CSC 418 2504 Winter 2003 Tutorial Notes - Mar 14

CSC 418/2504 Winter 2003 Tutorial Notes - Mar 14 file:///C:/patrick/www/dgp/csc418/notes/ray_tracing_tutorial/raytracing_...Ray TracingIdeaDirect approach: Trace rays from the light source to the eye. Lots of rays are wasted because they never reach the eye.The Ray Tracing approach: Trace rays starting from the eye, through the image plane and into the scene.Primary rays are those which directly intersect an object (the part closest to the eye) from the eye point.Secondary rays are shot from this intersection point. There are three types: Shadow raysReflected raysRefracted rays. Shadow rays are directed at the light sources and determine if the region is in shadow. Reflected andrefracted rays model the mirror-like and transparency characteristics of the object. A local lighting model isapplied at the intersection point (with an ambient term) and combined with the reflected ray and refracted raycontributions. Ray Tracing models specular reflection and refractive transparency well, but models globallighting contributions poorly. This is because it uses a directionless ambient light term for approximatingdiffuse scattering. Radiosity methods are used to overcome this deficiency.basic algorithmraytrace(ray){ find closest intersection cast shadow ray, calculate colour_local if (object is shiny) colour_reflect = raytrace(reflected_ray) if (object is transparent) colour_refract = raytrace(refracted_ray) colour = k1*colour_local + ...