Opengl Graphics

Front 1

bits per pixels needed for 128 gray levels?

Back 1

7 bits (2^7)

Front 2

how do you get normal vector of 3d plane represented by 3 points: a,b,c

Back 2

a = (x2-x1,y2-y1,z2-z1) b=(x3-x1,y3-y1,z3-z1)

Then cross product:

Front 3

Cross Product of axb = (a1,a2,a3)X(b1,b2,b3)

Back 3

ia2b3+ja3b1+ka1b2-ja1b3-ia3b2-ka2b1

Front 4

Benefit of motion capture system

Back 4

Realistic motion but expensive system

Front 5

difference between GL_LINE_LOOP and GL_POLYGON?

Back 5

polygon fills the shape with a solid color, line loop is an outline only

Front 6

purpose of glutInitDisplayMode(GLUT_DOUBLE)?

Back 6

double buffer system, it sets a second buffer for the display window

Front 7

A sum of a point and a vector is a point (true/false)

Back 7

TRUE. A vector is a displacement of the point to another point

Front 8

What is the dimensionality in which the vertices in OpenGL are processed?

Back 8

4D (4 dimensional)

Front 9

suppose following function:

y=sin(x), -2 <= x <= 2 (domain), -1 <= y <= 1(range)

Plot in openGL window of size 640x480 so the specified area fits the entire window. Write OpenGL code that does this.

Back 9

glMatrixMode(GL_Projection);

glLoadIdentity();

gluOrtho2D(-2,2,-1,1);

glViewPort(0,0,640,480);

Front 10

TRUE/FALSE. A translation T followed by rotation R is the same as rotation R followed by translation T

Back 10

FLASE T*R != R*T

Front 11

TRUE/FALSE The last row of a 3D affine transformation matrix is always (0 0 0 1)

Back 11

True

Front 12

What is the purpose of the OpenGL modeling transformation stack?

Back 12

Push/pop allows us to go to previous transformation states. Basically it allows for 'history'

Front 13

TRUE/FALSE A quadrilateral is always a convex polygon?

Back 13

True. Duh

Front 14

Write OpenGL statement to set the foreground color to cyan

Back 14

glColor3f(0.0,1.0,1.0)

mix of green and blue

Front 15

advantage of outline based text representation over bitmap-based?

Back 15

Outline based saves space and it's 'scale independent' ie. no loss of quality on expand/shrink

Front 16

suppose you performed a 2D rotation about the origin by the angle THETA. Write affine trans matrix that would undo this roation

Back 16

[ cosTHETA sinTHETA 0 0]

[ -sinTHETA cosTHETA 0 0]

[0 0 1 0]

[0 0 0 1]

Front 17

TRUE/FALSE a 45 degree x roll followed by 90 degree y-roll would be the same thing reversed?

Back 17

False

Front 18

describe how a cube-shaped box would be displayed on the screen under parallel projection vs. perspective projection

Back 18

On parallel each side would be truly parallel. On perspective is would change based on distance from the viewer, looks more realistic like the human eye sees. (remember skyscraper example Kang drew)

Front 19

TRUE/FALSE gluLookAt function determines the shape of the view volume

Back 19

False. gluLookAt sets viewing matrix, projection matrix sets the shape of view volume

Front 20

TRUE/FALSE In 3d graphics, the depth buffer isn't needed when rendering wireframes

Back 20

True, if you can see everything like in a wire frame, why would you need depth to determine what can and cant be seen?

Front 21

Using homogenous representation, prove that an affine combination of two points is a point.

Back 21

aA+bB

a+b=1 so a=1-b

(1-b)(x1,y1,z1,1) + b(x2,y2,z2,1) = ((1-b)x1+bx2,...etc...,1)

Front 22

How has computer graphics advanced science?

Back 22

visualization of math functions (graphs), modeling of bacteria/viruses, molecules, etc. CAD

Front 23

a smooth curve must be converted to a polyline before display. Why?

Back 23

display is a collection of discrete pixels so it can't display a truly smooth curve

Front 24

TRUE/FALSE A convex polygon is a simple polygon

Back 24

True (no intersections when convex)

Front 25

What is the color depth of True Color?

Back 25

24 (24 bits) =~ 16 million colors

Front 26

TRUE/FALSE OpenGL system has origin at the upper left

Back 26

False, it's bottom left

Front 27

What is wrong with: glColor3f(1.0, 0.3, 0.5 , 1.0);

Back 27

3f should only have 3 floating point #'s, not 4 (the alpha value)

Front 28

what does glFlush do?

Back 28

outputs current drawing in the buffer to the display. in kang's words: display everything you have specified so far

Front 29

Difference between GL_PROJECTION and GL_MODELVIEW

Back 29

GL_PROJ creates viewing volumes. MODELVIEW holds the transformations and camera view

Front 30

Aspect ratio of 1080p? (1920x1080)

Back 30

16:9 = 1920/1080

Front 31

Prove that Bezier curve always passes through first and last control points

Back 31

coeffecients determined by ((1-t)+t)^n where n is the # of control points minus one.

So if t=0, the point = 1,0,0,0,.etc.....0

if t=1, the point = 0,0,0,0.etc....,1

Front 32

Supposed their is a plane represented by triangle ABC with coordinates A(1,0,2), B(2,3,0) and C(1,2,4). Computer the normal vectore of the plane

Back 32

GET ANSWER

Front 33

Write code to generate a snowflake using the structure on left

Back 33

void drawBranch(){

drawElement();

glScaled(1,-1,1);

drawElement();

}

//In main

for (i=0,i<6,i++){

glPushMatrix();

glRotated(60*i,0,0,1); // 360degrees/6branches

drawBranch();

glPopMatrix;

}

Front 34

derive parametric form for a circle with radius r

Back 34

x = r*cos(t)

y = r*sin(t)

0 <= t <= 2PI

Front 35

Window to viewport conversion formula

Back 35

sx = Ax+B

sy = Cy+D

A=(V.r-V.l)/(W.r-W.l)

B=(V.t-V.b)/(W.t-W.b)

C=V.l-A(W.l)

D=V.b-B(W.b)

Front 36

interpolation steps

Back 36

Draw graphs.

If intermediate step = 50%, find midpoints between each given points