LIGHT AND MATERIALS Flashcards
perfect Reflection
If light reflects, we will see a shiny surface
Mirrored surfaces tend to be metal
along as the surface is flat
the incoming angle and outgoing angle will be equal
angle of incidence = angle of reflection
usually the colour and the shape of the image is preserved
Diffuse reflection
an incoming light scatters off in many directions
The light is penetrating the surface in a tiny amount then being reflected (bounced around) so comes out in many directions
Specular reflection
Mostly bounced off in one direction but quite scattered in that direction
gives a hard shiny effect
In the real world
Things are less tidy
usually a combination of diffuse and specular
surfaces are much more uneven
we use the BRDF to try to help model this
What is the wavelength range for S cone
400-500nm
Blue
What is the wavelength range for M cone
450-600nm
Green
What is the wavelength range for L cone
475-650nm
Red
Why can we not have monochromatic purple
Blue and red are not beside each other in the visible light spectrum
So it is always a mixture of L and S (maybe a bit of M) but not an actual monochromatic segment of the spectrum
Whereas orange can be because green and red are beside each other
what is the BRDF a ration of
the ratio between radience and irradience
It is a function applied to the according light rays
What is the radience
The radiant flux emitted, reflected, transmitted or received by a given surface
BRDF measuring in real life
Need a gonio metre
Create complicated 3d models of shape
Subsurface scattering
the light that bounces around just beneath the surface
like the red glow we see with light on our skin
BSDF
Bidirectional scattering distribution function
The combination of all bidirectional light functions
