CS426 Video 12 Illumination models Phong, Principled BSDF

Flashcards reviewing illumination models, Phong shading, and Principled BSDF from CS426 Video 12.

What are the three types of illumination discussed?

Ambient, Diffuse reflection, and Specular reflection

What is Lambertian reflection a special case of?

Diffuse reflection

Describe Ambient Illumination

As if the object produced the light itself or is illuminated equally from all directions.

Describe Diffuse Illumination

Light from a point source reflected from a dull or matt surface.

What defines Lambertian reflection?

Viewed intensity is constant for all viewing angles; luminance is isotropic.

When does specular reflection occur?

When light shines on polished surfaces.

What happens to the apparent surface brightness in Lambertian reflectance as the viewing angle gets shallower?

The source area increases, keeping the apparent surface brightness the same.

How is Lambertian reflectance used in graphics applications?

To model diffuse reflection.

What does the normal to the polygon surface allow you to calculate?

The cosine value (using the dot product).

What is the Phong illumination model a mixture of?

Diffuse and specular reflectors.

In the Phong model, what varies with the angle of incidence?

The relative amounts of diffuse and specular reflection.

In the Phong illumination model, what does a specular reflection exponent (n) of 0 indicate?

Diffuse only

List the parameters that Phong Shading allows you to control simultaneously.

Ambient, Diffuse, and Specular lighting

What does BSDF stand for?

Bidirectional scattering distribution function

What two functions make up the BSDF?

BRDF (bidirectional reflectance distribution function) and BTDF (bidirectional transmittance distribution function)

What does GGX stand for?

Ground Glass Unknown

What does the 'Subsurface Radius' parameter in Blender BSDF control?

Average distance that light scatters below the surface.

In Blender BSDF, what does the 'Metallic' parameter control?

Blends between a non-metallic and metallic material model.

What does the 'Anisotropic' parameter control in Blender BSDF?

Amount of anisotropy for specular reflection.

What does the 'Sheen' parameter in Blender BSDF simulate?

Amount of soft velvet like reflection near edges, cloth.

What does the 'Clearcoat' parameter control in Blender BSDF?

Extra white specular layer on top of others, car paint.

What is the function of the 'Transmission' parameter in Blender BSDF?

Mix between fully opaque surface (0) and glassy (1).

What does the 'Alpha' parameter do in Blender BSDF?

Controls the transparency of the surface, with 1.0 being fully opaque.