Lecture 6 (Illumination Models) Flashcards
What are the different surface types?
- Self-luminious
- Refractive
- Translucent
- Reflective (diffuse)
- Reflective (specular)
Give an example of a self-luminious surface type.
The sun
- Any object that emits its own light
WTF is a ‘Refractive’ surface type? And give an example
Changes direction of light as it passes through (due to change in transmission medium)
e.g. Water or glass
WTF is a ‘Translucent’ surface type?
Scatters light that passes through it
Break down Reflective surface types.
Diffuse and Specular
WTF is a ‘Reflective (Diffuse)’ surface type?
Reflects light in all directions (scattered)
e.g. Carpets, Rugged surfaces
WTF is a ‘Reflective (Specular)’ surface type?
Reflects light at the same angle as the incidident ray
e.g. Glossy surfaces, polished steel
WTF is the difference between ‘Diffuse’ and ‘Specular’ surface types?
Diffuse reflects light in all directions (scattered).
Specular reflects light in one direction.
What factors must be considered when choosing an illumination model?
Realism and computational cost.
Must balance between the two.
What are the components of light?
- Ambient
- Lambertian (diffuse)
- Specular
WTF is ‘Ambient’ component in lighting?
Light rays coming UNIFORMLY from all directions hitting the object
WTF is ‘Specular’ component in lighting?
Highlights and glossiness
WTF is ‘Phong Illumination/reflection model’?
Combines all three components of light
- Ambient Illumination
- Lambertian (diffuse) Reflection
- Specular Reflection
WTF is an ‘Isotropic Surface’?
The relationship between the incoming and outgoing direction of light is the same over the whole surface (otherwise anisotropic)
- Illumination models generally only consider isotropic sufrace
What is simple illumination models?
Do not consider shadows, reflections or photon-based effects
What is full ray tracing
Considers all rays of light -> very computationally complex
What factors affect/influence Lambertian (diffuse)?
Distance of the surface from the light source and angle of light source???
What factors affect/influence Specular?
Surface orientation & distance of both viewer and light source
In real scenes, what are the variations in shading over objects caused by?
- Surface material
- Orientation of surfaces
- Nature and direction of light sources
- View direction
- Shadows
Why do certain materials and certain rock or stone faces look different depending on the viewing angle?
This is the result of asymmetric texture
What are the illumination model umbrellas?
- Simple illumination models
- Full-ray tracing
What is the radiated light intensity formula (Ambient Component)?
Light Intensity = (intensity of the ambient light) * (percentage of the light reflected by the object)
WTF is Lambertian (Diffuse) Component?
Light is re-radiated uniformly in all directions
- This is why a projector image is the same no matter where you are viewing it from
With regards to Lambertian, what does brightness depend on?
Depends on the angle between the direction of the light source and the surface normal