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- 1. INTRODUCTION TO 3D Michael Heron
- 2. INTRODUCTION For the next three weeks we will be talking about 3D graphics. Specifically, 3D graphics using the open source blender package. Module will concentrate on technical content. I have absolutely no artistic skill in the slightest. Seriously. Content time broken up into: Two lectures One tutorial One lab prep Four hour lab slot
- 3. GRAPHICS Graphical images on a computer monitor are made up of 2D arrays of pixels. The number of pixels in that array is dependant on the system’s resolution. Pixels represent a single element of an image. Represented by a colour code. Pixels have a depth. Represents the expressive palette of colours. 8 bit depth represents 256 colours 24 bit represents 16.8 million colours
- 4. COLOUR REPRESENTATION Colours are usually represented by an RGB value. An array of three digits corresponding to the blend of colours. An RGB value of {0,0,0} represents white. An RGB value of {255,255,255} represents black. Other colours made up of points in-between.
- 5. 4-BIT COLOUR
- 6. 8-BIT COLOUR PALETTE © Lucasarts, 1990
- 7. 24-BIT COLOUR PALETTE © Lucasarts, 2009
- 8. DISPLAYING GRAPHICAL INFORMATION Graphics are displayed on a computer monitor using rasters. Lines of pixels. CRT monitors make use of electron guns to display images on the screen. Three guns (red, green, blue) Guns fire beams at the phosphor coating on the inside of the monitor. This occurs many times per second. Governed by the monitor’s refresh rate.
- 9. DISPLAYING GRAPHICAL INFORMATION An LCD works somewhat differently. A backlight is used to create light This light passes through two substrates of polarised glass. While this is happening, an electrical current causes the crystals within the substrates to align. The combination of these substrates allows for the desired colours to appear at the appropriate point. There are other ways too Not important at this time.
- 10. REPRESENTING GRAPHICS (2D) Two main way of representing graphics in a computer. Rasters, comprised of arrays of pixels. Vectors, comprised of collections of objects expressed as mathematical formulae. Rasters used to represent photographs and other such bitmaps. Vectors used to represent more asbtract models.
- 11. REPRESENTING GRAPHICS (3D) In three dimensions, vectors are used almost exclusively for representing shapes. Images built up of collections of vertices, points, and polygons.
- 12. DIFFERENCES IN REPRESENTATION 2D Images Raster Permits great amounts of detail but no representation of relationship between objects. Substantial file size Vector Permits relationship of objects. Minimal details permitted Difficult to represent details using basic shapes Several trade offs Processing Power Realism Modifiability Expressive Potential.
- 13. 3D GRAPHICS Complex 3D scenes can be created as 2D images. Often done using ray-tracing or other technologies. Not real-time Goal of 3D graphics is to permit photorealistic representations of complex spatial topographies. Difficult task Requires much investment in building environments and objects within them Many applications require real-time rendering. Games
- 14. PHOTOREALISM 3D Graphics seeks to achieve photrealism by: Vector representation of 3D Objects Texturing of 3D objects in materials Interaction of light on objects Shadows Reflections Colour Glare Photorealism is important for many contexts. Simulation, entertainment, research, medical teaching
- 15. 3D ON A COMPUTER Not possible to show 3D images on a computer. Monitor is an inherently 2D device. Techniques are used to simulate the appearance of three dimensions. Use of perspective, layering, projection of a plane onto a fixed view. Many different interacting parts.
- 16. 3D MODELLING 3D Modelling is a multi-stage process. Representation Build a model of 3D Objects Shapes Surface textures Sometimes using bitmaps. Rendering Geometric translations Projection to 2D Light representation
- 17. THE CARTESIAN PLANE
- 18. SIMPLE 3D OBJECT (x1,y1,z1) (x2,y2,z2) (x3,y3,z3) (x4,y4,z4) (x5,y5,z5) (x6,y6,z6) (x7,y7,z7)(x8,y8,z8) © Glenn Rowe
- 19. MORE COMPLEX REPRESENTATIONS http://www.fallingpixel.com/3d-models/13227
- 20. 3D REPRESENTATIONS Complex shapes represented by polygons Triangles and Rectangles mostly Number of polygons defines the accuracy of the representation http://www.nvnews.net/reviews/evolva_preview.shtml
- 21. TRANSFORMATIONS Transformations used in 3D to manipulate images. Three main transformations used in Blender. Grab (translate) Used to move shapes around fixed axis Rotate Used to rotate shapes around a fixed axis Scale Used to scale shapes up or down Underlying representation done using matrix manipulation.
- 22. PROJECTION Projection is the process that transforms 3D objects onto a 2D plane. Three co-ordinate models. Local, defines the shape’s vertexes World space, defines the shape in relation to other shapes. Viewing space, defines the location and size of the shape when displayed on the monitor. Process turns {x,y,z} into just {x,y}
- 23. PROJECTION STYLES Parallel Projection Shows relationship between objects Not realistic View plane 3D object
- 24. PROJECTION STYLES Perspective Projection Represents objects more realistically by converging vertexes at a point. Foreshortening permits perspective. View plane 3D object Centre of projection
- 25. PROJECTION Both assume a camera location. The camera defines our view on the world. To change the view of an object, we can: Move the camera Move the object. Must get our heads around a viewport that has no fixed representation in the world space.
- 26. SUMMARY Next three weeks about 3D graphics. Using Blender. 3D Graphics consist of Representation of objects Representation of a world Representation of a view port Rendering Complex transforms applied to turn 3D representation into 2D view.

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