtime
Allows efficient implementation of large shading networks
Reduces code size, compile times, and number of compiles
Pixar Animation Studio’s “Flow” material editing tool. Visit the NVIDIA website to watch a SIGGRAPH 2015 talk describing the system in detail.
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PTX GENERATIONOptions
OptiX
nvcc.exe
nvrtc.dll
NVVM/
NVPTX
CUDA-C++
CUDA-C++
LLVM-IR
PTX
Offline
JIT
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MULTI-GPU AND NVLINKAutomatic Scaling
110M Triangles
23M Grass Blades
15GB Textures
2 x GP100
Monsters University data set courtesy of Pixar Studios
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REMOTE RENDERINGOn Quadro VCA or DGX-1
Progressive
video stream
Incremental
updates
OptiX App
OptiX Server(s)
ETHERNET
INTERNET
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OPTIX PRIME
Supports instancing, async operations, ray masks
Performance similar to OptiX
Same semantics via OptiX: See optixRaycasting sample
Simple intersection-only API
Rays
Triangles
OptiX
Prime
GPU or CPU
Intersections(primIdx, t, u, v)
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CASE STUDIES
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PERFORMANCERaw Traversal on Titan X Pascal
+16% in OptiX 4.1+3% in OptiX 4.1
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NVIDIA: IRAY & MENTAL RAY
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NVIDIA: GVDB
Image Property of DreamWorks AnimationOpenVDB format support
Live interaction with multiple-bounce GI scattering, 10x-30x faster than CPU
Introduction and Techniques with NVIDIA GVDB VoxelsMonday, 9:00 AM – Room 231
Sparse Volume Rendering
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AAA-STUDIO: FURRYBALL PRODUCTION RENDERING
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VISUAL MOLECULAR DYNAMICS (VMD)
Molecular Visualization package with hundreds of thousands of users
Developed by John Stone of U Illinois
Cutting Edge OptiX Ray Tracing Techniques for Visualization of Biomolecular and Cellular Simulations in VMDTuesday, 3:30 PM – Room 230C
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OLCF: SCIENTIFIC VISUALIZATION
Visualizing laser interaction with metals, hundreds of millions of primitives on DGX-1
Developed by Benjamin Hernandez, OLCF-ORNL
Exploratory Visualization of Petascale Particle Data in NVIDIA DGX-1Tuesday, 3:30 PM – Room 212B
Simulation: OLCF INCITE 2017 "Petascale Simulations of Short Pulse Laser Interaction with Metals" PI Leonid Zhigilei, University of Virginia
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NVIDIA: VRWORKS AUDIO
Sound waves reflect off of the environment
Path traced audio
NVIDIA VRWORKS AUDIO - Improving VR Immersion with acoustic fidelity
Thursday, 11:00 AM – Room 230B
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BUNGIE: LIGHT BAKING FOR GAMES
Light and occlusion baking is a major bottleneck in game design
Workflow-changing speedups by switching from CPU render farms to OptiX
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LIGHTMASSLight baking in Unreal Engine 4
Total Time on Titan X
CPU 1638sGPU 1X 426sGPU 2X 298s
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ADVANCED SAMPLESMaintained on Github
A collection of larger, more sophisticated sample applications than the ones that come with the SDK
Available at:
https://github.com/nvpro-samples/optix_advanced_samples
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FEATURE OUTLOOK
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PERFORMANCEMOTION BLURSEPARATE
COMPILATION
UNDER DEVELOPMENT
Shorter per-shadercompile times
Fast incremental addition and removal of programs
Overall speedup through parallel compilation
Performance is always a focus
Tackling some big ticket ideas over the next ~year
Transform and deformation blur
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THANK YOU!
Related Talks:
S7185 - LEVERAGING NVRTC RUNTIME COMPILATION FOR DYNAMICALLY BUILDING OPTIX SHADERS FROM MDL MATERIALS
S7454 - NVIDIA ADVANCED RENDERING
S7452 - CUTTING EDGE OPTIX RAY TRACING TECHNIQUES FOR VISUALIZATION OF BIOMOLECULAR AND CELLULAR SIMULATIONS IN VMD
S7175 - EXPLORATORY VISUALIZATION OF PETASCALE PARTICLE DATA IN NVIDIA DGX-1
S7400 - GPU-CLOUD PHOTOREALISTIC RENDERING FOR THE NEXT GENERATION OF CLOUD CAD TOOLS
H7106 - PHYSICALLY BASED RAY TRACING WITH OPTIX
S7391 - TURBOCHARGING VMD MOLECULAR VISUALIZATIONS WITH STATE-OF-THE-ART RENDERING AND VR TECHNOLOGIES
S7424 - INTRODUCTION AND TECHNIQUES WITH NVIDIA GVDB VOXELS
S7135 - NVIDIA VRWORKS AUDIO - IMPROVING VR IMMERSION WITH ACOUSTIC FIDELITY