How can a computer draw an image that looks real?

Computer graphics is an ancient discipline with roots dating back to the 1960s. By modeling light, camera, materials and shapes, we can create virtual worlds. Rendering is interdisciplinary in nature, and combines ideas from physics, math and art.

Visible light is an electromagnetic, tranverse wave.

This means that the EM field wiggles sideways as the energy propagates forward. This wiggling in the EM field, can be seen as two fields wiggling.

But in general, you can think of light as a straight line. Light rays do not interefere with each other. light travels from source to the eye.

The simplest algorithm for modeling light is called ray tracing.

For each pixel, cast a ray from the light source, to the object underneath that pixel.

Ray tracing is an elegant technique that has its origins in lens making; Gauss traced rays through lenses by hand in the 19th century. Ray-tracing algorithms on computers follow the path of infinitesimal rays of light through the scene until they intersect a surface. This approach gives a simple method for finding the first visible object as seen from any particular position and direction and is the basis for many rendering algorithms.

In the above model, the light source is the blue concentric circle.

Reflection

Glossiness

SPD

Materials, Microgeometry, microfacets

Try changing the roughness of the cube above to affect the glossiness of the reflected light rays below.

nonmetals behave like cups of liquid the refracted light is scattered, absorbed or both.

if it’s transparent like glass, it will keep going all the way through. but usually it will be selectively be absorbed some percentage of the time. and the light that enters gets scattered at different angles if the pixel size size surface reflection term is specular refraction, absorption, scattering and more refraction, is diffuse quantify light as a number Radiance measures the intensity of light along a single ray spectral: rub bidirectional reflectance distribution function a function of l, v Lo(V) = integral of omega outgoing radiance = integral of incoming radiance TIMES times bdrf times cosine factor weighted average over incoming directions

Subsurface Scattering - TODO

Camera

The essential property of a lens is that it bends radiation, to converge upon a focus point.


  1. If every person on Earth aimed a laser pointer at the Moon at the same time, would it change color?

  • A realistic Camera model for Computer Graphics
  • See the 2007 paper Microfacet Models for Refraction through Rough Surfaces

  • See the 2001 review, A Practical Model for Subsurface Light Transport