lecturer athanasios nikolaidisteachers.cm.ihu.gr/nikolaid/cgma_intro.pdf · iain e.g. richardson,...

Lecturer Athanasios Nikolaidis

Computer Graphics: Graphics primitives 2D viewing and clipping 2D and 3D transformations Curves and surfaces Rendering and ray tracing Illumination models Shading models Texture mapping Computer animation

Multimedia Applications: Coding of audio-visual objects (MPEG-4) Multimedia content description interface

(MPEG-7) Multimedia information retrieval Multimedia framework (MPEG-21) Digital rights management

Peter Shirley, Steve Marschner, Fundamentals of Computer Graphics, CRC Press, 2009.

Shalini Govil-Pai, Principles of Computer Graphics: Theory and Practice Using OpenGL and Maya®, Springer, 2004.

David Salomon, Curves and Surfaces for Computer Graphics, Springer, 2006.

Iain E.G. Richardson, H.264 and MPEG-4 Video Compression: Video Coding for Next-generation Multimedia, Wiley, 2003.

Introduction to MPEG 7: Multimedia Content Description Interface, edited by B.S. Manjunath, Philippe Salembier and Thomas Sikora, Wiley, 2002.

The MPEG-21 Book, edited by Ian S. Burnett, Fernando Pereira, Rik Van de Walle and Rob Koenen, Wiley, 2006.

Synthetic images (images created using computers)

Digital “illustration of life”

Pixar’s first film, (“Luxo Jr.”, 1986)

Creation of an image

Movies Games Simulation CAD-CAM Architecture Virtual Reality Visualization Medical Imaging

Parallel to the history of computers: Pen plotters Simple displays using A/D converters

Wireframe graphics: Drawing only lines

Sketchpad A PhD at MIT (Ivan Sutherland, 1963) Predecessor to GUI, OOP

Raster graphics: Image as an array of picture elements (pixels) contained

in the frame buffer Not just lines anymore: filled shapes

Realistic graphics

smooth shading environment mapping bump mapping

OpenGL (API by SGI) Computer-generated full length movies (Toy Story)

Hardware with more features (texture mapping, blending, stencil buffers, etc.)

Photorealism Graphics cards for PCs (NVIDIA, ATI, etc.) with GPUs Game boxes and players determine market directions Software used on industrial level (Maya, Lightwave, etc.) Programmable pipelines

OpenGL (SGI) Direct3D (Microsoft) RenderMan Interface Specification (Pixar)

Modeling: mathematical representation of objects

Rendering: turning models into images Animation: the above plus movement

(change in time)

The programmer’s point of view: Specify geometric objects Describe their properties Define how they should be viewed Move either camera or objects around for

animation

The process of converting a set of 3D primitives to a corresponding set of 2D pixels to be displayed as output (using graphics hardware)

It is not efficient to render whole curves and surfaces directly

Basic geometric objects handled by graphics hardware. Can be points, line segments, circles, polygons, etc.

(most usual: triangles). More complex objects can be constructed based on

primitives.

RGB Color Texture Pattern

Ambient: same at every point on the surface Diffuse: scattered light independent of

angle (rough)

Specular: dependent on angle (shiny)

Most common are point sources

Rotation Translation Scaling

An object can be viewed from different angles:

Reproduce the effect of taking a photograph

Objects farther away are smaller in size Lines from each point on the image are drawn through

the center of the camera lens (the center of projection (COP)).

Camera positioning just results in more transformations on the objects: Transformations that position the object relative to the

camera Handled in the transformation process in the pipeline

up COP eye

What is visible on the screen?

If we draw objects directly, our screen will be a “mess”. Remove hidden surfaces.

Transforms pixel values in world coordinates to pixel values in screen coordinates

Delicate 3D models Perspective Hidden surface removal Shading (lighting & reflection) Shadow Detailed textures and normals