Ray Tracing

1. Ray Tracing

2. Ray Tracing • Highly realistic • Considerable computation time

3. Ray Tracing prp

4. Ray Tracing ambient light: kaIa diffuse light: kd (N.L) specular light: ks (H.N)ns specular reflection direction: R = u-(2u.N)N T = [(hi/hr) cos qi - cos qr] N - (hi/hr)L cos qr = √1 - (hi/hr)2 (1-cos2qi ) reflected light R L shadow ray T qr N qi hr H hi u incoming ray (viewing direction V = -u)

5. Ray Tracing main() { Select prp for (each scan line) for (each pixel in scan line) determine ray from prp through pixel pixel = Trace (ray, 1) } Trace (ray, depth) { determine closest intersection of ray with an object if (object hit) compute normal at intersection return Shade( closest object hit, ray, intersection, normal, depth) else return background_value } Shade ( object, ray, point, normal, depth) { color = ambient term for (each light) Sray = ray to light from point if (N.L>0) compute how much light is blocked by opaque and transparent surfaces, and use to scale diffuse and specular terms before adding term to color if (depth < maxdepth) if (object is reflective) Rray = ray in reflection direction from point Rcolor = Trace (Rray, depth+1) scale Rcolor by specular coeff. and add to color if (object is transparent) Tray = ray in refraction direction from point if (total internal reflection does not occur) Tcolor = Trace (Tray, depth+1) scale Tcolor by transmission coeff. and add to color return color }

6. Ray Tracing Ray equation P = P0 + s.u P: any point along the ray P0: initial position vector s: distance of P to P0 u: unit direction vector Ppix – Pprp u = ------------------ | Ppix – Pprp | Initially P0 is Ppix or prp. Update P0 and u at each intersection point on the ray with a surface. y ray path u P0 Ppix x prp z

7. Ray Tracing

8. Ray Tracing

9. Ray Tracing

10. Ray Tracing