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.
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
20. 3D REPRESENTATIONS
Complex shapes represented by polygons
Triangles and Rectangles mostly
Number of polygons defines the accuracy of the
representation
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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.