MidTerm

Question 1

What does the GLSL discard flow-control statement do?

Answer 1

discards the current fragment and ceases shader execution

Question 2

When is the discard statement available to use?

Answer 2

in fragment programs

Question 3

What line of code, used in debugging, will impose invariance on all varying variables in a shader?

Answer 3

pragma STDGL invariant (all)

Question 4

What 3 things can a precise qualifier be applied to?

Answer 4

built-in variable
user variable
function return value

Question 5

Every shader program in your application will have to follow a certain sequence of steps for each shader object. What are the 3 steps in order?

Answer 5

1. Create a shader object.
2. Compile your shader source into the object.
3. Verify that your shader compiled successfully.

Question 6

What types of variables are considered to be opaque types?

Answer 6

sampler types, image types, and atomic counter types

Question 7

What component accessors are associated with texture coordinates?

Answer 7

(s, t, p, q)

Question 8

No matter what shading stage you are programming for you will always start the structure with what line of code?

Answer 8

version

Question 9

According to the book, the recommended way to share a large buffer with the application is through use of a_________variable.

Answer 9

buffer

Question 10

What operator comes last in the GLSL order of operations?

Answer 10

comma

Question 11

___________variable types have their internal form exposed so the shader code assumes what they look like internally.

Answer 11

transparent

Question 12

Which type modifier specifies that the value is passed to the shader from the application and is constant across a given primitive?

Answer 12

uniform

Question 13

True or False

The real work in a shader is done by computing values and making decisions.

Answer 13

True

Question 14

True or False

Data is copied into shaders from OpenGL through the “in” data type variables.

Answer 14

True

Question 15

True or False

GLSL is a typed language, meaning every variable must be declared and have an associated type.

Answer 15

True

Question 16

True or False

Type conversions apply to everything, including arrays and structures.

Answer 16

False

Question 17

True or False

GLSL supports 2D and 3D vectors only.

Answer 17

False

Question 18

In OpenGL, you usually do all your drawing to the

_________buffer

Answer 18

color

Question 19

There is a set of 7 tests that a fragment has to pass prior to going into the framebuffer. List these tests in order.

Answer 19

1. Scissor test
2. Multisample fragment operations
3. Stencil test
4. Depth test
5. Blending
6. Dithering
7. Logical operations

Question 20

True or False

Multisampling and antialiasing are the same thing.

Answer 20

True

Question 21

How often should you clear out buffers in OpenGL?

Answer 21

At lease once per frame.

Question 22

True or False

The color buffer is the only buffer that holds information about a pixel.

Answer 22

False

Question 23

What 3 types of buffers are available with OpenGL?

Answer 23

color, depth and stencil

Question 24

When you make the main color buffer have a front buffer that’s displayed in your window; and a back buffer that is used to render the new image, this is referred to as what?

Answer 24

double buffering

Question 25

Data in OpenGL must be in _________ color space to be processed.

Answer 25

RGB

Question 26

Explain the term dithering.

Answer 26

It  is like half-toning in newspapers where you can show shades of gray with combinations of black and white dots.

Question 27

True or False The stencil buffer keeps track of the distance between the viewpoint and the object occupying a pixel.

Answer 27

False

Question 28

In the OpenGL pipeline, what is located between the vertex and fragment shading stages?

Answer 28

rasterization

Question 29

The __________is composed of a rectangular array of pixels that are capable of displaying a tiny square of color at that point in the image.

Answer 29

framebuffer

Question 30

_________transformations are composable.

Answer 30

Linear

Question 31

With __________projection, the viewing volume is a box

Answer 31

orthographic

Question 32

True or False Skewing is a linear transformation.

Answer 32

True

Question 33

True or False OpenGL does not have the commands to support rendering a scene through multiple viewports.

Answer 33

False

Question 34

True or False OpenGL automatically clips geometry against the near and far planes as well as the viewport.

Answer 34

True

Question 35

What is a shadow map?

Answer 35

A texture map that contains information relating to the locations of shadows within a scene.

Question 36

What is image-based lighting?

Answer 36

An illumination technique that uses an image of the light falling on an object to illuminate the object.

Question 37

The property of light that describes how a light’s intensity diminishes over distance is referred to as ___________.

Answer 37

attenuation

Question 38

__________light is light not coming from any specific direction.

Answer 38

ambient

Question 39

__________light is light scattered by the surface equally in all directions for a particular light source.

Answer 39

diffuse

Question 40

__________ highlighting is light reflected directly by the surface.

Answer 40

specular

Question 41

A ____________light is far, far away, it can be approximated as having the same direction from every point on our surface.

Answer 41

directional

Question 42

Lamps, street lights and ceiling lights that are near the scene or within the scene are________ lights.

Answer 42

point

Question 43

True or False The classic lighting model adds up a set of independently computed lighting components to get a total lighting effect for a particular spot on a material surface.

Answer 43

True

Question 44

What are 2 disadvantage of using procedural shaders over stared textures?

Answer 44

Procedural texture shaders require the algorithm to be encoded in a program. Not everyone has the technical skills needed to write such a program, whereas it is fairly straightforward to create a 2D or 3D texture with limited technical skills. * Performing the algorithm embodied by a procedural texture shader at each location on an object can take longer than accessing a stored texture. * Procedural texture shaders can have serious aliasing artifacts that can be difficult to overcome. Today’s graphics hardware has built-in capabilities for antialiasing stored textures (e.g., filtering methods and mipmaps). * Because of differences in arithmetic precision and differences in implementations of built-in functions such as noise, procedural texture shaders could produce somewhat different results on different platforms.

Question 45

What does the book say is a good reason to use stored textures over procedural textures?

Answer 45

Things that would be artwork in the real world

Question 46

What is a binormal?

Answer 46

A vector perpendicular to both a surface tangent vector and the surface normal vector.

Question 47

A sequence of pulses—usually equally spaced—used in procedural shading techniques is sometimes referred to as a(n)_______

Answer 47

pulse train

Question 48

What is the key to procedurally defining all sorts of texture patterns?

Answer 48

programmability

Question 49

A vector directed along the directional-derivative of a function is referred to as a(n) __________ Correct vector.

Answer 49

gradient

Question 50

_________mapping involves modulating the surface normal before lighting is applied.

Answer 50

Bump

Question 51

Performing full per-sample rendering for multiple samples per pixel, and then coloring the pixel based on the average of the colors found for each sample in the pixel is referred to as________

Answer 51

supersampling

Question 52

True or False Point sampling and area sampling are the same thing.

Answer 52

False

Question 53

True or False Textures generated procedurally have very high memory requirements compared with stored textures.

Answer 53

False

Question 54

True or False Textures generated by stored texture shaders have no fixed area or resolution.

Answer 54

False

Question 55

True or False A texture that contains normal perturbation values for the purpose of bump mapping is called a perturbed map.

Answer 55

False