OpenGL OpenGL Lighting and Materials 3

Question 1

Which OpenGL light type simulates illumination from a very distant source like the sun, with parallel rays and no positional falloff?

Accepted Answer

Directional light

Answer

Point light

Answer

Spot light

Answer

Area light

Question 2

When specifying a light position with glLightfv(), what does setting the homogeneous w component to 0.0 indicate?

Accepted Answer

The light is a directional (infinite distance) source

Answer

The light is disabled

Answer

The light has zero intensity

Answer

The light is positioned at the origin

Question 3

Which spotlight parameter in OpenGL's fixed-function lighting defines the half-angle of the light cone in degrees?

Accepted Answer

GL_SPOT_CUTOFF

Answer

GL_SPOT_DIRECTION

Answer

GL_SPOT_EXPONENT

Answer

GL_CONSTANT_ATTENUATION

Question 4

What real-world phenomenon does light attenuation model in OpenGL?

Accepted Answer

Decrease in light intensity as distance from the source increases

Answer

Color shift of light as it bounces off colored surfaces

Answer

The angle at which light refracts through a material

Answer

Shadow casting behavior of a light source

Question 5

How does the Blinn-Phong shading model differ from the classic Phong model in GLSL implementation?

Accepted Answer

Blinn-Phong uses the halfway vector instead of the reflection vector for the specular term

Answer

Blinn-Phong uses textures while Phong uses solid colors

Answer

Blinn-Phong ignores the ambient lighting component

Answer

Blinn-Phong only works with directional lights

Question 6

Which GLSL built-in function computes the scalar product of two vectors, central to Lambert's diffuse lighting law (N·L)?

Accepted Answer

dot()

Answer

reflect()

Answer

cross()

Answer

mix()

Question 7

What is the purpose of GL_LIGHT_MODEL_AMBIENT in OpenGL's fixed-function lighting?

Accepted Answer

Defines a global ambient light that illuminates the entire scene uniformly

Answer

Sets the position of all lights simultaneously

Answer

Controls the shininess of all materials globally

Answer

Enables or disables all defined light sources at once