I am wondering how radiometey relates to the Phong shading model that we learned a couple weeks ago? Are we using ray casting as a technique to implement Phong shading?
Carpetfizz
@eric99ying my intuition was that Phong shading is one of the many techniques to approximate real world effects of radiometry.
StaffJakeHoles
While Phong shading is very computationally efficient and can achieve decent results, It is not physically accurate and is an approximation of how light behaves. Just to point out some difficulties with making this making this model realistic: 1) it has to be computed once per light 2) it looks only at the surface normal and not how the light interacts 3) it doesn't conserve energy. It is possible to use phong shading with ray casting as mentioned in lecture last week. You could cast camera rays, intersect them with the scene and then do a Phong calculation at the surface point where the intersection occurred.
Full ray tracing on the other hand is much more physically accurate because it is simulating how light would bounce in the real world. This is incredible for global illumination, complicated materials and so much more. The physical accuracy from working in radiometric units is very useful for art direction. Artists can place lights in the scene with intensity values in real life units and expect them to behave as the real life equivalent would.
As to how things like diffuse light and the speculator highlight could appear with ray tracing, these would be defined in the BRDF. We will go into this in project 3-2, but tldr it tells the incoming rays how to sample the recursive ray casts and shadow rays. For example, a very shiny material would be simulated by a BRDF that directs rays all in a very similar tight direction while a diffuse BRDF might sample them spread through a wider hemisphere.
kavimehta
Are there issues in assuming that photons travel in lines (rather than waves) and in assuming that rays of light do not interfere with each other? I imagine that the effects of these properties would be fairly small but maybe with very high resolution it makes a difference
Jordanwyli
@kavimehta, you can read more about wave theory and how light is an electromagnetic wave. I recall the double-slit experiment, which you might've done in high school, showed us that light exhibits both wave and particle like properties.
https://en.wikipedia.org/wiki/Light#Wave_theory
I am wondering how radiometey relates to the Phong shading model that we learned a couple weeks ago? Are we using ray casting as a technique to implement Phong shading?
@eric99ying my intuition was that Phong shading is one of the many techniques to approximate real world effects of radiometry.
While Phong shading is very computationally efficient and can achieve decent results, It is not physically accurate and is an approximation of how light behaves. Just to point out some difficulties with making this making this model realistic: 1) it has to be computed once per light 2) it looks only at the surface normal and not how the light interacts 3) it doesn't conserve energy. It is possible to use phong shading with ray casting as mentioned in lecture last week. You could cast camera rays, intersect them with the scene and then do a Phong calculation at the surface point where the intersection occurred.
Full ray tracing on the other hand is much more physically accurate because it is simulating how light would bounce in the real world. This is incredible for global illumination, complicated materials and so much more. The physical accuracy from working in radiometric units is very useful for art direction. Artists can place lights in the scene with intensity values in real life units and expect them to behave as the real life equivalent would.
As to how things like diffuse light and the speculator highlight could appear with ray tracing, these would be defined in the BRDF. We will go into this in project 3-2, but tldr it tells the incoming rays how to sample the recursive ray casts and shadow rays. For example, a very shiny material would be simulated by a BRDF that directs rays all in a very similar tight direction while a diffuse BRDF might sample them spread through a wider hemisphere.
Are there issues in assuming that photons travel in lines (rather than waves) and in assuming that rays of light do not interfere with each other? I imagine that the effects of these properties would be fairly small but maybe with very high resolution it makes a difference
@kavimehta, you can read more about wave theory and how light is an electromagnetic wave. I recall the double-slit experiment, which you might've done in high school, showed us that light exhibits both wave and particle like properties. https://en.wikipedia.org/wiki/Light#Wave_theory