Introduction graphics
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This document provides an overview and outline of a computer graphics course. It discusses that the course will cover graphics programming, algorithms, data structures, color, geometry, modeling, rendering, and applications in animation, games, medical imaging, and scientific visualization. The graphics pipeline is reviewed as having application, geometry, and rasterization stages. Key graphics concepts like modeling transformations, lighting, shading, texture mapping, and anti-aliasing are also introduced. The first practical assignment involves rendering and shading a 3D teapot model.
Introduction graphics
- 2. What’s this course all about? 04/08/13 Lecture 1 2 We will cover… Graphics programming and algorithms Graphics data structures Colour Applied geometry, modelling and rendering
- 3. Computer Graphics is about animation (films) 04/08/13 Lecture 1 3 Major driving force now
- 4. Games are very important in Computer Graphics 04/08/13 Lecture 1 4
- 5. Medical Imaging is another driving force 04/08/13 Lecture 1 5
- 6. Computer Aided Design too 04/08/13 Lecture 1 6
- 7. Scientific Visualisation 04/08/13 Lecture 1 7 To view below and above our visual range
- 8. First Lecture • The graphics processes – What we will cover on this course • Some definitions – Fundamental units we use in these processes • First Practical 04/08/13 Lecture 1 8
- 9. Overview of the Course • Graphics Pipeline (Today) • Modelling – Surface / Curve modelling • (Local lighting effects) Illumination, lighting, shading, mirroring, shadowing • Rasterization (creating the image using the 3D scene) • Ray tracing • Global illumination • Curves and Surfaces 04/08/13 Lecture 1 9
- 10. Graphics/Rendering Pipeline • Graphics processes generally execute sequentially • Pipelining the process means dividing it into stages • Especially when rendering in real-time, different hardware resources are assigned for each stage 04/08/13 Lecture 1 10
- 11. Graphics / Rendering Pipeline • There are three stages – Application Stage – Geometry Stage – Rasterization Stage 04/08/13 Lecture 1 11
- 12. Application stage • Entirely done in software by the CPU • Read Data – the world geometry database, – User’s input by mice, trackballs, trackers, or sensing gloves • In response to the user’s input, the application stage change the view or scene 04/08/13 Lecture 1 12
- 13. Geometry Stage 04/08/13 Lecture 1 13 Model Transformation Modeling: shapes Shading: reflection and lighting Transformation: viewing Hidden Surface Elimination Rasterization Stage
- 14. Rasterization Stage 04/08/13 Lecture 1 14 Rasterization and Sampling Texture Mapping Image Composition Intensity and Colour Quantization Geometry Stage Framebuffer/Display
- 15. An example thro’ the pipeline… 04/08/13 Lecture 1 15 The scene we are trying to represent: Images courtesy of Picture Inc.
- 16. Geometry Pipeline 04/08/13 Lecture 1 16 Model Transformation Loaded 3D Models Shading: reflection and lighting Transformation: viewing Hidden Surface Elimination Imaging Pipeline
- 17. Preparing Shape Models 04/08/13 Lecture 1 17 Designed by polygons, parametric curves/surfaces, implicit surfaces and etc. Defined in its own coordinate system
- 18. Model Transformation 04/08/13 Lecture 1 18 Objects put into the scene by applying translation, scaling and rotation Linear transformation called homogeneous transformation is used The location of all the vertices are updated by this transformation
- 19. Perspective Projection 04/08/13 Lecture 1 19 We want to create a picture of the scene viewed from the camera We apply a perspective transformation to convert the 3D coordinates to 2D coordinates of the screen Objects far away appear smaller, closer objects appear bigger
- 20. Hidden Surface Removal 04/08/13 Lecture 1 20 Objects occluded by other objects must not be drawn
- 21. Shading 04/08/13 Lecture 1 21 Now we need to decide the colour of each pixels taking into account the object’s colour, lighting condition and the camera position Object point light source
- 22. Shading : Constant Shading - Ambient 04/08/13 Lecture 1 22 Objects colours by its own colour
- 23. Shading – Flat Shading 04/08/13 Lecture 1 23 Objects coloured based on its own colour and the lighting condition One colour for one face
- 24. Gouraud shading, no specular highlights 04/08/13 Lecture 1 24 Lighting calculation per vertex
- 25. Shapes by Polynomial Surfaces 04/08/13 Lecture 1 25
- 26. Specular highlights added 04/08/13 Lecture 1 26 Light perfectly reflected in a mirror-like way
- 27. Phong shading 04/08/13 Lecture 1 27
- 28. Next, the Imaging Pipeline 04/08/13 Lecture 1 28 Rasterization and Sampling Texture Mapping Image Composition Intensity and Colour Quantization Geometry Framebuffer/Display Pipeline
- 29. Rasterization • Converts the vertex information output by the geometry pipeline into pixel information needed by the video display • Aliasing: distortion artifacts produced when representing a high-resolution signal at a lower resolution. • Anti-aliasing : technique to remove aliasing 04/08/13 Lecture 1 29
- 30. Anti-aliasing 04/08/13 Lecture 1 30 Aliased polygons (jagged edges) Anti-aliased polygons
- 31. 04/08/13 Lecture 1 31 How is anti-aliasing done? Each pixel is subdivided (sub-sampled) in n regions, and each sub-pixel has a color; Compute the average color value
- 32. Texture mapping 04/08/13 Lecture 1 32
- 33. Other covered topics: Reflections, shadows & Bump mapping 04/08/13 Lecture 1 33
- 34. Other covered topics: Global Illumination 04/08/13 Lecture 1 34
- 36. Graphics Definitions • Point – a location in space, 2D or 3D – sometimes denotes one pixel • Line – straight path connecting two points – infinitesimal width, consistent density – beginning and end on points 04/08/13 Lecture 1 36
- 37. Graphics Definitions• Vertex – point in 3D • Edge – line in 3D connecting two vertices • Polygon/Face/Facet – arbitrary shape formed by connected vertices – fundamental unit of 3D computer graphics • Mesh – set of connected polygons forming a surface (or object) – :04/08/13 Lecture 1 37
- 38. Graphics Definitions • Rendering : process of generating an image from the model • Framebuffer : a video output device that drives a video display from a memory containing the color for every pixel 04/08/13 Lecture 1 38
- 39. Course support resources • Graphics course website • http://www.inf.ed.ac.uk/teaching/courses/ cg – lecture material, – lecture log with general summary and recommended reading, – Links to support material for lectures and projects, – Practical description and resources04/08/13 Lecture 1 39
- 40. First Practical • Write a program that renders an image of a teapot and outputs it into an image file • I prepared a demo program to load a 3D model and draw the edges • You update it so that the surface appears shaded • See the course website for the details 04/08/13 Lecture 1 40
- 41. Some notifications • 16 lectures in total • I need to visit Japan in the beginning of October so no lecture on 5th October • Need to attend conferences on 16th and 26th of November so no lectures there
- 42. Summary • The course is about algorithms, not applications • Lots of mathematics • Graphics execution is a pipelined approach • Basic definitions presented • Some support resources indicated 04/08/13 Lecture 1 42