CS 450 Midterm

The Texture Map parameter value GL_NEAREST tells OpenGL to:

If a pixel doesn't fall on an exact texel, grab the nearest texel

The topology to use when drawing a list of vertices in OpenGL is specified:

In the glBegin call

The purpose of a Z-buffer (or Depth-buffer, or Zed-buffer) is to:

Make 3D objects in front hide 3D objects in back

An OpenGL spot light

Only shines in a specific direction

What order do these appear in the shader-enabled graphics pipeline? * Fragment shader * Rasterizer * Vertex shader

Vertex, Rasterizer, Fragment

When OpenGL lighting computations are performed, the actual position of the light that is used is

Whatever was given in the "glLightfv( GL_LIGHT0, GL_POSITION,..." call times the ModelView matrix

The double buffers' roles are switched by calling

glutSwapBuffers

The GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T texture parameters tell OpenGL what to do when:

s or t is < 0. or > 1.

The output from the Fragment shader is of type:

vec4

A texture image has MxN pixels (texels). OpenGL treats its dimensions in s and t as:

1. x 1.

A "callback" function, used in the graphics programming sense, is:

A function that gets called when a particular event or situation occurs

An OpenGL object's vertices cannot be defined in

A string

A "viewport" is:

A sub-region of the overall graphics window

The reason triangle strips are very efficient is:

After the first triangle, each subsequent triangle only needs a single vertex to define it

Transformations are:

Associative

The default way that OpenGL views a 3D scene is by placing the eye:

At the origin, looking in -Z

If you setup the Texture Transformation to scale by 2.0, the appearance of the texture image on the object will differ by:

Being scaled by 0.5

A pure red light shines on a pure green object. The resulting object coloring is:

Black

In the Subtractive color scale

C+M = B

The purpose of a {Depth,Z,Zed}-Buffer is to

Correctly display near objects so they appear to be in front of far objects

The framebuffer's Z-buffer is used to hold:

Depth

Joe Graphics wrote the following code: glBegin( GL_LINE_STRIP ); for( float angle = 0.; angle <= 360.; angle += 10. ) { float x = Radius * cos( TO_RADIANS( angle ) ); float y = Radius * sin( TO_RADIANS( angle ) ); glVertex2f( x, y ); } glEnd( ); What is he trying to do?

Drawing a 2D circle outline

In Texture Mapping, the OpenGL program specifies s and t coordinate values at:

Each vertex

OpenGL shading can be specified as:

Flat or smooth

The texture environment setting of GL_MODULATE differs from GL_REPLACE by:

GL_MODULATE allows the underlying color of the surface to shine up through the texture

What is it called when we specify an XYZ position with 4 elements?

Homogeneous coordinates

In HSV color, the letters H-S-V stand for:

Hue-Saturation-Value

The Texture Map parameter value GL_LINEAR tells OpenGL to:

If a pixel doesn't fall on an exact texel, interpolate from the 4 surrounding texels

An advantage of using perspective projection instead of orthographic is:

It gives a more realistic view

An advantage of using orthographic projection instead of perspective is:

It helps in lining things up

The difference between Model Coordinates and World Coordinates is:

MC are the original object coordinates, WC have been transformed into the scene

An OpenGL surface normal can be given:

Per-face or per-vertex

In the Additive color scale:

R+G = Y

In OpenGL color, which of these is true?

Red + Green = Yellow

The argument to glBegin( ) specifies:

The topology

The purpose of texture objects and texture binding is:

To allow textures to stay resident in GPU memory and not need to be downloaded from CPU memory each time they are used

The purpose of double-buffering is

To be sure the viewer doesn't see an incomplete scene

A use for specifying an XYZ using 4 elements is

To specify a point at infinity

What is the general idea behind Texture Mapping?

To stretch an image over a piece of geometry

If Joe Graphics programs these lines of code: glRotatef( 45., 1., 0., 0. ); glTranslatef( 1., 2., 3. ); followed by drawing something, he is trying to:

Translate, then rotate that object

Alpha values are used for

Transparency

The framebuffer's Alpha value is used to specify:

Transparency

A "Display List" is:

Writing display instructions into memory to be played back later

In the glRotatef( ) function call, the angle is given in units of:

degrees

The (r,g,b) output from the Fragment shader is in the variable:

gl_FragColor

The (x,y,z) output from the Vertex shader is in the variable:

gl_Position

The (x,y,z) input to the Vertex shader is in the variable:

gl_Vertex

The input and output variables in the Vertex shader are of type:

vec4