CS 380 - GPU and GPGPU ProgrammingLecture 2: Introduction; GPU Architecture 1

Markus Hadwiger, KAUST

2

Reading Assignment #2 (until Feb. 17)

Read (required):• GLSL book, chapter 4 (The OpenGL Programmable Pipeline)

• GPU Gems 2 book, chapter 30 (The GeForce 6 Series GPU Architecture)available online:

http://download.nvidia.com/developer/GPU_Gems_2/GPU_Gems2_ch30.pdf

3

Example: Fluid Simulation and Rendering

• Compute advection of fluid– (Incompressible) Navier-Stokes solvers– Lattice Boltzmann Method (LBM)

• Discretized domain; stored in 2D/3D textures– Velocity, pressure– Dye, smoke density,

vorticity, …

• Updates in multi-passes

• Render current frame

Courtesy Mark Harris

4

Example: Volumetric Special Effects

• NVIDIA Demos– Smoke, water– Collision detection with

voxelized solid (Gargoyle)

• Ray-casting– Smoke: direct volume rendering– Water: level set / isosurface

Courtesy Keenan Crane

5

Example: Particle Simulation and Rendering

• NVIDIA Particle Demo

6

Example: Level-Set Computations

• Implicit surface represented by distance field

• The level-set PDE is solved to update the distance field

• Basic framework with a variety of applications

7

Example: Diffusion Filtering

De-noising• Original

• Linear isotropic

• Non-linear isotropic

• Non-linear anisotropic

8

Example: Linear Algebra Operators

Vector and matrix representation and operators• Early approach based on graphics primitives

• Now CUDA makes this much easier

• Linear systems solvers

Courtesy Krüger and Westermann

9

Example: GPU Data Structures

Glift: Generic, Efficient, Random-Access GPU Data Structures• “STL“ for GPUs

• Virtual memory management

Courtesy Lefohn et al.

10

What‘s in a GPU?

Lots of floating point processing power• Stream processing cores

different names:stream processors,CUDA cores, ...

• Was vector processing, now scalar cores!

Still lots of fixed graphics functionality• Attribute interpolation (per-vertex -> per-fragment)

• Rasterization (turning triangles into fragments/pixels)

• Texture samping and filtering

• Depth buffering (per-pixel visibility)

• Blending/compositing (semi-transparent geometry, ...)

• Frame buffers

What can the hardware do?

RasterizationDecomposition into fragmentsInterpolation of colorTexturing

Interpolation/Filtering Fragment Shading

Fragment OperationsDepth Test (Z-Test)Alpha Blending (Compositing)

Pixels

Graphics Pipeline

Vertices Primitives Fragments

GeometryProcessing

FragmentOperations

Scene Description Raster Image

Rasterization

Geometry Processing

Per-VertexLighting

Clipping,Perspect.Divide

PrimitiveAssemblyTransformation

Multiplication withModelview and

Projection Matrix

Per-VertexLocal Illumination

(Blinn/Phong)

GeometricPrimitives

(Points, LinesTriangles)

Primitives

Clip SpaceTo

Screen Space

Vertices

GeometryProcessing Rasterization Fragment

Operations

GeometryProcessing Rasterization Fragment

OperationsFragment

Operations

TextureFetch

TextureApplication

Polygon Rasterization

PrimitiveVertices

Decompositionof primitives

into fragments

Interpolation oftexture coordinates

Filtering oftexture color

Primitives Fragments

Rasterization

Combination ofprimary color with

texture color

Combination ofprimary color with

texture color

Fragment Operations

StencilTest

AlphaBlending

DepthTest

AlphaTest

Discard allfragments within

a certain alpha range

Discard afragment ifthe stencil buffer is set

Discard alloccludedfragments

GeometryProcessing Rasterization Fragment

Operations

Pixels

Graphics Pipeline

Vertices Primitives Fragments

GeometryProcessing

FragmentOperations

Scene Description Raster Image

RasterizationVertexShader

FragmentShader

Programmable Pipeline

17

Direct3D 10 Pipeline (~OpenGL 3.2)

New geometry shader stage:• Vertex -> geometry -> pixel shaders

• Stream output after geometry shader

Courtesy David Blythe, Microsoft

18

Direct3D 11 Pipeline (~OpenGL 4.0)

New tessellation stages• Hull shader

(OpenGL: tessellation control)

• Tessellator(OpenGL: tessellation primitive generator)

• Domain shader(OpenGL: tessellation evaluation)

• Trend of adding new stageslikely to continue...

• ... or full flexibility such asin Intel MIC (Larrabee) architecture?

Thank you.