Visible Surface Detection

Question 1

Classification of Visible Surface Detection method

Answer 1

Object Space methods

Question 2

What are the characteristics of Image Space methods?

Answer 2

Depth Buffer Method
A buffer method
Scan line Method
Area Subdivision method

Question 3

What are the characteristics Object Space Method

Answer 3

back Face Detection
BSP Tree Method
Octree Methods
Ray-Casting

Question 4

What is Depth cueing?

Answer 4

HiddenSurfaces are diaplyed with different intensity,color or shadow to give the hint for 3D object

Question 5

What is an image space method?

Answer 5

based on pixels to be drawn on 2D
Run the complexity the number of pixel times
Space complexity is two times the number of pixels
One array for the frame buffer
One array for the depth buffer
Also,coherence properties can be used

Question 6

What is Depth Buffer algorithm?

Answer 6

Also,known as Z-buffer algorithm,image space approach
Each surface is processed separately one pixel at a time
The depth values for a pixel and the closest z value determines the color displayed in the frame buffer
Applied very efficiently on polygon surfaces,surface is processed in any order

Question 7

Two buffers used in Depth buffer algorithm

Answer 7

Refresh Buffer ,depth buffer

Question 8

In what range are z coordinates normalized

Answer 8

[0,1]

Question 9

initialize the (z) depth buffer and refresh buffer so that for all buffer position, coordinates values of depth Buff and Refresh Buff

Answer 9

0

I background

Question 10

For each surface in Polygon,z

Answer 10

DepthBuff(x,y)=z

RefreshBuff(x,y)=Isurcol(x,y)

Question 11

Polygon surface equation

Answer 11

z= (-Ax-By-D)/C

Question 12

For any scan line, the horizontal x position or vertical y position differ by

Answer 12

1 unit

Question 13

The depth value for the next position in the scan line is, at x+1,y :

Answer 13

Z’= [-A(x+1)-By-D]/C

=z - A/C

Question 14

For adjacent scan lines we can compute the x value,z value

Answer 14

x’=x-1/m

z’=z+(A/m+B)/C

Question 15

A Buffer algorithm:

Answer 15

Extension of z buffer

Antiliased,area averaged and accumulation buffer s

Question 16

Who developed surface rendering methods?

Answer 16

Lucasfilm

Question 17

A drawback of the depth-buffer method

Answer 17

Deals only opaque surfaces

Can’t accumulate intensity values for more than one surface

Question 18

Each position in A buffer can be referenced what type of data structure:

Answer 18

linked list

Question 19

Each position in the A buffer has two fields, What?

Answer 19

Depth Field

Intensity field

Question 20

if the number at position is depth

the intensity field stores the RGB

Answer 20

Positive

Question 21

if there are multiple surfaces contributions to a pixel

the intensity field stores a pointer to a linked list of surfaces

Answer 21

Negative

Question 22

What are the contents of a linked list in A buffer?

Answer 22

RGB intensity components
Opacity Parameters
Depth
Percent of area coverage
Surface identifier
Pointers to the next surface