CS 470 WVU Final

right-handed coordinate system

+x - to the right +y - up +z - toward the viewer

modelview matrix

4x4 matrix defining any/all transformations to the CG model

Projection matrix

4x4 matrix defining how the model data will be projected to the viewport

Triangular matrix

A matrix containing data in the upper or lower half of the matrix (including diagonal)

Diagonal matrix

A matrix containing values on the main diagonal. All other values are zero

Matrix algebra properties

Associative (AB)C = A(BC) Distributive (A+B)C = AC + BC or C(A+B) = CA + CB Not commutative AB ≠ BA

near clipping plane

In a 3D model space a boundry in which objects are modeled closer to the viewpoint than that boundry and will not be rendered and therefore not seen in the view

for matrix multiplication the number of columns in the first matrix...

Must equal the number of rows in the second matrix

Screen Coordinates

Positions on a display device, often in terms of pixels

glPushMatrix()

Push the current matrix on the stack

2 Basic Color models

RGB (additive) & CMY (subtractive)

World Coordinate System

The coordinate system for the space that you are working in, the whole model space

scene graph

The representation of a computer graphics model or components of a model to identify the components and their hierarchical relationship in the model in the form of a graph

sketetal animation

To create an animation of an object moving like for example a person walking, defining that object in terms of rigging components such as upper leg, lower leg, foot, etc. and connections of these objects where these objects can move relative to each other

Matrix Transposition

To transpose a matrix is to turn rows into columns and columns into rows

8

What is the maximum number of lights allowed (at one time) in most implementations of OpenGL

viewing volume

What you can see (on the screen or in a window) is a box it has a left side, a right side, a top, a bottom, a front and a back

display list

a "container" for storing defined sets of graphic instructions that can be called and reused later

Frame buffer (or color buffer)

a buffer (array of memory) for storing model data for representation on a 2D display device

Z buffer

a construct that keeps track of whether a surface, part of a surface, and object or fragment is behind another surface, part of a surface, object or fragment and should no be rended in the projected display is known as a

Sample mode

a function call in program collects measure. Immediate, does not depend on trigger. Polling

Emissive light

a light in which the object is a light source.

Magnification

a portion of a texel must map to an entire pixel

Mipmaps

a set of successively smaller, lower resolution versions of a texture, reduction in powers of 2

Coloring

adds color to an object in a homogenous way

Lighting

adds color too, but models the effects of various lights on objects

purpose of double buffering is

allow the generation of a 2D projection by the application software, without interfering with the transfer of the 2D image to the screen

glRotatef(angle, x, y, z)

angle - the angle of the rotation x,y,z - a vector that defines the axis of rotation vector origin is the coordinate origin

glLoadIdentity()

clears the current transformation matrix

Diffuse light

comes from a specific position and travels in a specific direction

Object coordinate system

coordinates relative to respective object

Euclidean distance formula

d = sqrt((x2-x1)^2 + (y2-y1)^2))

glViewport(x, y, width, height)

defines a view port (a rectangle in the window where the image will be displayed

GL_SPOT_EXPONENT

defines the degree of fade in light intensity from the center point of the light to edge of the spot light area.

Emissive light

emits light (glows)

glFlush()

forces any remaining graphics instructions out of the pipeline and to the display

gluPerspective(fovy, aspect, near, far)

fovy - field of view (angle of view in degrees 0.0 - 180.0 aspect - aspect ratio (width/height) near, far - front and rear clipping planes

viewing volume

has boundaries at the top, bottom, left side, right side, front and back, front and back boundaries are called front clipping plane and back clipping plane

textures

images (supplied or generated) that can be applied to objects, faces, lines, vertices

Subdividing objects

increase the number of vertices, edges and faces in an object.

defining a material as a specular materials does what?

indicates that light reflected from the material will be reflected in a concentrated or focused way.

glBegin(GL_POLYGON)

instructs OpenGL to create a polygon using the contained vertices

depth buffer

keeps track of the depth of an object in a view, also called the z-buffer

ambient light

light that just fills the space or scene

Perspective viewing volume

lines are not parallel, the volume grows as it recedes from the viewer

Orthographic viewing volume

lines are parallel, if you measured edges (in your display window) of the same orientation, they would measure the same length

Projection (in 3D graphics)

mapping viewable fragments of the 3D model to pixels in a 2D display window

directional light (OpenGL)

modeled as if light is infinitely far away - rays are parallel like sunlight w = 0

positional light (OpenGL)

modeled as if the source has a specific location in the scene and light radiate in all directions (mostly) w = 1

Pixels

most atomistic elements of a graphic display

glTranslatef(x,y,z)

move the object x units on the x axis and y units on the y axis and z units on the z axis

Minification

multiple texels need to be mapped to a single pixel in the frame buffer

Rasterize

must determine which pixels will be inside a primitive (polygon) rasterizer organizes vertex and primitive information in terms the frame buffer

vertex processor

perform transformations and compute/assign color to vertex

Rotating Objects in blender

press R (for rotate) R x to constrain rotation to x axis R y to constrain to y axis R z to constrain to z axis

Scaling Objects in Blender

press S (for scale) S x to constrain change to x axis S y to constrain to y axis S z to constrain to z axis

Projection

process of mapping elements of a model in a 3D space to 2D space such as a computer screen or viewport is known as

Specular light

reflected off of an object in a specific direction, the intensity of the reflection is concentrated in the direction of the reflection, think of this as "shiny"

By convention, the coordinates for points on a 2D texture are referred to as

s & t

glScalef(x, y, z)

scales (enlarges/shrinks) the defined object or objects in the x dimension, y dimension, or z dimension

Shaders

small programs, reside in the GPU carry out pipeline function in each stage of the pipeline limited (can't intercommunicate, except through the pipeline)

Identity Matrix

square matrix with all 1s on the diagonal, all other elements = 0

front clipping plane

the closest that objects/geometry can be positioned in world coordinate space and be rendered in the visualization of the CG model

back clipping plane

the furthest back from the viewer, in world coordinate space that objects/geometry can be rendered in the view

Texel

the most elementary part of a texture - think pixel but for a texture

texture mapping

the process of attaching/applying a texture to an object, surface, line or vertex

A method for defining the vertices of complex objects is

the use of vertex arrays

A primary reason to use textures in 3D computer graphics is

to apply images to objects to create the illusion of complex surfaces

Clipping planes - near and far

too near, too far to be in computed view

Event mode

trigger evokes the measure process collect the measure and make it available to the program. places the measure (with an event ID) in an event queue. The event handler in the program fetches the measure data and responds.

Request mode

when a program needs input it halts and waits for a trigger, when it receives the trigger it processes the input data (like scanf or cin)

Clamping

where a texture is smaller than the surface the texture is applied to, a technique to "stretch" the texture to cover that surface

glPopMatrix()

will pop the current matrix off of the stack and restore what is now in second position