This document outlines the fundamental processes involved in creating a 3D image, including techniques for defining geometry through line mode and box mode. It describes the importance of polygonal representation, transformations, and texturing in building 3D models. Key concepts such as extrusion and the rich texturing system in Blender are emphasized as essential tools for creating and rendering detailed 3D objects.

1. CREATING A 3D IMAGE
Michael Heron

2. INTRODUCTION
 In this lecture we are going to look at the process
we go through in order to build a 3D image.
 At least in theory.
 Will need to wait until the lab before we do it For Reals.
 Two main techniques for doing this.
 Line Mode
 Box Mode

3. TERMINOLOGY
 Face
 A simple shape used to make up a more complex
shape.
 Also known as a polygon
 Vertex
 A corner point of a polygon
 Edge
 A line represented by two connected vertexes

4. CREATING A 3D OBJECT
 We need to do several things.
 Define the geometry of the shape.
 Apply transforms to set
 Location
 Scale
 Rotation
 Define surface details.
 Textures
 We do this for each object in a scene.
 We’ll talk about only one.

5. DEFINE THE GEOMETRY
 How do we define the geometry?
 We choose between two main ways.
 Or a hybrid of the two.
 First way is to draw each point in the shape.
 For large, complex shapes – extremely difficult.
 The more polygons we have, the more difficult this
becomes.
 This is the line mode of drawing shapes.
 There be dragons.

6. DEFINE THE GEOMETRY
 How do you sculpt an elephant?
 You take a block of marble, and chip away all the bits
that don’t look like an elephant.
 This is the Box Mode of drawing shapes.
 Start with an approximate shape.
 Usually one of the standard geometric principles.
 Manipulate it until it fits your needs.
 Or at least, closely approximates your needs.
 Recommended approach.

7. DEFINE THE GEOMETRY
 A third way is to make use of a representation of a
real object.
 Requires the use of specialised hard-ware
 Which you don’t have.
 The method you choose depends on
 The nature of the object
 Requirements of the model.
 A hybrid approach is usually the best
 Start with a rough shape, draw extensions to handle fine
detail work.

8. 3D REPRESENTATIONAL FORMS
 Several ways to represent 3D Geometry:
 Polygonal.
 Objects approximated by nets of polygons
 A polymesh
 Bicubic
 Objects represented by nets of curved patches.
 Constructive Solid Geometry
 Constructed from sets of basic geometric shapes
 Space subdivision
 Ray-tracing
 We focus primarily on polygonal today.
 Talk about the rest in the next lecture, or thereabouts.

9. SIMPLE POLYMESH
(x1,y1,z1) (x2,y2,z2)
(x3,y3,z3)
(x4,y4,z4)
(x5,y5,z5) (x6,y6,z6)
(x7,y7,z7)(x8,y8,z8)

10. SIMPLE POLYMESH – LOCAL CO-ORDINATES
(0,0,0) (50,0,0)
(50,0,50)(0,0,50)
(0,50,0) (50,50,0)
(50,50,50)

11. SIMPLE POLYMESH - REPRESENTATION
object surfaces polygons vertices

12. SIMPLE POLYMESH - REPRESENTATION
 Represented by a face-vertex mesh
 A list of faces represented by vertexes
 A list of the vertexes and what faces they are part of
 Co-ordinate space of each vertex.
 This provides a mathematical, context independent
representation of an object in its own local space.

13. FACE-VERTEX MESH

14. POLYMESH NOTES
 Shape is only an approximation for complex images.
 Can’t represent a circle.
 Can represent something that is almost a circle
 Level of approximation dictated by polygon count.
 Shading and other detailing approaches can help to hide
shape approximations.
 Ubiquitous representation.
 Graphics cards usually include specialised hardware for
rendering large numbers of polygons.

15. DRAWING AN OBJECT
 Begin with simple starting shape.
 Want to draw a head? Start with a sphere.
 Can add a sphere as a base shape in Blender
 Consider necessary transforms.
 Can do vertex, edge, and face manipulation on
polymesh shapes.
 Can apply basic transforms to part of a shape.
 Can also extrude.
 Used to extend a part of a shape.

16. DRAWING AN OBJECT
 Can also spin basic shapes:
http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Modelling_a_Mu
g_using_Spinning_and_Extrusion

17. DRAWING A SHAPE
 Blender provides many different modifiers to
change the basic structure of how you interact with
a shape.
 Mirror allows you to mirror modifications across a
shape.
 Subsurf makes a rough image much smoother and
more organic.
 Lots of these modifiers
 Experimentation is the key

18. MODIFIER - SUBSURF

19. MOLDING A SHAPE
 Back to the elephant.
 How do we turn a simple shape into what we actually want?
 Begin with a sphere
 Elephant body
 Select appropriate faces on that sphere.
 Extrude into legs
 Add another sphere
 The head
 Extrude a trunk
 Extrude a tail
 The rough work is handled using these kind of processes.

20. EXTRUSION
 Extrusion is one of the most powerful tools you
have available in blender.
 Pick a face, and extend it outwards or inwards.
 Used to raise and lower surfaces.
 Can be used to create entirely new surfaces.
 Used to create shapes where shapes did not
previously exist.
 For example, in the coffee cup.

21. EXTRUSION

22. TEXTURING
 Once you have a basic shape you want to make
use of, you can apply various textures to it.
 This changes the colour, and how it interacts with light
sources.
 A base blender scene has three elements.
 A light source (by default, the sun)
 A camera
 A shape

23. TEXTURING
 The texturing system in Blender is extremely rich.
 You can set how your object interacts with light
 You can set the specific kind of rendering to be done
 You can choose transparency and type of textures.
 Most of these will not be visible except in preview
until a scene is rendered.

24. TEXTURES
 Importantly, we can also make use of predefined
bitmaps for a texture.
 We can make use of our own images which get layered onto
the shapes we provide.
 We’ll see more of this later lectures and labs.
 It’s not a simple concept and easier to understand when
shown rather than simply described.
 Experimentation very important.
 Can’t even begin to cover what Blender makes available!

25. SUMMARY
 Polymeshes are the graphical representation must
used.
 We’ll talk about the rest later.
 3D Object created by:
 Representing geometry
 Applying transforms
 Applying textures
 Rendering