Illumination Flashcards
(57 cards)
Illumination is the […] of light, via its […] with surfaces in a scene.
Simulation of light, via its interaction with surfaces.
There are three primary types of light source in 3D graphics…
Point light, directed light, spotlight
A spot light is located […], and emits light in a […] shape.
Located at a point in world space, and emits light in a cone shape.
A directional light is located […], and emits light in […].
Located infinitely far away, and emits light towards a direction.
A point light is located […], and emits light in […].
Located at a point in world space, and emits light in all directions equally.
A light source having attenuation means that the light…
Reduces in intensity as it travels through the world.
A […] light has no attenuation, however, a […] light does. (pick 2)
A directed light has no attenuation
A spot light/point light does.
Point lights use a form of attenuation called…
Quadratic attenuation
When a ray of light hits a surface, one of four things may happen…
Absorption, reflection, refraction or fluorescence
Global illumination considers how light interacts…
With a scene as a whole
While global illumination considers […] interactions, local illumination does not.
Object-to-object
(global reflections/refractions between objects)
One limitation of global illumination in comparison to local illumination is… (pick one)
It is computationally much more expensive, it is unsuited to real-time rendering scenarios
Local illumination considers how light interacts…
Only directly between the light source and the surface it is hitting
Diffuse reflection is the reflection of light such that…
An incident ray is reflected at many angles, rather than just one.
Diffuse reflection is considered when the surface of an object is…
Rough
Lambert’s Cosine Law describes a diffuse reflection as the product of…
The incident ray multiplied by the cosine of the angle of the surface being affected
Specular reflection is the reflection of light such that…
An incident ray is reflected at a single angle.
If perfect reflection is where the incident and reflected light make equal and opposite angles with eachother, imperfect reflection is…
Where some light is scattered away from the reflected direction
The Phong model describes a specular reflection as the product of…
The incident ray and reflection coefficient multiplied by the angle of the surface to the power of a specular reflection exponent
The Phong model is a [local/global] illumination model.
Local
If a light is a spot light with a given position and direction, then the Phong model can be simplified to the product of…
The incident ray and reflection coefficient multiplied by the product of the direction to the light and the direction of the specular reflection, to the power of a specular reflection exponent
When we add colour as an argument to the Phong model, we must treat RGB channels [separately/together].
Separately
When using Blinn-Phong, an adaptation of the Phong model, we instead calculate…
The incident ray multiplied by the product of the surface normal and the halfway vector, to the power of some specular reflection exponent
Blinn-Phong is better performant than the basic Cheap Phong method because if both the viewer and light source are far from the surface…
The halfway vector becomes constant, reducing the quantity of calculations needed
