advanced computer graphics spring 2014 k. h. ko school of mechatronics gwangju institute of science...

Advanced Computer Graphics Spring 2014

K. H. Ko

School of MechatronicsGwangju Institute of Science and Technology

2

Today’s Topics

Introduction Graphics Rendering Pipeline

3

Introduction

Game Engine Graphics side

Graphics Engine Physics side

Physics Engine

Physics Engine A library that encapsulates the implementation

of the low-level physics and provides high-level API for those applications that require enforcement of physical laws.

4

Introduction

Core System

Low-level system-Basic data structure

-File Handling

-Memory Management

-Etc.

Mathematics system-Basic Mathematics functions

-Vector & Matrix Algebra

-Quaternions

-Etc.

Object Management

Interface to System

5

Physics Engine Graphics Engine

Introduction

Core System

- Rendering system

-Collision Detection

-Physics system

-Etc.

Game Engine

6

Applications

Physics Engine Graphics Engine

Introduction

Core System

7Taken from the course notes by Tomas Akenine-Möller, Chalmers University of Technology

State-of-the-Art Real-Time Rendering2001

8

State-of-the-Art Real-Time Rendering2001

Taken from the course notes by Tomas Akenine-Möller, Chalmers University of Technology

9

Which one is a real photo,and which one is CG?


10

Complexity: 8 million triangles…


11

Photo-realistic Rendering…


12

Graphics Rendering Pipeline

The main function of the pipelineGenerate, or renderrender, a two-dimensional

image. Given a virtual camera, three-dimensional

objects, light sources, lighting models, textures and more.

The pipeline is the underlying tool for real time rendering.

13


Example

14


ArchitectureThree conceptual stages – the engine of

the rendering pipeline

Each of these stages is usually a pipeline in itself.

15


ArchitectureConceptual stages

Application, geometry and rasterizerFunctional stages

Has a certain task to perform But does not specify the way that task is

executed in the pipelinePipeline stages

It is executed simultaneously with all the other pipeline stages.

16


ArchitectureExample

The geometry stage may be divided into five functional stages.

But it is the implementation of a graphics system that determines its division into pipeline stages.

A given implementation may combine two functional stages into one pipeline stage.

While it divides another, more time-consuming, functional stage into several pipeline stages or parallelizes it.

17


ArchitectureDetermination of the rendering speed:

the update speed of the images, fps (frames per second)

The slowest of the pipeline stages

18


Application Stage (executed on CPU) Driven by the application and therefore

implemented in software. Collision detection, acceleration algorithms,

animations, force feedback, etc. The developer has full control over what

happens in the application stage. At the end of the application stage, the

geometry to be rendered is fed to the next stage.

Rendering primitives, i.e., points, lines, triangles, etc.

19


Application Stage (executed on CPU) Rendering Primitives.

Most important task is to send rendering primitives (e.g. triangles) to the graphics hardware

20


Geometry stageComputes what is to be drawn, how it

should be drawn and where it should be drawn.

Is responsible for the majority of the per-polygon operations or per-vertex operations.

Implemented either in software or in hardware.

Transforms, projections, lightings, etc.

21


Geometry stageFunctional stages: They form a single

pipeline stage.

It performs a very demanding task. Model and view transform, lighting and

shading, projection, clipping, screen mapping

22


Geometry stageModel and view transform

Model coordinates -> model transform -> world coordinate or world space

The world space is unique. All models exist in the same space.

Only the models that a camera sees are rendered.

The camera has a location in world space and a direction.

23



View transform : To facilitate projection and clipping, the camera and all the models are transformed with the view transform.

This transform makes the clipping and projection operations simpler and faster.

24



25


Geometry stageLighting and shading

In order to lend models a more realistic appearance, the scene can be equipped with one or more light sources.

Shading technique – The colors are given at the vertices of a triangle. Interpolation techniques are needed to cover the entire triangle.

Gouraud Shading, Phong Shading, etc.

26


Geometry stageLighting and shading

blue

red green

27


Geometry stageProjection

After lighting, rendering systems perform projection.

It transforms the view volume into a unit cube with its extreme points at (-1,-1,-1) and (1,1,1).

The unit cube is called the canonical view volume. Orthographic projection Perspective projection

28


Geometry stageProjection

29


Geometry stageClipping

Only the primitives wholly or partially inside the view volume need to be passed on to the rasterizer stage, which then draws them on the screen.

The primitives that are partially inside the view volume require clipping.

Due to the projection transformation, the clipping is done against the unit cube.

Consistency

30


Geometry stageClipping

31


Geometry stageScreen Mapping

The coordinates of the primitives from the previous stage are still three-dimensional.

The x and y coordinates of each primitive are transformed to form screen coordinates.

Window coordinates.

32


Geometry stageScreen Mapping

33


Rasterizer stage Draws (renders) an image with use of the data

that the previous stage generated. Given the transformed and projected vertices, colors

and texture coordinates, the goal of the rasterizer stage is to assign correct colors to the pixels to render an image correctly.

Rasterization or scan conversion. Per-pixel operations

Color buffer. It is responsible for resolving visibility.

Z-buffer (depth buffer) is used.

34


Rasterizer stage

Geometric Primitives Rasterized Primitives

35

ExampleOpenGL Rendering Pipeline

36

OpenGL Rendering Pipeline

Display ListsAll data (geometry or pixels) can be

saved in a display list for current or later use.

Cf. Immediate modeWhen a display list is executed, the

retained data is sent from the display list.

37


38


EvaluatorsAll geometric primitives are eventually

described by vertices.Evaluators provide a method for

deriving the vertices used to represent curves or surfaces.

Parametric curves and surfaces : evaluate vertices using the control points and basis functions.

39


40


Per-Vertex Operations They convert the vertices into primitives.

Vertex data transformation Texturing Lighting calculation etc.

Primitive Assembly Constructs complete geometric primitives

They are transformed and clipped vertices with related color, depth and sometimes texture-coordinate values and guidelines for rasterization.

41


42


Pixel Operations From system memory

Pixels are first unpacked into the proper number of components.

Next the data is scaled, biased and processed by a pixel map.

The results are clamped and then either written into texture memory or sent to the rasterization step.

From frame buffer If pixel data is read from the frame buffer

43


Pixel OperationsFrom frame buffer

If pixel data is read from the frame buffer, pixel-transfer operations (scale, bias, mapping and clamping) are performed.

Then, the results are packed into an appropriate format and returned to an array in system memory.

44


45


Texture Assembly Rasterization

The conversion of both geometric and pixel data into fragments.

Each fragment square corresponds to a pixel in the framebuffer.

Anti-aliasing are taken into consideration. Color and depth values are assigned for

each fragment square.

46


47


Fragment Operations1st Operation: texturing2nd Operation: fog calculation3rd Operation: blending, dithering,

logical operation, masking by a bitmask4th Operation: the thoroughly processed

fragment is drawn into the appropriate framebuffer.

48

Q & A?

advanced computer graphics spring 2014 k. h. ko school of mechatronics gwangju institute of science...

Documents