1. 1 CSCE 641: Computer Graphics Lighting Jinxiang Chai

2. Scan conversion 3D Rendering pipeline Modeling transformation lighting Viewing transformation Project transformation Clipping Image Transform into 3D world system Illuminate according to lighting and reflectance Transform into 3D camera coordinate system Transform into 2D camera system Clip primitives outside camera’s view Draw pixels (includes texturing, hidden surface, etc.)

3. Scan conversion 3D Rendering pipeline Modeling transformation lighting Viewing transformation Project transformation Clipping Image Transform into 3D world system Illuminate according to lighting and reflectance Transform into 3D camera coordinate system Transform into 2D camera system Clip primitives outside camera’s view Draw pixels (includes texturing, hidden surface, etc.)

4. Outline Ambient, diffuse and specular light Light attenuation & spot lights

5. Lighting/Illumination Color is a function of how light reflects from surfaces to the eye Global illumination accounts for light from all sources as it is transmitted throughout the environment Local illumination only accounts for light that directly hits a surface and is transmitted to the eye

6. Direct and Indirect Light

7. Global Illumination II

9. Lighting/Illumination Color is a function of how light reflects from surfaces to the eye Global illumination accounts for light from all sources as it is transmitted throughout the environment Local illumination only accounts for light that directly hits a surface and is transmitted to the eye

10. Reflection Models Definition: Reflection is the process by which light incident on a surface interacts with the surface such that it leaves on the incident side without change in frequency.

11. Reflection Models Definition: Reflection is the process by which light incident on a surface interacts with the surface such that it leaves on the incident side without change in frequency.

12. Reflection Models Definition: Reflection is the process by which light incident on a surface interacts with the surface such that it leaves on the incident side without change in frequency.

13. Reflection Models Definition: Reflection is the process by which light incident on a surface interacts with the surface such that it leaves on the incident side without change in frequency.

14. Types of Reflection Functions Ideal Specular  Reflection Law  Mirror

15. Types of Reflection Functions Ideal Specular  Reflection Law  Mirror Ideal Diffuse  Lambert’s Law  Matte

16. Types of Reflection Functions Ideal Specular  Reflection Law  Mirror Ideal Diffuse  Lambert’s Law  Matte Specular  Glossy  Directional diffuse

17. Materials PlasticMetalMatte From Apodaca and Gritz, Advanced RenderMan

18. Illumination Model Ambient Light  Uniform light caused by secondary reflections Diffuse Light  Light scattered equally in all directions Specular Light  Highlights on shiny surfaces

19. Ambient Light A =intensity of ambient light k a =ambient reflection coefficient Really 3 equations! (Red, Green, Blue) Accounts for indirect illumination Determines color of shadows

20. Total Illumination

21. Diffuse Light Assumes that light is reflected equally in all directions Handles both local and infinite light sources  Infinite distance: L doesn’t change  Finite distance: must calculate L for each point on surface Surface

22. Diffuse Light C = intensity of point light source k d = diffuse reflection coefficient = angle between normal and direction to light Surface

23. Total Illumination

25. Materials PlasticMetalMatte From Apodaca and Gritz, Advanced RenderMan

26. Specular Light Perfect, mirror-like reflection of light from surface Forms highlights on shiny objects (metal, plastic) Surface

27. Specular Light C =intensity of point light source k s =specular reflection coefficient =angle between reflected vector (R) and eye (E) n =specular coefficient Surface

28. Finding the Reflected Vector Surface

29. Finding the Reflected Vector Surface

30. Finding the Reflected Vector Surface

31. Finding the Reflected Vector Surface

32. Finding the Reflected Vector Surface

33. Finding the Reflected Vector Surface

34. Total Illumination

38. Multiple Light Sources Only one ambient term no matter how many lights Light is additive; add contribution of multiple lights (diffuse/specular components)

39. Total Illumination

41. Other Lights Attenuation caused by fog, smoke Spot lights

42. Attenuation Decrease intensity with distance from light d = distance to light r = radius of attenuation for light

43. Attenuation

45. Spot Lights Eliminate light contribution outside of a cone Surface

46. Spot Lights Eliminate light contribution outside of a cone Surface

47. Attenuation

48. Spot Lights

50. Implementation Considerations Surface

51. Implementation Considerations Typically choose Clamp each color component to [0,1]

52. Opengl Functions how to set up light sources (light source pos - light source position and type - light source colors - radial-intensity attenuation - spotlights how to specify global lighting parameters how to specify surface properties

53. Next Lecture Shading Texture mapping & others