1. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics CIS 736 Computer Graphics William H. Hsu Department of Computing and Information Sciences, KSU KSOL course pages: http://snipurl.com/1y5gchttp://snipurl.com/1y5gc Course web site: http://www.kddresearch.org/Courses/CIS736http://www.kddresearch.org/Courses/CIS736 Instructor home page: http://www.cis.ksu.edu/~bhsuhttp://www.cis.ksu.edu/~bhsu Readings: Sections 20.5 – 20.9, Eberly 2 e – see http://snurl.com/1ye72http://snurl.com/1ye72 NeHe tutorials: 22 (bump), 23 (sphere environment) – http://nehe.gamedev.nethttp://nehe.gamedev.net NVidia tutorial (cube environment): http://snurl.com/2214yhttp://snurl.com/2214y OpenGL documentation (transparency and blending): http://snurl.com/2216vhttp://snurl.com/2216v Advanced CG Topics 2 of 8: Mappings

2. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Online Recorded Lectures for CIS 736 Computer Graphics Project Topics for CIS 736 Advanced Topics in Computer Graphics (8)  1. Filters for Texturing – first month  2. More Mappings – second month  3. Advanced Lighting Models – second month  4. Advanced Ray-Tracing – first month  5. Advanced Ray-Tracing, concluded – second month  6. Global Illumination: Photon Maps (Radiosity) – third month  7. More on Scientific, Data, Info Visualization – third month  8. Terrain – first month Recommended Background Reading for CIS 736 Shared Lectures with CIS 636 (Computer Graphics)  Regular in-class lectures (35) and labs (7)  Guidelines for paper reviews – second month  Preparing project presentations, demos for graphics – third month

3. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Lecture Outline References: Wohn (2002) Mappings Explained Intermediate Surface Method Revisited (Cylinder, Sphere, Plane, Box)  Reflected ray  Object normal  Object centroid  Intermediate normal Cuboid vs. Sphere Mappings: Tradeoffs Bump Mapping: Perturbing Surface Normals Displacement Mapping: Perturbing Geometry Reflection Mapping aka Environment Mapping: Object-Centered Imaging Transparency Mapping: Viewer-Centered Imaging with Refraction Using Single-Pass and Multi-Pass Rendering Noise Models (especially 2-D) Read: Handout 1 (Texturing and Mapping)

4. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Source Material CS492A Computer Game Development Fall 2002 Course: http://vr.kaist.ac.kr/courses/cs492/http://vr.kaist.ac.kr/courses/cs492/ Instructor: http://vr.kaist.ac.krhttp://vr.kaist.ac.kr Kwangyun Wohn Korea Advanced Institute of Science and Technology (KAIST) Virtual Reality Lab

5. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Review: Texturing Adapted from slides © 2002 Gröller, E. & Jeschke, S. Vienna Institute of Technology

6. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2005 Isenberg, T., University of Calgary (now at U. Groningen) Review: Properties and their Mappings

7. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2005 Isenberg, T., University of Calgary (now at U. Groningen) Some Mappings Texture, Transparency, Reflection, Shadow

8. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Contents Introduction Two-dimensional texture maps to polygon mesh object Two-dimensional texture domain to bi-cubic parametric patch objects Bump mapping Environment or reflection mapping Three-dimensional texture domain techniques Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

9. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Introduction [1] Texture mapping  Migrate into hardware.  Developed in parallel with research into global illumination algorithms – ray tracing and radiosity. Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

10. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Introduction [2] Texture  Color  Specular color  Normal vector perturbation  Displacement mapping  Transparency Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

11. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Color Texture Map Texture  Very complex geometry without texture  Simple geometry with texture Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

12. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Specular Color Specular light term can be calculated by texture mapping.  Gourad / Phong [Intensity / Normal]  Reflected Ray Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

13. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Normal Vector Perturbation Normal vector perturbation for express natural appearance. Bump mapping [J.Blinn] Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

14. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Displacement Mapping Perturb the geometry. Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

15. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Transparency Control the opacity of a transparent object. Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

16. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Two-Dimensional Texture Maps onto Polygon Mesh Objects During the modeling phase, he/she associate texture coordinates with polygon vertices. Two main mapping algorithm  Inverse mapping [screen order]  Forward mapping [texture order] Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

17. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Inverse Mapping By bi-linear interpolation  Screen coordinate (x,y)  bi-linear interpolation -> (u,v) Two linear projective transform equation  X = f1(u,v)  Y = f2(u,v) Inverse Matrix (homogeneous coordinate)  (u,v,q) = M(x,y,w) T Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

18. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Inverse Mapping using Intermediate Surface Using an ‘ easy ’ Intermediate surface onto which the texture is initially projected. [Bier and Sloan 1986] Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

19. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Intermediate Surface [1] (a)PlaneCylinderSphere Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

20. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Intermediate Surface [2] Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

21. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Four Possible Mappings Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

22. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Cylindrical Mapping: Centroid Method

23. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Cylindrical Mapping

24. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Technique developed by J. Blinn in 1978. Surface normals are perturbed for producing local geometric variations on a smooth surface. Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bump Mapping [1]

25. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bump Mapping [2]

26. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bump Mapping [3]

27. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Perturbation of surface normals only No geometry perturbation Same silhouette edges Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bump Mapping [4]: Summary and Example

28. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Bump Mapping Internals [1] Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

29. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics New Imaginary Surface P ’ Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bump Mapping Internals [2]

30. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bump Mapping Internals [3]

31. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bump Mapping Internals [4]

32. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Intensity Calculation = Gouraud component + Normal Map component Key Idea = D Computation  Image subtraction Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bump Mapping: Multi-Pass Technique [1]

33. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Render with bump map (1) Render with bump map which are shifted by tangent space (2) Subtract Two Projected Image (1) – (2) Finally Render Object without texture map  Step (1) and (2) compute D.L  All Done in the frame buffer, Conventional Texture Mapping Unit can be used. Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bump Mapping: Multi-Pass Technique [2]

34. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Frame Buffer Multi-Pass Case Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Multi-Pass Texturing

35. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Single-Pass Case Frame Buffer Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Single-pass Texturing

36. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Environment Mapping aka reflection mapping [1] Reflection Mapping: Blinn [1977] Purpose  Rendering shiny objects (silvered, mirrored, etc.)  Reflect the environment in which objects are placed Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

37. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Environment Mapping aka reflection mapping [2]

38. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Relative size of Object and Environment important  Object must be smaller than environment  Otherwise: image reversal (“outside”) Object can only reflect environment, not itself Separate map required for each object Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Environment Mapping aka reflection mapping [3]

39. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Reflected Ray R v = 2(N  V) N – V Same as ray tracing! Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

40. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Bounding Volume Method  Cube  Sphere Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bounding Box / Cuboid Mapping [1]

41. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Environment map captured at teapot position Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bounding Box / Cuboid Mapping [2]

42. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Bounding Sphere mapping [1]: Tradeoffs with Bounding Box Cubic Mapping  Consists of six planes  Accesses six planes for each object Tradeoffs  Lots of culling  Distortion (see slides 19 & 41) Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

43. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Advantage: Speed Tradeoff: Non-Uniform Sampling Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bounding Sphere mapping [2]: Pro and Con

44. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics a)Cubic perspective b)Mercator c)Orthographic Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Bounding Sphere mapping [3]: Projections

45. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Three-dimensional texture domain techniques To overcome surface rendering  Surface curvature restrict texture compression  Non trivial surface topology  Can ’ t be mapped by 2-D texture Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

46. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Three-dimensional noise Perlin (1985)  Define noise function  three-dimensional position as input and returns single scalar value Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

47. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics 1-D Noise Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

48. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Controlled by amplitude Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

49. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics 2-D Noise [1] Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

50. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) 2-D Noise [2]

51. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Animating Turbulence [1] RGB space Blue, green, red Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST)

52. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Turbulence function (Perlin noise) Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Animating Turbulence [2]

53. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Series of turbulence functions Used to simulate keyframe animation Adapted from slides © 2002 Wohn, K., Korea Advanced Institute of Science and Technology (KAIST) Animating Turbulence [3]

54. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Advanced CG 1 of 8: TexturingCIS 636/736: (Introduction to) Computer Graphics Summary Mappings Explained  Definitions  Design principles Intermediate Surface Method Revisited Methods: Reflected Ray, Normal, Centroid, Intermediate Normal Cuboid vs. Sphere Mappings  Tradeoffs: different distortions  Projections Bump Mapping (Normals) vs. Displacement Mapping (Geometry) Reflection Mapping aka Environment Mapping Transparency Mapping Using Single-Pass and Multi-Pass Rendering Noise Models (especially 2-D)  Interpolation  Turbulence

55. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Advanced CG 1 of 8: TexturingCIS 636/736: (Introduction to) Computer Graphics Terminology Mapping: projecting or generating image on object Intermediate Surface Method Revisited (Cylinder, Sphere, Plane, Box) Four Mapping Methods  Reflected ray  Object normal  Object centroid  Intermediate normal Bounding Box vs. Bounding Sphere Bump Mapping: Perturbing Surface Normals Displacement Mapping: Perturbing Geometry Reflection Mapping aka Environment Mapping: Object-Centered Imaging Transparency Mapping: Viewer-Centered Imaging with Refraction Using Single-Pass and Multi-Pass Rendering Noise Models (especially 2-D)

56. Computing & Information Sciences Kansas State University Advanced CG 2 of 8: MappingsCIS 636/736: (Introduction to) Computer Graphics Next: Advanced CG 3 of 8 Lighting (Blinn-Phong, Torrance- Sparrow) More on Filters for Texturing Mappings  Bump vs. Displacement  Environment / Reflection  Transparency  Decaling / Shadow Maps Shadow Stencil Buffer in OpenGL Texturing and Shading Advanced 3 & 6 of 8: Lighting Models, Radiosity Advanced 4-5 of 8: Ray Tracing  4. Advanced, Part 1 of 2: Basics and Distributed Ray Tracing  5. Advanced, Part 2 of 2: Improving Ray Tracers Advanced 7 of 8: Visualization Advanced 8 of 8: Terrain