1. Illumination and Shading Prof. Lizhuang Ma Shanghai Jiao Tong University

2. Contents Illumination Models Shading Models for Polygons Surface Detail Shadows Transparency Global Illumination Recursive Ray Tracing Radiosity The Rendering Pipeline

3. Ambient Light: :intensity of the ambient light :ambient-reflection coefficient: 0~1 Diffuse reflection: :point light source’s intensity :diffuse-reflection coefficient: 0~1 :angle: Illumination Models

4. Diffuse Reflection

5. Examples

6. – :light-source attenuation factor –If the light is a point source –Diffuse reflection: where is the distance the light travels from the point source to the surface Illumination Models

7. Examples

8. If an object’s diffuse color is where for the red component however, it should be where is the wavelength Colored Lights and Surfaces then

9. Specular Reflection

10. – :specular-reflection coefficient: 0~1 So, the Eq. can be rewritten as: Consider the object’s specular color: – : specular color The Phong Illumination Model

12. Examples

13. Calculating the Reflection Vector

14. The Halfway Vector

15. Multiple Light Sources If there are light sources, then

16. Shading Models for Polygons Constant Shading –Faceted Shading –Flat Shading Gouraud Shading –Intensity Interpolation Shading –Color Interpolation Shading Phong Shading –Normal-Vector Interpolation Shading

17. Constant Shading Assumptions –The light source is at infinity –The viewer is at infinity –The polygon represents the actual surface being modeled and is not an approximation to a curved surface

18. Gouraud Shading

19. Gouraud v.s. Phong Shading

20. Phong Shading

21. Texture Mapping = Pattern Mapping

22. Bump Mapping & Displacement Mapping

23. Shadows If light I is blocked at this point If light I is not blocked at this point

24. Scan-Line Generation of Shadows

25. Shadow Volumes

27. Transparency Interpolated transparency : transparency: 0~1 Filtered transparency :transparency color

28. Global Illumination

29. The Rendering Equation – : intensity passing from to – : emitted light intensity from to – : intensity of light reflected from to from the surface at – : the distance between and – : all surfaces if is invisible from if is visible from

30. Recursive Ray Tracing surface normal reflected ray shadow ray transmitted ray

31. The Ray Tree Intensity of reflected ray Transmission coefficient :0~1 Intensity of transmitted ray

32. – : radiosity of patch i – : rate at which light is emitted form patch i – : reflectivity of patch i – : from factor (configuration factor) – : area of patch i Since Thus The Radiosity Equation

33. Rearranging terms Therefore Progressive refinement The Radiosity Equation

34. Computing Form Factors

35. Hemisphere

36. Hemicube

37. The Rendering Pipeline Local Illumination Pipelines –z-buffer and Gouraudshading –z-buffer and Phongshading –List-priority algorithm and Phongshading Global Illumination Pipelines –Radiosity –Ray tracing

38. Rendering Pipeline for z-buffer & Gouraud Shading

39. Rendering Pipeline for z-buffer & Phone shading

40. Rendering Pipeline for List-priority Algorithm & Gouraud Shading

41. Rendering Pipeline for List-priority Algorithm & Phong Shading

42. Rendering Pipeline for Ray Tracing