3D Modeling Lighting & Rendering 2

Question 1

What is subsurface scattering (SSS) and for which material type is it most commonly used?

Accepted Answer

A technique that simulates light penetrating and scattering beneath a surface; most used for skin, wax, and marble

Answer

A noise-reduction algorithm applied during rendering; most used for metallic surfaces

Answer

A method for scattering UV islands across a texture atlas; most used for hard-surface models

Answer

A particle system effect for simulating dust or fog; most used for environmental scenes

Question 2

What does 'depth of field' simulate in a 3D render?

Accepted Answer

The optical camera effect where objects outside the focal plane appear blurred

Answer

The distance at which objects begin to clip and disappear from the camera view

Answer

The range of shadow sharpness based on light source distance

Answer

The Z-depth gradient used to calculate fog density in a scene

Question 3

In PBR rendering, what distinguishes a metallic material from a non-metallic (dielectric) material in terms of reflectivity?

Accepted Answer

Metals have no diffuse component and their reflections are tinted by the albedo color; dielectrics have both diffuse and specular components with white reflections

Answer

Metals reflect only green light wavelengths while dielectrics reflect all wavelengths equally

Answer

Metals require subsurface scattering to render correctly; dielectrics do not

Answer

Metals use a roughness value of exactly 0.5; dielectrics can have any roughness value

Question 4

What is a light probe (or irradiance probe) used for in real-time 3D rendering?

Accepted Answer

A data structure that captures and stores lighting information at a point in space to simulate global illumination in real time

Answer

A diagnostic tool for measuring the luminance output of a virtual light source

Answer

A post-process filter that adjusts the color temperature of all lights in a scene

Answer

A device used on set to measure real-world lighting for visual effects matching

Question 5

What causes 'fireflies' (bright speckling noise) in path-traced renders, and what is the most common solution?

Accepted Answer

They are caused by very bright indirect light bounces with too few samples; solved by increasing sample count or using a firefly clamp/denoiser

Answer

They are caused by too many render samples; solved by reducing the sample count

Answer

They appear when specular roughness exceeds 0.9; solved by lowering roughness values

Answer

They result from overlapping UV islands; solved by re-unwrapping the mesh

Question 6

What is volumetric lighting in 3D rendering?

Accepted Answer

A rendering effect that simulates light scattering through participating media such as fog, smoke, or dust to make light beams visible

Answer

A technique that renders light as three-dimensional objects rather than infinite rays

Answer

A method that bakes lighting into a 3D texture (voxel grid) for real-time use

Answer

A compositing technique that multiplies light passes to correct exposure

Question 7

What is the difference between a hard shadow and a soft shadow in 3D rendering?

Accepted Answer

Hard shadows have a sharp, defined edge produced by a point light source; soft shadows have gradual penumbra edges produced by area or large light sources

Answer

Hard shadows are computed by ray tracing; soft shadows are computed by rasterization

Answer

Hard shadows only appear on opaque surfaces; soft shadows also appear on transparent surfaces

Answer

Hard shadows are baked into the texture; soft shadows are calculated in real time