csc 220 3d computer graphics fall 2003 l.
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CSC 220 3D Computer Graphics Fall 2003. Graphics Hardware. Text Mode – Characters (2K bytes) Graphics Modes – Pixels (millions of bytes) x-y coordinate system Raster Scan with Frame Buffer (aliasing ) Vector Scan with Display List. Color for Computer Graphics.

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graphics hardware
Graphics Hardware
  • Text Mode – Characters (2K bytes)
  • Graphics Modes – Pixels (millions of bytes)
  • x-y coordinate system
  • Raster Scan with Frame Buffer (aliasing)
  • Vector Scan with Display List
color for computer graphics
Color for Computer Graphics
  • Red, Green, Blue phosphors and shadow mask
  • VGA – 640 x 480 with 16 colors
  • VGA – 320 x 200 with 256 colors, using the

Color LookUp Table (CLUT) – 8 bits / pixel is

256 colors at one time, but 262,144 colors in palette

  • SVGA with True Color – 800 x 600 (or more), using

24 bits / pixel – millions of colors simultaneously

graphics software
Graphics Software
  • BASIC is an exception
  • API’s, or libraries

Borland Graphical Interface (BGI)

Graphical Kernel System (GKS)


graphics file formats
Graphics File Formats
  • GIF
  • JPEG
  • BMP
  • TIFF
  • Targa
the graphics pipeline
The Graphics Pipeline
  • Modeling – geometry of an object
  • Viewing – how the object appears

hidden surfaces

synthetic camera

  • Rendering – realism and more





modeling techniques
Modeling Techniques
  • Polygons (Triangles)
  • Splines (NURBS)
  • Constructive Solid Geometry (CSG)
  • Fractals

teddy a modeling applet
Teddy – a Modeling Applet
  • Simple and quick
  • For rough models instantly
  • Spherical topology
  • Operations





  • A tool for visual literacy
  • Can display 500,000 combinations of images rendered by various methods
  • Can be used in two ways

explore rendering effects

self-test rendering effects

  • Contains POV-Ray files also
some visual cues
Some Visual Cues
  • Visibility
  • Shadows
  • Reflections
  • Refraction
surface algorithms
Surface Algorithms
  • Visibility

wireframe – ambiguity

hidden lines / surfaces

  • Rendering techniques (2 of many)


ray tracing

some minimal mathematics
Some Minimal Mathematics
  • 3D coordinates – x,y,z as LHS
  • Vectors – direction and magnitude
  • Normal vector to a surface
  • Culling back faces
the z buffer method
The Z-buffer Method
  • Along with frame buffer have a z-buffer:

Frame buffer holds color value for the pixel

Z-buffer holds z value for the pixel location

  • Scan each surface in succession. If z value for this location on this surface is less than value in z-buffer, replace color in frame buffer and update value in z-buffer
  • Most common rendering method, often with special hardware
pov ray
  • No modeling, uses Scene Description Language (SDL)
  • Does viewing and rendering
  • No books in print, but excellent on-line documentation
  • Exercises from TERA text

render gold.pov, p.9

render room.pov, p.20

revise camera orientation of room, pp.21,22

specifying an image in sdl
Specifying an Image in SDL
  • Objects

Simple shapes

CSG objects

Advanced shapes

  • Transformations
  • Texture
  • Camera
  • Lighting
simple shapes
Simple Shapes
  • Spheres
  • Boxes
  • Cones
  • Cylinders
  • Planes
constructive solid geometry
Constructive Solid Geometry
  • Union
  • Intersection
  • Difference
  • Merge
transformation of coordinates
Transformation of Coordinates
  • Affine transformations




  • Composition of affine transformations
  • Properties of affine transformations

straight lines stay straight

parallel lines stay parallel

angles do NOT stay fixed, except for rigid transformations (no scaling)

z buffer shading
Z-Buffer Shading
  • Constant Shading – color computed once for entire object
  • Faceted Shading – color computed once for each polygon
  • Gouraud Shading – color computed using vertex normal, then double interpolation of color values in the polygon
  • Phong Shading – double interpolation of vertex normals, then color value computed for each interpolated vector value in the polygon
lights in pov ray
Lights in POV-Ray
  • Point lights
  • Spotlights






  • Cylinder lights (same parameters as spotlight)
  • Area lights
  • Ambient lighting
reflected light
Reflected Light
  • When light strikes a surface, some colors are absorbed, and we see the colors that are reflected.
  • We deal with three types of reflections:

ambient reflected light

diffuse reflected light

specular reflected light (Phong illumination)

  • Computing the reflected values requires that vectors must be multiplied.
ray tracer shading
Ray Tracer Shading
  • Multiple reflections
  • Transparency
  • Refraction
  • Shadows
2d texture mapping
2D Texture Mapping
  • Map Types

planar – normal parallel to X, Y, or Z

cylindrical – rotation around X, Y, or Z

spherical – rotation around X, Y, or Z

box – normal parallel to X, Y, or Z

  • Problems




  • Bilateral symmetry and planar maps
3d texture mapping
3D Texture Mapping
  • Procedural – texture is function f(x,y,z)
  • Common textures are stripes, rings, ramps
  • Noise for realistic effects



use of higher order terms

eccentricity, tilt, and twist

  • Texture functions in POV-Ray for glass, metal, stone, and wood
viewing the synthetic camera
Viewing – the Synthetic Camera
  • World Coordinates (WC) – x,y,z

r is location of camera in WC

  • The View Plane – U,V,N

N is where camera is looking

V is up direction, orthogonal to N

U is 3rd axis, orthogonal to both N and V

light and its perception
Light and its Perception
  • In describing the effects of light we must take into account both physics and physiology.
  • The wavelength of visible light varies from 400 nanometers (violet) to 700 nanometers (red).
  • In describing the quality of light, we need three parameters:

hue – the dominant wavelength

intensity (physics) or brightness (physiology)

saturation – the purity of the hue

the human eye
The Human Eye
  • The eye has rods that are very sensitive to light versus dark (about 1 photon), and cones that are less sensitive to level (about 5 photons) but can distinguish colors.
  • There are cones sensitive to blue, to green, and to red. They are all in the fovea (1/4 mm), and are the basis of the tristimulus theory of vision.
  • Light which is a mixture of red and green looks just as yellow as does pure yellow light! The human visual system cannot detect overtones and harmonics as does the human auditory system.
the color cubes
The Color Cubes
  • The primaries for additive (emitted) color in computer graphics are red, green, and blue, yielding the RGB color cube.

red + green = yellow

red + blue = magenta

green + blue = cyan

  • The primaries for subtractive (reflected) color are cyan, magenta, and yellow, yielding the CMY color cube.

cyan ink absorbs red

magenta ink absorbs green

yellow ink absorbs blue

the hsv color system
The HSV Color System
  • It is difficult to predict what a given mixture of RGB levels will look like.
  • For such a purpose, it is easier to use the HSV coordinate system based upon Hue, Saturation, and Value.
  • This maps to a cone or a six-sided pyramid:

Hue is the angular location on the side wall

Saturation is the relative distance from the center line to the color point (purity)

Value is the height in the inverted cone

  • These can easily be thought of in more natural terms such as tints, shades, and tones.

When there are a limited number of color levels available in the output, we can trade spatial resolution for color resolution. Thus, there may be just 2 color levels (e.g. black or white). Take ‘super-pixels’ of size 2x2 or 3x3. Within a 2x2 block, there are 4 individual pixels that may or not be lit, for 5 levels of aggregate intensity in that super-pixel.

To the eye, the increased color gradation is well worth the loss in spatial resolution.

some advanced shapes
Some Advanced Shapes
  • Blobs for lumpy objects
  • Splines to fit to control points

approximation – Bezier curves

interpolation – many types of splines

piecewise polynomial sections (cubics)

smoothness, or continuity

  • NURBS – Non Uniform Rational BSplines
  • Non-uniform rational B-splines

non-uniform – spacing of control points

rational – a quotient (ratio) of polynomials

also knots where kinks are desired

  • NURBS are good for modeling curves

Just as important properties are maintained

with affine transformations, so are NURBS maintained under projective transformations

– so only control points need be transformed.

  • NURBS can model conic sections exactly!
the rhino interface
The Rhino Interface
  • Rhino is a modeling tool – has primitive shading and rendering capability
  • 3 Orthographic Viewports

top, front, right views are default

bottom, back, left views are also possible

  • 1 Perspective Viewport
  • 2 Toolbars, with flyouts
viewing in rhino
Viewing in Rhino
  • Parallel or perspective projection (each viewport)
  • Panning
  • Rotating
  • Zooming

zoom dynamic

zoom extents

zoom window

zoom selected

drawing lines
Drawing Lines
  • Line segments versus polylines
  • Coordinate systems

absolute cartesian 3,4

relative cartesian r3,4

absolute polar 5<60

relative polar r5<60

modeling aids
Modeling Aids
  • Snap to grid
  • Ortho
  • Object Snaps
  • Layers
  • Constraints

distance constraint 5

angle constraint <60

editing objects
Editing Objects
  • Split and Trim
  • Join and Explode
  • Fillet
  • Chamfer
  • Transforms




rhino geometry
Rhino Geometry
  • Points
  • Curves
  • Surfaces
  • Polysurfaces – blended surfaces
  • Solids – closed polysurfaces
creating curves
Creating Curves
  • Free-form

control points – Bezier curves

(for approximation)

interpolate points – spline curves

(for interpolation)


  • Conic sections
  • Polygons
creating surfaces
Creating Surfaces
  • From points
  • From curves
  • Extrusion
  • Lofting
  • Revolves
  • Rail sweeps
creating solids
Creating Solids
  • Box
  • Sphere
  • Cylinder
  • Tube
  • Cone
  • Ellipsoid
  • Torus
technical side of animation
Technical Side of Animation
  • The Storyboard
  • Keyframes
  • Inbetween frames

for shape (morphing)

for motion

  • Motion capture
  • Physical modeling
artistic side of animation
Artistic Side of Animation
  • Stretch and Squash
  • Timing
  • Anticipation
  • Staging
  • Slow In and Out
  • Emotion