游戏设计与开发. Outline. Game Programming Topics. Building A Game

Transcription

1 Outlie 游戏设计与开发 Real Time Requiremet A Coceptual Rederig Pipelie The Graphics Processig Uit (GPU) Example 技术篇 : 实时图形硬件 Game Programmig Topics Focus: Buildig game ad virtual world High-level uderstadig ad practical implemetatio experiece Reusable algorithms ad codig techiques Mai topics: real time rederig, game visual effects real time aimatio, game physics game desig others: artificial itelligece user iterface soud etwork Buildig A Game Backgroud Scee (e.g. sky, terrai) Static Objects Movemet of Objects Users Cotrol Collisio ad Respose Others 1

2 Game Loop The Game Loop (Mai Evet Loop) : How Fast Does my Game Loop Need to Ru? ANSWER: It depeds Visual displays: Hz or higher,90~120hz for VR display Head-trackig for HMDs: 60 Hz, but eve oly 2-5ms of latecy yields display lag, which ofte quickly causes users to lose their luch Haptic displays: much higher update rates ( Hz) Multitaskig / Multiprocessig: allows for differet update rates for differet types of output displays Mai requiremet: Real Time 3D Graphics 3D Graphics Software Tools High-level 3D graphics APIs: hardware-idepedet, trasparet access to 3D acceleratio Commoly-Used 3D Graphics APIs: OpeGL / GLUT Direct3D (part of DirectX, also icludig DirectDraw, DirectSoud, DirectIput, ad DirectPlay) Higher-level: Game Egie Graphics Hardware ad APIs GPU(Graphics Process Uit): Nvidia, AMD, Itel API: Microsoft: DirectX 9, DirectX 10, DirectX 11, OpeGL ARB: OpeGL 1.0, 2.0, 3.0, 4.0, 2

3 The Graphics Rederig Pipelie rederig pipelie or the pipelie The core compoet of real time graphics mai fuctio: geerate, or reder, a 2D image, give a virtual camera, 3D objects, light sources, lightig models, textures, ad more. Usig the pipelie Object (model, color, texture, material) Camera/view Light source The Basic Costructio High-Level Pipelie A coceptual rederig pipelie 3 coceptual stages: 3

4 Substages of Geometry Stage A pipelie cosists of several stages (N) ideally give a speedup of a factor of N Model Trasform model trasform:model space à world space View Trasform Purpose: place camera at the origi ad aim it to look i z, with y upward, x to the right Camera space (or eye space) right-had or left-had (API specific) Trasform Matrix Both are implemeted as 4x4 matrices Model Trasform View Trasform 4

5 Vertex Shadig Modelig object appearace: Object s materials Effects of light sources Shadig : Determiig the effect of a light o a material By computig a shadig equatio at poits o the object Per-vertex operatio or Per-pixel operatio Vertex Shadig Material data ca be stored at each vertex: Poits locatio A ormal A color Other umerical iformatio Shadig ca be performed i World space Model space Eye space Lightig Lightig i fixed-fuctio pipelie Light sources 5

6 Shadig Model Lightig Equatio i fixed-fuctio pipelie Shadig Model: Flat shadig, Gouraud shadig, Phog Shadig (ot i fixed) Projectio Clippig View volume à uit cube (-1,-1,-1) ad (1,1,1) Orthographic projectio, perspective projectio 6

7 Scree Mappig Substages of Rasterizer Stage Rasterizer: geometry à fragmets Cotiuous à discrete Rasterizer Stage Triagle Setup Compute the differetials ad other data for the triagle s surfaces used for sca coversio (ext stage) for iterpolatio of various shadig data produced by the geometry stage (ext stages) Performed by fixed-operatio hardware 7

8 Triagle Traversal Also called sca coversio Fid which samples or pixels are iside a triagle Check each pixel covered by the triagle Geerate a fragmet for the part of the pixel that overlaps the triagle Fragmet properties: depth, ad ay shadig data from the geometry stage: geerated usig data iterpolated amog the 3 triagle vertices Performed by fixed-operatio hardware Pixel Shadig Do ay per-pixel shadig computatios Iput: the iterpolated shadig data Output: oe or more colors to be passed to ext stage Executed by programmable GPU cores May techiques ca be employed here, e.g. Texturig: glue a image (1D,2D or 3D) oto the object Mergig Combie the fragmet color produced with the color curretly stored i color buffer color buffer : 2D array store color iformatio for each pixel (e.g. RGB) Not fully programmable, but highly cofigurable (eable SFXs) Also resolvig visibility: mostly depth test usig Z-buffer (same size as the color buffer, store depth value) Depth test:compare z-value before rederig to a pixel à update Z-buffer ad color buffer if closer Order-idepedet for opaque object, but eed back-to-frot for trasparet object (major weakess of Z-buffer) Merge stage: more buffers ad operatios Color buffer: colors Z-buffer: z-values (depth test) Alpha chael (color buffer): opacity values alpha test (==, >=, ) optioal before the depth test E.g. esure fully trasparet fragmets ot affect z-buffer Stecil buffer Record locatios of the redered primitive offscree buffer (typically 8 bits/pixel) Cotrol rederig ito the color buffer ad Z-buffer Powerful tool for SFXs: e.g. a circle widow Raster operatios (ROP) or bled operatios Frame buffer (all the buffers, or color + Z-buffer) Accumulatio buffer (images accumulated usig a set of ROP) e.g. motio blur, depth of field, atialiasig, soft shadows, Double bufferig: frot buffer & back buffer, swapped durig vertical retrace (avoid seeig ucompleted scree) 8

9 Various Pipelies Real-time rederig pipelies: decades of API ad GPU evolutio for real-time rederig applicatios fixed-fuctio pipelie (e.g. Nitedo s Wii, maybe the last) O-off cofiguratio Programmable GPUs (the moder way! ) Program exactly operatios i substages Offlie rederig pipelies: differet evolutio paths Film rederig: commoly micropolygo pipelies Academic, ad predictive rederig applicatios (Pre-Viz): ray tracig rederers Graphics Processig Uit (GPU) Evolutio of hardware graphics acceleratios: Started at the ed of the pipelie Worked back up the pipelie Hardware accelerator for higher-level applicatio-stage algorithms 1999, NVIDIA GeForce256, coied the term GPU Later evolutio: Cofigurable implemetatios à programmable shaders Vertex shader Fragmet shader Computed values are writte to multiple high-precisio buffers ad reused as vertex or texture data The Fixed-fuctio Graphics Pipelie Fixed-fuctio GPU Pipelie: Trasform Applicatio Vertices (3D) Trasform & Light Xformed, Lit Vertices (2D) Assemble Primitives Graphics State Screespace triagles (2D) Rasterize Fragmets (pre-pixels) Shade Fial Pixels (Color, Depth) Video Memory (Textures) Trasform & light (a.k.a. vertex processor) Trasform from world space to image space Compute per-vertex lightig CPU GPU Reder-to-texture A simplified fixed-fuctio graphics pipelie Courtesy Mark Harris 9

10 Fixed-fuctio GPU Pipelie: Rasterize Rasterizer Covert geometric rep. (vertex) to image rep. (fragmet) Fragmet = image fragmet Pixel + associated data: color, depth, stecil, etc. Iterpolate per-vertex quatities across pixels Fixed-fuctio GPU Pipelie: Shade Fragmet processors (multiple i parallel) Compute a color for each pixel Optioally read colors from textures (images) Courtesy Mark Harris The Moder Graphics Pipelie Graphics State Applicatio CPU Vertices (3D) Trasform Vertex Processor & Light Xformed, Lit Vertices (2D) Assemble Primitives Screespace triagles (2D) Rasterize GPU Fragmets (pre-pixels) Fragmet Shade Processor Fial Pixels (Color, Depth) Reder-to-texture Video Memory (Textures) Programmable vertex processor! Programmable pixel processor! 10

11 The Moder Graphics Pipelie Moder GPU implemetatio of rederig pipelie Graphics State Applicatio CPU Vertices (3D) Vertex Processor Xformed, Lit Vertices (2D) Programmable primitive assembly! Geometry Assemble Processor Primitives Screespace triagles (2D) Rasterize GPU Fragmets (pre-pixels) Fragmet Processor Fial Pixels (Color, Depth) Reder-to-texture Video Memory (Textures) More flexible memory access! gree : fully programmable yellow: cofigurable but ot programmable blue: completely fixed i their fuctio Vertex Shader (fully programmable) - Model ad View Trasform - Vertex Shadig - Projectio DirectX Shader Model Timelie Geometry shader (optioal) - (fully programmable) Operate o the vertices of a primitive (poit, lie, or triagle) Clippig, scree mappig, triagle setup, triagle traversal stages (fixed) Pixel Shadig - (fully programmable) Pixel shadig fuctio Merge Stage (highly cofigurable) Modifyig the color Z-buffer bled, stecil, ad other buffers 11

12 DirectX 5 / OpeGL 1.0 ad Before Hardwired pipelie Simple API iputs Small set of operatios Example Hardware NVIDIA RIVA 128 3dfx Voodoo S3 Virge Rigid data flow No read-back from frame buffer Released 1998 New Features DirectX 6 / OpeGL 1.2 Multitexturig (i OpeGL sice 1.3) Example Hardware NVIDIA RIVA TNT ATI Rage 128 DirectX 7 / OpeGL 1.3 Example: GeForce 256 (1999) Released 1999 More work outsourced to GPU Hardware Trasformatio ad Lightig (T&L, Direct3D oly) New Features Texture Compressio i OpeGL Example Hardware NVIDIA GeForce 256 ATI Radeo

13 DirectX 8 Addig Programmability Released 2000 Itroductio of Shader Model 1.1 Shaders are GPU-ru programs that maipulate Vertices or Pixels Eables a plethora of ew visual effects Adds programmable processors to the graphics pipelie Example Hardware: NVIDIA GeForce 3 ATI Radeo 9000 DirectX 9 Example: Geforce FX (2003) Released 2002 Much more geeral programmig paradigm Brachig Floatig poit fragmet programmig Shader Model 3.0 (i 9.0c, 2004) Big feature icremet Example Hardware NVIDIA GeForceFX (9.0) NVIDIA GeForce 6200 (9.0c) 13

14 OpeGL 2.0 Released 2005 OpeGL Shadig Laguage (GLSL) Vertex ad fragmet shaders GLSL ties shaders to OpeGL API Poit sprites Particle effects May more features DirectX 10 Released 2006 Aliged with Widows Vista New Features Geometry shaders; Streamig output; Arrays of surfaces ad resource views; State ecapsulatio Break with Past User mode drivers, eve for DX9 Drivers do ot implemet Shader Models <4.0 No more fixed fuctio (compiles legacy API calls to shaders) DirectX 11 Direct3d 11, Released 2009 Widows Vista(With Patch)/Widows 7 Shader Model 5.0 Tessellatio, Multithreaded rederig, Compute shaders, supported by hardware ad software ruig Direct3D 9/10/10.1 Direct3D 11.1 Widows 8, Stereoscopic 3D Rederig, GPGPU Direct3D 11.2 Widows 8.1, Tiled resources, GPGPU July 2015 Widows 10, Xbox Oe DirectX 12 reduce driver overhead: cosole-level efficiecy a lower level of hardware abstractio eablig future games to sigificatly improve multithreaded scalig ad (decrease) CPU utilizatio claimed to be better tha DirectX 11: 50-70% faster >50% reductio i power cosumptio 14

15 Uified Shader Desig Commo Shader Core Virtual Machie Rederig pipelie o loger visible i hardware Uified shader cores process both vertices ad pixels Shader Virtual Machie 15

16 Impact of Uified Shaders Programmable Shader Stage Commo-shader core (API) (after DX10) Vertex, pixel ad geometry shaders share a programmig model Fuctioal descriptio see by the applicatio programmer Uified shaders (GPU architecture) A GPU architecture that maps well to the commo-shader core Programmig model: Shaders are programmed usig C-like shadig laguages (e.g. Cg, HLSL, GLSL) DirectX 10 16

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19 DirectX 11 DirectX 10 DirectX 11 19