3 rendering pipeline
3D游戏程序设计之Quake综述
3D引擎的核心－渲染: rendering pipeline
Graphics rendering pipeline
流水线的主要功能是根据给定的虚拟摄像机、三维物体、光 源、光照模型、纹理等绘制一幅二维图像
主要处理大部分多边形和顶点操作
Model & view Transform
Lighting
Projection
Clipping
Screen Mapping
几何层可进一步细分为上述功能层
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3D引擎的核心－渲染: Rasterizer Stage(光栅化层)
目的：计算每个象素的颜色 处理Per-pixel operations 每个象素的信息存在颜色缓存(color buffer) 采用双buffer技术：绘制在back buffer进行，当绘制完
预处理每个表面光照，并生成level文件
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Id Tech
Id Tech3
2005年Id公开了QuakeIII的所有源码(游戏引擎,Level编辑器,机器人), 其代码中的 注释极为详细
/*
==============
VM_Call
Upon a system call, the stack will look like:
采用了Gouraud shading high-level shader language and a method for rendering
volumetric fog
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Id Tech
Id Tech4
Doom3 Engine, renderer部分被重写了 编程语言使用C++， 而不是 C 主要技术特点
unity3d 虚拟 场景 相机 camera 渲染原理
unity3d 虚拟场景相机 camera 渲染原理Unity3D 虚拟场景相机(Camera)渲染原理Unity3D是一款跨平台的游戏开发引擎，它提供了虚拟场景的渲染功能来呈现三维游戏和应用程序。
相机(Camera)是Unity3D中非常重要的一个组件，它负责捕捉场景中的元素并将其渲染到屏幕上。
在本文中，我们将探讨Unity3D虚拟场景相机的渲染原理。
1. 渲染管线(Rendering Pipeline)Unity3D的渲染过程通过渲染管线来完成，渲染管线由一系列的阶段组成。
主要阶段包括几何阶段(Geometry Stage)和光照阶段(Lighting Stage)。
相机(Camera)在几何阶段中将场景的元素转换为屏幕空间位置，并在光照阶段中将光照信息应用于场景中的元素。
2. 视图矩阵(View Matrix)和投影矩阵(Projection Matrix)相机(Camera)用视图矩阵和投影矩阵来定义其在场景中的位置和视角。
视图矩阵定义相机的位置和方向，将场景中的元素从世界空间转换到相机空间。
投影矩阵定义相机的投影方式，如透视投影或正交投影，将相机空间的元素投影到屏幕空间。
3. 渲染纹理(Render Textures)在渲染过程中，相机(Camera)通常会将渲染结果渲染到一个渲染纹理(Render Texture)上。
渲染纹理可以是屏幕大小的纹理，也可以是自定义大小的纹理。
通过渲染纹理，我们可以在屏幕上显示相机视角的渲染结果，或者将其作为输入传递给其他相机(Camera)。
4. 渲染层级(Render Layers)Unity3D中的相机(Camera)可以通过设置渲染层级(Render Layers)来决定其捕捉哪些物体。
每个游戏对象都可以设置所处的渲染层级，相机(Camera)可以选择性地渲染特定的渲染层级，从而实现场景的分层渲染。
这可以提高游戏的性能和渲染效果。
5. 深度缓冲(Depth Buffer)深度缓冲(Depth Buffer)是一种用于存储场景中元素的深度信息的缓冲区。
GPU性能评测指标
GPU性能评测指标GPU是图形处理器，也被称为显卡，是计算机中的一种重要硬件组件。
GPU的性能评测指标主要包括性能参数和功耗参数两个方面。
首先是性能参数。
1. 像素填充率（Pixel Fill Rate）：表示GPU每秒钟可以生成的像素数。
像素填充率越高，表示GPU在处理图像时的速度越快，可以更快地渲染图像。
2. 纹理填充率（Texture Fill Rate）：表示GPU每秒钟可以处理的纹理数量。
高纹理填充率意味着GPU可以更快地加载和渲染纹理图像，提高图像质量和细节。
3. 浮点运算性能（Floating Point Performance）：表示GPU执行浮点运算的能力。
浮点运算是GPU处理图像和计算的重要任务，高性能的浮点运算能力可以提高GPU在处理复杂计算任务时的效率。
4. 带宽（Bandwidth）：表示GPU内存和GPU核心之间的数据传输速度。
高带宽可以降低GPU内部数据传输的延迟，提高数据读写和处理的效率。
5. 渲染管线性能（Rendering Pipeline Performance）：表示GPU在执行渲染任务时的性能。
渲染管线性能包括几何处理、图元处理、光栅化、像素处理等多个环节，综合考虑了GPU在处理图像时的各个方面的性能。
然后是功耗参数。
1. 功耗（Power Consumption）：表示GPU在工作状态下消耗的电功率。
功耗越低，表示GPU在运行时消耗的电能越少，可以减少硬件使用的能源，降低功耗的同时提高计算性能。
2. 散热（Heat Dissipation）：表示GPU在工作时产生的热量。
高性能的GPU通常会产生较高的热量，如果散热不好，就会导致GPU过热，影响性能甚至损坏硬件。
3. 效能（Efficiency）：表示GPU在给定性能水平下的能耗。
高效能的GPU可以在相同的性能水平下消耗更少的电能，提高硬件的能源利用效率。
4. 静音性（Silent）：表示GPU在工作时的噪音水平。
unity hdadditionalcameradata 使用方法
unity hdadditionalcameradata 使用方法
《Unity HDAdditionalCameraData 使用方法》是一款Unity中
的插件，用于给相机添加额外的数据，以增强相机的功能和效果。
使用步骤如下：
1. 在Unity的Asset Store中下载并导入HD渲染管线（High Definition Render Pipeline）插件。
2. 创建一个新的相机对象，或者选择已有的相机。
3. 在Inspector面板中，选择相机对象，然后点击添加组件按
钮（Add Component）。
4. 在搜索框中输入"HD Additional Camera Data"，然后选择该
组件。
5. 在Inspector面板中，可以看到多个可配置的选项，可以按
需进行设置。
- Additional Camera Data：勾选此选项以启用HDAdditionalCameraData。
- Rendering Path：选择渲染路径，例如Deferred、Forward等。
- Clear Color Mode：选择清除颜色的模式，例如Sky等。
- Enable Hardware Anti-Aliasing：勾选此选项以启用硬件抗锯齿。
6. 根据需要，可以进一步设置其他选项，如体积云（Volumetric Cloud）、背景（Background）等。
7. 点击Play按钮，预览相机的效果。
通过上述步骤，您可以使用《Unity HDAdditionalCameraData 使用方法》插件来增强Unity中相机的功能和效果。
3d_pipeline
ExtremeTech3D Pipeline TutorialJune13,2001By: Dave SalvatorIntroductionFrom the movie special effects that captivate us,to medical imaging to games and beyond,the impact that 3D graphics have made is nothing short of revolutionary.This technology,which took consumer PCs by storm about five years ago,has its roots in academia,and in the military.In fact,in some sense,the3D graphics we enjoy on our PCs today is a sort of"Peace Dividend,"since many professionals now working in the3D chip,film and game development industries cut their teeth designing military simulators.Entertainment aside,3D graphics in Computer Assisted Design(CAD)has also brought industrial design a quantum leap forward.Manufacturers can not only design and"build"their products without using a single piece of material,but can also leverage that3D model by interfacing with manufacturing machinery using Computer Assisted Manufacturing(CAM).But for most of us,3D graphics has made its biggest impact in the entertainment industries,both in film and in games,and its here that most of us became acquainted with the technology and jargon surrounding3D graphics.It is useful to note that not all rendering systems have the same goals in mind.Offline rendering systems, such as those used in CAD applications,stress accuracy over frame rate.Such models might be used to manufacture airplane parts,for instance.Real-time renderers,like game engines and simulators,tend to emphasize constant frame rate to keep animations smooth and fluid,and are willing to sacrifice both geometric and texture detail in order to do this.Some renderers are a kind of hybrid,like those used in the Toy Story movies.Artists and programmers using Pixar's Renderman technology create visually stunning scenes,but each frame of animation might take hours to render on a server"farm"--a group of computers to which the rendering work is distributed. These offline-rendered frames are then sequenced together at24frames per second(fps),the standard film rate,to produce the final cut of the film.With the rapid growth of consumer3D chips'rendering power,the line between"consumer3D"and "workstation3D"has blurred considerably.However,real-time game engines do make trade-offs to maintain frame rate,and some even have the ability to"throttle"features on and off if the frame rate dips below a certain level.In contrast,workstation3D can require advanced features not needed in today's3D games.The field of3D graphics is expansive and complex.Our goal is to present a series of fairly technical yet approachable articles on3D graphics technology.We'll start with the way3D graphics are created using a multi-step process called a3D pipeline.We'll walk down the3D pipeline,from the first triangle in a scene to the last pixel drawn.We will present some of the math involved in rendering a3D scene,though the treatment of3D algorithms will be introductory.(We list a good number of references at the end of this story if you want to dive deeper).In the Pipe,Five By FiveBecause of the sequential nature of3D graphics rendering,and because there are so many calculations to be done and volumes of data to be handled,the entire process is broken down into component steps, sometimes called stages.These stages are serialized into the aforementioned3D graphics pipeline.The huge amount of work involved in creating a scene has led3D rendering system designers(both hardware and software)to look for all possible ways to avoid doing unnecessary work.One designerquipped,"3D graphics is the art of cheating without getting caught."Translated,this means that one of the art-forms in3D graphics is to elegantly reduce visual detail in a scene so as to gain better performance,but do it in such a way that the viewer doesn't notice the loss of quality.Processor and memory bandwidth are precious commodities,so anything designers can do to conserve them benefits performance greatly.One quick example of this is culling,which tells the renderer,"If the view camera(the viewer's eye)can't see it, don't bother processing it and only worry about what the view camera can see."With the number of steps involved and their complexity,the ordering of these stages of the pipeline can vary between implementations.While we'll soon inspect the operations within these stages in much more detail,broadly described,the general ordering of a3D pipeline breaks down into four sections:Application/ Scene,Geometry,Triangle Setup,and Rasterization/Rendering.While the following outline of these sections may look daunting,by the time you're done reading this story,you'll be among an elite few who really understand how3D graphics works,and we think you'll want to get even deeper!3D Pipeline-High-Level Overview1.Application/SceneScene/Geometry database traversalMovement of objects,and aiming and movement of view cameraAnimated movement of object modelsDescription of the contents of the3D worldObject Visibility Check including possible Occlusion CullingSelect Level of Detail(LOD)2.GeometryTransforms(rotation,translation,scaling)Transform from Model Space to World Space(Direct3D)Transform from World Space to View SpaceView ProjectionTrivial Accept/Reject CullingBack-Face Culling(can also be done later in Screen Space)LightingPerspective Divide-Transform to Clip SpaceClippingTransform to Screen Space3.Triangle SetupBack-face Culling(or can be done in view space before lighting)Slope/Delta CalculationsScan-Line Conversion4.Rendering/RasterizationShadingTexturingFogAlpha Translucency TestsDepth BufferingAntialiasing(optional)DisplayWhere the Work Gets DoneWhile numerous high-level aspects of the3D world are managed by the application software at the application stage of the pipeline(which some argue isn't technically part of the3D pipeline),the last three major stages of the pipeline are often managed by an Application Programming Interface(API),such as SGI's OpenGL,Microsoft's Direct3D,or Pixar's Renderman.And graphics drivers and hardware are called by the APIs to performing many of the graphics operations in hardware.Graphics APIs actually abstract the application from the hardware,and vice versa,providing the application with true device independence.Thus,such APIs are often called Hardware Abstraction Layers(HALs).The goal of this design is pretty straightforward--application makers can write their program once to an API,and it will(should)run on any hardware whose drivers support that API.Conversely,hardware makers write their drivers up to the API,and in this way applications written to this API will(should)run on their hardware(See Figure1).The parenthetical"should's"are added because there are sometimes compatibility issues as a result of incorrect usages of the API(called violations),that might cause application dependence on particular hardware features,or incorrect implementation of API features in a hardware driver,resulting in incorrect or unexpected results.Figure1-3D API stackSpace InvadersBefore we dive into pipeline details,we need to first understand the high level view of how3D objects and3D worlds are defined and how objects are defined,placed,located,and manipulated in larger three-dimensional spaces,or even within their own boundaries.In a3D rendering system,multiple Cartesian coordinate systems(x-(left/right),y-(up/down)and z-axis(near/far))are used at different stages of the pipeline.While used for different though related purposes,each coordinate system provides a precise mathematical method to locate and represent objects in the space.And not surprisingly,each of these coordinate systems is referred to as a"space."Model of X-Y-Z Cartesian Coordinate systemObjects in the 3D scene and the scene itself are sequentially converted,or transformed,through five spaceswhen proceeding through the 3D pipeline.A brief overview of these spaces follows:Model Space:where each model is in its own coordinate system,whose origin is some point on the model,such as the right foot of a soccer player model.Also,the model will typically have a control point or"handle".To move the model,the 3D renderer only has to move the control point,because model spacecoordinates of the object remain constant relative to its control point.Additionally,by using that same"handle",the object can be rotated.World Space:where models are placed in the actual 3D world,in a unified world coordinate system.It turnsout that many 3D programs skip past world space and instead go directly to clip or view space.TheOpenGL API doesn't really have a world space.View Space (also called Camera Space):in this space,the view camera is positioned by the application(through the graphics API)at some point in the 3D world coordinate system,if it is being used.The worldspace coordinate system is then transformed (using matrix math that we'll explore later),such that thecamera (your eye point)is now at the origin of the coordinate system,looking straight down the z-axis intothe scene.If world space is bypassed,then the scene is transformed directly into view space,with thecamera similarly placed at the origin and looking straight down the z-axis.Whether z values are increasingor decreasing as you move forward away from the camera into the scene is up to the programmer,but fornow assume that z values are increasing as you look into the scene down the z-axis.Note that culling,back-face culling,and lighting operations can be done in view space.The view volume is actually created by a projection,which as the name suggests,"projects the scene"infront of the camera.In this sense,it's a kind of role reversal in that the camera now becomes a projector,and the scene's view volume is defined in relation to the camera.Think of the camera as a kind ofholographic projector,but instead of projecting a 3D image into air,it instead projects the 3D scene "into"your monitor.The shape of this view volume is either rectangular (called a parallel projection),or pyramidal(called a perspective projection),and this latter volume is called a view frustum (also commonly calledfrustrum,though frustum is the more currentdesignation).click on image for full viewThe view volume defines what the camera will see,but just as importantly,itdefines what the camera won't see,and in so doing,many objects models andparts of the world can be discarded,sparing both 3D chip cycles and memorybandwidth.The frustum actually looks like an pyramid with its top cut off.The top of the inverted pyramid projection isclosest to the camera's viewpoint and radiates outward.The top of the frustum is called the near (or front)clipping plane and the back is called the far (or back)clipping plane.The entire rendered 3D scene must fitbetween the near and far clipping planes,and also be bounded by the sides and top of the frustum.Iftriangles of the model (or parts of the world space)falls outside the frustum,they won't be processed.Similarly,if a triangle is partly inside and partly outside the frustrum the external portion will be clipped off atthe frustum boundary,and thus the term clipping.Though the view space frustum has clipping planes,clipping is actually performed when the frustum is transformed to clip space.Deeper Into SpaceClip Space:Similar to View Space,but the frustum is now "squished"into a unit cube,with the x and ycoordinates normalized to a range between –1and 1,and z is between 0and 1,which simplifies clippingcalculations.The"perspective divide"performs the normalization feat,by dividing all x,y,and z vertex coordinates by a special"w"value,which is a scaling factor that we'll soon discuss in more detail.The perspective divide makes nearer objects larger,and farther objects smaller as you would expect when viewing a scene in reality.Screen Space:where the3D image is converted into x and y2D screen coordinates for2D display.Note that z and w coordinates are still retained by the graphics systems for depth/Z-buffering(see Z-buffering section below)and back-face culling before the final render.Note that the conversion of the scene to pixels, called rasterization,has not yet occurred.Because so many of the conversions involved in transforming throughthese different spaces essentially are changing the frame of reference,it's easy to get confused.Part of what makes the3D pipeline confusingis that there isn't one"definitive"way to perform all of theseoperations,since researchers and programmers have discovereddifferent tricks and optimizations that work for them,and because thereare often multiple viable ways to solve a given3D/mathematicalproblem.But,in general,the space conversion process follows theorder we just described.To get an idea about how these different spaces interact,consider this example:Take several pieces of Lego,and snap them together to make some object.Think of the individual pieces of Lego as the object's edges,with vertices existing where the Legos interconnect(while Lego construction does not form triangles,the most popular primitive in3D modeling,but rather quadrilaterals,our example will still work).Placing the object in front of you,the origin of the model space coordinates could be the lower left near corner of the object,and all other model coordinates would be measured from there.The origin can actually be any part of the model,but the lower left near corner is often used.As you move this object around a room(the3D world space or view space,depending on the3D system),the Lego pieces'positions relative to one another remain constant(model space),although their coordinates change in relation to the room(world or view spaces).3D Pipeline Data FlowIn some sense,3D chips have become physical incarnations of the pipeline,where data flows"downstream" from stage to stage.It is useful to note that most operations in the application/scene stage and the early geometry stage of the pipeline are done per vertex,whereas culling and clipping is done per triangle,and rendering operations are done per putations in various stages of the pipeline can be overlapped, for improved performance.For example,because vertices and pixels are mutually independent of one another in both Direct3D and OpenGL,one triangle can be in the geometry stage while another is in the Rasterization stage.Furthermore,computations on two or more vertices in the Geometry stage and two or more pixels(from the same triangle)in the Rasterzation phase can be performed at the same time.Another advantage of pipelining is that because no data is passed from one vertex to another in the geometry stage or from one pixel to another in the rendering stage,chipmakers have been able to implement multiple pixel pipes and gain considerable performance boosts using parallel processing of these independent entities.It's also useful to note that the use of pipelining for real-time rendering,though it has many advantages,is not without downsides.For instance,once a triangle is sent down the pipeline,the programmer has pretty much waved goodbye to it.To get status or color/alpha information about that vertex once it's in the pipe is very expensive in terms of performance,and can cause pipeline stalls,a definite no-no.Pipeline Stages--The Deep Dive1.Application/Scene3D Pipeline-High-Level Overview1.Application/SceneScene/Geometry database traversalMovement of objects,and aiming and movement of view cameraAnimated movement of object modelsDescription of the contents of the 3D worldObject Visibility Check including possible Occlusion CullingSelect Level of Detail (LOD)2.Geometry3.Triangle Setup4.Rendering /Rasterization The 3D application itself could be considered the start of the 3D pipeline,though it's not truly part of thegraphics subsystem,but it begins the image generation process that results in the final scene or frame ofanimation.The application also positions the view camera,which is essentially your "eye"into the 3D world.Objects,both inanimate and animated are first represented in the application using geometric primitives,orbasic building blocks.Triangles are the most commonly used primitives.They are simple to utilize becausethree vertices always describe a plane,whereas polygons with four or more vertices may not reside in thesame plane.More sophisticated systems support what are called higher-order surfaces that are differenttypes of curved primitives,which we'll cover shortly.3D worlds and the objects in them are created in programs like 3D Studio Max,Maya,AutoDesk 3D Studio,Lightwave,and Softimage to name a few.These programs not only allow 3D artists to build models,but alsoto animate them.Models are first built using high triangle counts and can then be shaded and textured.Next,depending on the constraints of the rendering engine--off-line or real-time--artists can reduce thetriangle counts of these high-detail models to fit within a given performance budget.Objects are moved from frame to frame by the application,be it an offline renderer or a game engine.Theapplication traverses the geometry database to gather necessary object information (the geometry databaseincludes all the geometric primitives of the objects),and moves all objects that are going to change in thenext frame of animation.Appreciate that in a game engine for instance,the renderer doesn't have theplayground all to itself.The game engine must also tend to AI (artificial intelligence)processing,collisiondetection and physics,audio,and networking (if the game is being played in multiplayer mode over anetwork).All models have a default "pose",and in the case of models of humans,the default pose is called itsDaVinci pose,because this pose resembles DaVinci's famous Vitruvian Man.Once the application hasspecified the model's new "pose,"this model is now ready for the next processingstep.click on image for full viewThere's an operation that some applications do at this point,called "occlusionculling",a visibility test that determines whether an object is partially orcompletely occluded (covered)by some object in front of it.If it is,the occludedobject,or the part of it that is occluded is discarded.The cost savings in termsof calculations that would otherwise need to be performed in the pipeline can beconsiderable,particularly in a scene with high depth complexity,meaning thatobjects toward the back of the scene have several "layers"of objects in front ofthem,occluding them from the view camera.If these occluded objects can be discarded early,they won't have to be carriedany further into the pipeline,which saves unnecessary lighting,shading andtexturing calculations.For example,if you're in a game where it's you versusGodzilla,and the big guy is lurking behind a building you're walking toward,youcan't see him (sneaky devil).The game engine doesn't have to worry aboutdrawing the Godzilla model,since the building's model is in front of him,andthis can spare the hardware from having to render Godzilla in that frame of animation.A more important step is a simple visibility check on each object.This can be accomplished by determining ifthe object is in the view frustum (completely or partially).Some engines also try to determine whether anobject in the view frustum is completely occluded by another object.This is typically done using simpleconcepts like portals or visibility sets,especially for indoor worlds.These are two similar techniques that getimplemented in 3D game engines as a way to not have to draw parts of the 3D world that the camera won'tbe able to see.[Eberly,p.413]The original Quake used what were called potentially visible sets(PVS)that divided the world into smaller pieces.Essentially,if the game player was in a particular piece of the world, other areas would not be visible,and the game engine wouldn't have to process data for those parts of the world.Another workload-reduction trick that's a favorite among programmers is the use of bounding boxes.Say for instance you've got a10,000-triangle model of a killer rabbit,and rather than test each of the rabbit model's triangles,a programmer can encase the model in a bounding box,consisting of12triangles(two for each side of the six-sided box).They can then test culling conditions(based on the bounding box vertices instead of the rabbit's vertices)to see if the killer rabbit will be visible in the scene.Even before you might further reduce the number of vertices by designating those in the killer rabbit model that are shared(vertices of adjacent triangles can be shared,a concept we'll explore in more detail later),you've already reduced your total vertex count from30,000(killer rabbit)to36(bounding box)for this test.If the test indicates the bounding box is not visible in the scene,the killer rabbit model can be trivially rejected,you've just saved yourself a bunch of work.You Down With LOD?Another method for avoiding excessive work is what's called object Level of Detail,referred to as LOD.This technique is lossy,though given how it's typically used,the loss of model detail is often imperceptible. Object models are built using several discrete LOD levels.A good example is a jet fighter with a maximum LOD model using10,000triangles,and additional lower resolution LOD levels consisting of5,000,2,500, 1000and500triangles.The jet's distance to the view camera will dictate which LOD level gets used.If it's very near,the highest resolution LOD gets used,but if it's just barely visible and far from the view camera, the lowest resolution LOD model would be used,and for locations between the two,the other LOD levels would be used.LOD selection is always done by the application before it passes the object onto the pipeline for further processing.To determine which LOD to use,the application maps a simplified version of the object(often just the center point)to view space to determine the distance to the object.This operation occurs independently of the pipeline.The LOD must be known in order to determine which set of triangles(different LOD levels)to send to the pipeline..Geometric Parlor TricksGenerally speaking,a higher triangle count will produce a more realistic looking rmation about these triangles--their location in3D space,color,etc.--is stored in the descriptions of the vertices of each triangle.The aggregation of these vertices in the3D world is referred to as a scene database,which is the very same animal as the geometry database mentioned above.Curved areas of models,like tires on a car, require many triangles to approximate a smooth curve.The adverse effect of aggressively curtailing the number of vertices/triangles in a circle,for example,via an LOD reduction would be a"bumpy"circle,where you could see the vertices of each component triangle.If many more triangles represented the circle,it would look far smoother at its edge.Optimizations can be made to reduce the actual number of vertices sent down the pipeline without compromising the quality of the model,because connected triangles share vertices.Programmers can use connected triangle patterns called triangle strips and fans to reduce vertex count.For example:In the case of a strip of triangles,the simplest example would be a rectangle described by two right triangles,with a shared hypotenuse.Normally,two such triangles drawn separately would yield six vertices. But,with the two right triangles being connected,they form a simple triangle strip that can be described using four vertices,reducing the average number of vertices per triangle to two,rather than the original three.While this may not seem like much of reduction,the advantage grows as triangle(and resulting vertex)counts scale,and the average number of unique vertices per triangle moves toward one.[RTR,p. 234]Here's the formula for calculating the average number of vertices,given m triangles:1+2/mSo,in a strip with100triangles,the average number of vertices per triangle would be1.02,or about102 vertices total,which is a considerable savings compared to processing the300vertices of the individual triangles.In this example,we hit the maximum cost savings obtainable from the use of strips for m number of triangles,which is m+2vertices[RTR,p.239].These savings can really add up when you consider that it takes32bytes of data to describe the attributes(such as position,color,alpha,etc.)of a single vertex in Direct3D.Of course,the entire scene won't consist of strips and fans,but developers do look to use them where they can because of the associated cost savings.In the case of fans,a programmer might describe a semicircle using20triangles in a pie-slice arrangement. Normally this would consist of60vertices,but by describing this as a fan,the vertex count is reduced to22. The first triangle would consist of three vertices,but each additional triangle would need only one additional vertex,and the center of the fan has a single vertex shared by all triangles.Again the maximum savings possible using strips/fans is achieved.Another important advantage of strips and fans,is that they are a"non-lossy"type of data reduction, meaning no information or image quality is thrown away in order to get the data reduction and resulting speedup.Additionally,triangles presented to the hardware in strip or fan order improve vertex cache efficiency,which can boost geometry processing performance.Another tool available to programmers is the indexed triangle list,which can represent a large number of triangles,m,with m/2vertices,about twice the reduction of using strips or fans.This representational method is preferred by most hardware architectures.Curved Surfaces AheadRather than use numerous triangles to express a curved surface,3D artists and programmers have another tool at their disposal:higher-order surfaces.These are curved primitives that have more complex mathematical descriptions,but in some cases,this added complexity is still cheaper than describing an object with a multitude of triangles.These primitives have some pretty odd sounding names:parametric polynomials(called SPLINEs),non-uniform rational b-splines(NURBs),Beziers,parametric bicubic surfaces and n-patches.Because3D hardware best understands triangles,these curved surfaces defined at the application level are tessellated,or converted to triangles by the API runtime,the graphics card driver or the hardware for further handling through the3D pipeline.Improved performance is possible if the hardware tessellates the surface after it has been sent from the CPU to the3D card for transform and lighting(T&L) processing,placing less of a load on the AGP port,a potential bottleneck.2.Geometry3D Pipeline-High-Level Overview1.Application/Scene2.GeometryTransforms(rotation,translation,scaling)Transform from Model Space to World Space(Direct3D)Transform from World Space to View SpaceView ProjectionTrivial Accept/Reject Culling(or can be done later in Screen Space)Back-Face Culling(can also be done later in Screen Space)LightingPerspective Divide-Transform to Clip SpaceClipping。
显卡的设计和工作原理
显卡的设计和工作原理
显卡（Graphics Processing Unit，简称GPU）是计算机中用于处理图形和图像的重要组件。
它负责执行复杂的图形渲染、计算和显示任务。
下面是显卡的设计和工作原理的一些基本概念：
1. 处理器核心（Processing Cores）：显卡包含多个处理器核心，每个核心都可以执行并行的计算任务。
这些核心通常是基于多线程架构设计的，可以同时处理多个任务。
2. 图形内存（Graphics Memory）：显卡拥有自己的高速图形内存，用于存储图像数据、纹理、渲染缓冲区等。
这些数据在处理过程中频繁访问，高速图形内存可以提供快速的数据传输和存取。
3. 图像渲染管线（Graphics Rendering Pipeline）：显卡通过图像渲染管线来处理图形数据。
这个管线包含多个阶段，包括顶点处理、光栅化、片元处理等。
每个阶段都有特定的功能，如顶点处理阶段负责将3D模型的顶点转换为2D屏幕坐标。
4. 着色器（Shaders）：显卡的处理器核心包含多个着色器单元，如顶点着色器、像素着色器等。
着色器是一种程序，用于计算每个像素的颜色和其他属性。
它们可以执行复杂的计算，如光照、纹理映射和阴影等。
5. 显示输出：显卡将最终渲染的图像数据发送到显示器，显示器将其转换为可见的图像。
显卡通常支持多个显示输出接口，如HDMI、DisplayPort和DVI 等。
显卡的设计和工作原理非常复杂，上述只是一些基本概念。
现代显卡具有强大的计算能力，常用于游戏、计算机辅助设计、科学计算等领域。
gpu的基本概念
GPU的基本概念一、引言图形处理单元（Graphics Processing Unit，简称GPU）是一种专门在个人电脑、工作站、游戏机和一些移动设备上进行图像运算工作的微处理器。
它是显卡的“心脏”，与CPU类似，只不过GPU是专为执行复杂的数学和几何计算而设计的，这些计算是图形渲染所必需的。
本文将详细介绍GPU的基本概念，包括其历史、结构、工作原理等。
二、GPU的历史1960年代，计算机开始出现图形界面，但当时的处理能力非常有限。
1970年代，为了提高图形处理的效率，人们开始研发专门的图形处理硬件，即GPU。
1981年，NVIDIA公司发布了第一款GPU——NV1，标志着GPU时代的开始。
此后，GPU的发展经历了多个阶段，从最初的2D图形处理，到3D图形处理，再到现在的深度学习等领域，GPU的应用越来越广泛。
三、GPU的结构GPU主要由以下几个部分组成：1. 流处理器（Streaming Processor）：也被称为CUDA核心，是GPU进行计算的基本单位。
每个流处理器都能独立执行计算任务，因此，流处理器的数量直接影响GPU的计算能力。
2. 显存（Video RAM）：用于存储图形数据。
显存的速度和容量都对图形渲染有很大影响。
3. 纹理单元（Texture Unit）：用于处理纹理映射等相关操作。
4. 渲染管线（Rendering Pipeline）：包含了一系列的图形处理步骤，如顶点处理、光栅化、裁剪、混合等。
四、GPU的工作原理GPU的工作原理主要包括以下几个步骤：1. 接收命令：GPU首先接收到CPU发送过来的图形处理命令。
2. 分配任务：GPU将这些命令分配给不同的流处理器。
3. 执行任务：每个流处理器独立执行分配到的任务。
4. 返回结果：完成任务后，GPU将结果返回给CPU。
五、GPU与CPU相比1.并行计算：GPU的设计目标是高效执行并行计算任务，它通常拥有数百个或数千个处理单元，可以同时执行大量的计算操作。
3d 渲染 引擎 基础知识
3d 渲染引擎基础知识3D渲染引擎基础知识3D渲染引擎是一种用于生成逼真的3D图像或动画的软件，它可以将3D模型转化为可视化的图像或视频。
渲染引擎使用光照、材质、纹理等技术来模拟真实世界中的光线反射、折射和阴影等效果，从而呈现出逼真的场景。
下面是关于3D渲染引擎基础知识的相关参考内容：1. 3D渲染引擎工作原理3D渲染引擎通常分为四个主要阶段：几何处理、光栅化、着色和输出。
几何处理阶段将3D场景中的模型进行处理，包括变换、裁剪和顶点着色等。
光栅化阶段将3D模型划分为像素，以生成2D图像。
着色阶段通过对每个像素进行光照计算和材质贴图，决定像素的最终颜色。
输出阶段将最终的像素显示在屏幕上或输出为图像或视频文件。
2. 光照模型光照模型用于模拟真实世界中的光照效果。
常见的光照模型包括Lambert模型、Phong模型和Blinn-Phong模型等。
Lambert模型根据表面法线和光源方向计算出每个像素的漫反射光照强度。
Phong模型在漫反射光照的基础上添加了镜面反射光照，通过计算视线和反射光线之间的夹角来模拟物体的高光效果。
Blinn-Phong模型是Phong模型的一种改进，使用半程向量代替反射光线的方向向量，提高了效率。
3. 材质和纹理材质决定了物体表面的外观和反射特性。
常见的材质属性有漫反射、镜面反射和折射等。
漫反射材质根据入射光的方向和物体法线计算出漫反射光照强度。
镜面反射材质用于模拟物体表面的镜面反射效果，根据入射光的方向、视线和法线计算出镜面反射光照强度。
折射材质用于模拟光线从一个介质进入另一个介质时的折射效果，根据折射率和法线等参数计算出折射光线的方向。
4. 阴影效果阴影效果可以增加场景的真实感。
常见的阴影技术有阴影映射（Shadow Mapping）和环境光遮蔽（Ambient Occlusion）等。
阴影映射使用深度贴图记录每个像素到光源的最近距离，从而确定阴影的位置和强度。
环境光遮蔽通过计算物体表面各点到其他物体的遮蔽程度，来模拟光线的散射和吸收效果，使得物体表面的暗部更加真实。
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Dongfeng Liu School of Information Engineering Guangdong University of Technology Guangzhou, China
Outline
Coordinate systems in OSG; Coordinate Transforms; From 3D world to 2D image; Camera subclass;
Texturing
At this stage, basically what we do is „glue‟ the pixels from a texture onto the object.
1.坐标系统
对象坐标系(object coordinate system: OCS) x,y,z 世界坐标系(world coordinate system: WCS) X,Y,Z 相机坐标系(viewing coordinate system: VCS) n,u,v （n的方向是从视点指向center的方向） 投影坐标系(clipping coordinate system: CCS) X,Y,Z (规格化设备坐标系，坐标值-1~1之间) 窗口坐标系(device coordinate system: DCS) x,y,z (z:0~1,x,y以窗口左下角为坐标原点)
Rasterization
At this stage,we are concerned with things: Line drawing, polygon filling, Depth testing( determine what is closest to the viewer), texturing
4.视口变换 场景从投影坐标系到窗口坐标系的变换。 通过投影矩阵Mwindow来实现：
2.模型视点变换 场景从世界坐标系到相机坐标系的变换。 2.1模型变换 在WCS中改变物体的位置、姿态、或缩放 2.2视点变换 调整相机位置和方向，对场景进行取景 2.3模型视点矩阵 模型视点变换通过模型视点矩阵Mmodel-view 来实现：
3.投影变换 场景从相机坐标系到投影坐标系的变换。 通过投影矩阵MGet rid of anything that is not in the view frustum.
Screen Mapping
• All of the operations that we‟ve done above are still in 3D (X, Y, Z) coordinates. • We need to map these coordinates to the viewport dimensions. For example, we might be running a game at 1920×1080, so we have to convert all the geometric coordinates into pixel coordinates.
Model Transform
OCS MT WCS
View Transform
WCS VT VCS
Projection Transform
VCS PT CCS
Viewport Transform
CCS VT DCS
Rendering Pipeline
Some Concepts
Camera
• the “camera” you‟ve created in your 3D package isn‟t really a camera at all. • It just represents a view transformation.
Projection
• in computer graphics, we do this by defining what‟s called a “view frustum”. • With a view frustum, anything inside the volume of the frustum is drawn. Everything outside is excluded or “clipped”.
Coordinate systems in OSG
Z
Y
X
object coordinate system: OCS x,y,z world coordinate system: WCS X,Y,Z Viewing (camera) coordinate system: VCS
clipping coordinate system: CCS X,Y,Z (-1~1) device coordinate system: DCS x,y,z (z:0~1,x,y以窗口左下角为坐标原点)
Rasterization
A raster display, is basically a grid of pixels. Each pixel has color values assigned. A “frame buffer” stores the data for each pixel. To determine the state of each pixel in a screen: • At each pixel, what should be visible. • What color the pixel should be.