Http://blog.selfshadow.com/publications/s2012-shading-course/smits/s2012_pbs_pixar_model_slides_v2.pdf
Http://blog.selfshadow.com/publications/s2012-shading-course/smits/s2012_pbs_pixar_model_notebook_v2.pdf
Siggraph2012's practical physically based shading in films and game production.
Pixar.
I really like Wall-E and can finally find out what the lighting model is.
Pixar used a new illumination model in <Wall-E>. We can compare the animations before <Wall-E> and Pixar to find that the quality has been greatly improved, I used to compare the Q version. When I got to the wall-eanimation, I felt more reflected in the model style. The screen was actually the same.
Necessity
Reasons for switching to the current lighting system (which includes physical based shading and has other improvements): (I am familiar with it)
- Need a more realistic view
- More efficient rendering speed-accelerating iteration time
- Simplified Illumination Model
- Originally, the patchwork method was too complex, resulting in a long time for Shader parameter adjustment.
- Includes diffuse, specular, RIM, and other components
- In addition, it is calculated based on different types of light.
- In the past, there were a lot of Multi-Layer Materials and huge charges for rendering.
Then the requirements of the new model are simple and clear:
- Simpler parameters and easier to use
- Parameters of most materials are simplified:
- You can also perform some hack operations when necessary.
- A more realistic and stable view
- More authentic Fresnel Phenomenon
- Higher Dynamic Range
- Physical-based BRDF
- The brightness of light is higher.
- Conservation of energy
- It is important for materials to maintain a stable view in various lighting environments.
- The computing results for different materials are consistent and stable.
- In a lighting environment, it is relatively simple to call up a more real or better effect, but it is extremely difficult to use it in all environments, it can be said that it can only be achieved through correct physical-based mathematical simulation.
- You can also make some simple and clear hack adjustments.
- There are some materials and lighting
IlluminationThe behavior of light, including:
- Reflection on material surface: specular/reflection
- Diffuse Reflection and scattering
We can use two parameters:
- Roughness: In many models, roughness and specularpower can be converted to each other, and their physical meanings are also similar.
- Metallic: This is rare. It controls subsurface diffuse and mirror reflection. (This is not very clear. From the figure below, it is assumed that subsurface diffuse is controlled under the conservation of energy)
DiffuseFor non-metallic materials, there are two sources:
- Subsurface scattering, which is also the main source, is mostly affected by the Fresnel phenomenon,
- Multiple interface reflection, which increases with roughness
Metal class: only from multiple interface reflection.
Transparency)
It consists of three parts:
- Transmitted diffuse
- Transmitted specular
- Refraction
It is also related to subsurface scattering.
Layering)Tri-ACE also mentioned that it seems that this is indeed a topic for further development. That is, two layers:
Merge the following code:
The general principle is that the light goes through a transmission function and passes through to the next layer. The transmission process contains scattering. The light enters and returns through this process, which is similar to a blur filter. Remember the conservation of energy. Final result:
Final ResultBoth WALL-E and up are using this system to easily get basic material. It is also easy to create a large number of complex materials. Stable and consistent lighting. The shader does not need to be changed, so the progress will be very fast. Both simplification and flexibility are important.
