Medical Visualization - Illustrative Visualization 2 (Summary) J.-Prof. Dr. Kai Lawonn

Transcription

1 Medical Visualization - Illustrative Visualization 2 (Summary) J.-Prof. Dr. Kai Lawonn

2 Hatching 2

3 Hatching Motivation: Hatching in principle curvature direction Interrante et al

4 Hatching Hatching approaches: Image-based: Real time but no frame coherence (Rössl et al. 2000, Ritter et al. 2006) Object-based: Frame coherence, but often no real-time capability (Dong et al. 2003, Zorin et al. 2004) Texture-based: Frame coherence, real-time capable, but requires surface parametrization -> creation of texture coordinates (Praun et al. 2000) Rössl, et al Dong et al Praun, et al

5 Hatching Texture-based: Use of Tonal Art Maps as texture patches (Praun et al. 2001) Each line (stroke) is contained in different scales and tones Enables frame coherence, shaded illustrations and mip-mapping [Praun et al. 2001] 6

6 Hatching Texture-based (results): Problem: Texture distortions at discontinuities in the vector field Praun et al

7 Hatching Principle curvature direction Optimize vector field Cylinder for ensuring distances Zander et al

8 Hatching Curvature calculation on GPU Projection of the hatching texture in image-space Kim et al

9 ConFIS Spatial impression Salient regions [Lawonn et al.; Streamlines for Illustrative Realtime Rendering, CGF] 10

10 ConFIS Stands for? ConFIS Contour: Contour Margin Feature: Feature Regions Illustrative Streamlines Streamlines for Illustrations 11

11 Limitations 12

12 Limitations 13

13 Limitations 14

14 ConFIS+ 15

15 LIC based Approach 16

16 Method 1. Feature Vectorfield 2. Feature Region 3. Line Integral Convolution 17

17 Method - Feature Vectorfield 18

18 Method - Feature Region 19

19 Method - Feature Region Ambient Occlusion (SSAO) 20

20 Method - Feature Region 21

21 Method - Final 22

22 Method - Final 23

23 Hatching Light gradient Look-up table Lawonn et al

24 Stippling 25

25 Stippling Definition: Technique where objects are illustrated with points Density of the points determine the color of the object (form, texture, shading) Usually black points on white background [Guthrie 2004] [Strothotte und Schlechtweg 2002] 26

26 Stippling Object-based: Starting point: surface (Pastor et al. 2003) or volume dataset (Lu et al. 2002, Busking et al. 2008) Points on vertices or voxel positions Pastor et al.: Builds point hierarchyies through simplification of the triangular meshes Selection of the hierarchy plane according to the shading [Pastor et al. 2003] 27

27 Stippling Texture-based: Problems: surface parametrization, selection of surface texture simple cube mapping of a stippling texture on teapot model Generates distortions, [Baer 2005] 28

28 Stippling Texture-based: Solution: Polycube approach according to Tarini et al Distribution of the object room into cubes Application of a modified cube mapping for each cube Advantage: minimizes distortions, low preprocessing 29

29 Advanced Texture Mapping 30

30 Advanced Texture Mapping Preprocessing: Generation of a vector field (curvature or model-based) Local parametrization through lapped textures Surface Vector field Local texture patch Texture blending at overlapping texture patches Lapped Textures [Praun et al., 2000] 31

31 Advanced Texture Mapping Generate polycubes for surfaces Simplified texturing PolyCube-Maps [Tarini et al. 2004] 32

32 Illustrative Shading 33

33 Illustrative Shading Shading Maps: Creation of shading maps that serve as lookup table for the placement of illustrative techniques, e.g. stippling, hatching, color saturation Calculation of local features per vertex, e.g. normal, curvature, weighting, distances to the viewer/between objects, + illumination per pixel Coding in single shading maps and weighted combination of all maps Brightness of each pixel determines the weigth of the corresponding method 34

34 Illustrative Shading Shading Maps: Examples of different shading maps [Tietjen et al. 2008] 35

35 Illustrative Shading Shading Maps (Result): Left diffuse illumination, right locally adapted shading, [Tietjen et al. 2008] 36

36 Illustrative Shading Scalar field generation on surface Assignment in look-up table 3D model feature line stylization [Hao et al. 2010] 37

37 Smart Visibility 38

38 Smart Visibility [Viola et al. 2004] 39

39 Illustrative Volume Rendering 40

40 Illustrative Volume Rendering Different style transfer functions for volume rendering Style transfer functions [Bruckner et al. 2007] 41

41 Illustrative Volume Rendering (From: Kindlmann et al. 2003) 42

42 Illustrative Volume Rendering Particle system [Van Pelt et al. 2010] 43

43 Medical Illustration and Surgical Planning 44

44 Medical Illustration and Surgical Planning Combination of different rendering styles Combination of techniques for surgery education and planning [Tietjen et al. 2005] 45

45 Vessel and Blood Flow Visualization 46

46 Vessel and Blood Flow Visualization Lecture 11 47

47 Perception-based Evaluation 48

48 Perception-based Evaluation Studies: Comparison of shaded illustrations with hand-drawn and computer-generated contour lines Task: Estimation of the surface normal via Gauge primitives Result: Line graphics describe the surface form similar good as shadings Computer-generated illustrations very similar to hand drawings Cole et al. 2008/

49 Perception-based Evaluation Shape perception of with texture [Interrante et al. 1997] Where people draw lines [Cole et al. 2008] NPR in context [Isenberg et al. 2006] Perceptual evaluation [Baer et al., 2011] 50

50 Summary Illustrative Visualization convey information instead of realism Suitable for focus-and-context visualization Not usable for diagnostics Usability depends on application In general preprocessing is necessary Good approximation of computer-generated illustrations 51

51 Questions??? 52

52 Possible Questions 53

53 Possible Questions Explain the idea of hatching. 54

54 Possible Questions Explain the idea of hatching. Definition: Selective line placement (strokes) Variation of line distance, length, style, direction Motivation: Description of surface characteristics and shadings Highlighting of spatial correlations and structure differentiation Use for context visualizations in therapy planning 55

55 Possible Questions Mention and explain three different hatching approaches. 56

56 Possible Questions Mention and explain three different hatching approaches. Image-based: Real time but no frame coherence Object-based: Frame coherence, but often no real-time capability Texture-based: Frame coherence, real-time capable, but requires surface parametrization -> creation of texture coordinates 57

57 Possible Questions What vector field is usually used for the hatching directions? 58

58 Possible Questions What vector field is usually used for the hatching directions? Principle curvature direction 59

59 Possible Questions In the following you see three texture maps with constant scale (the method by Praun et al. is used). Are this proper Tonal Art Maps? 60

60 Possible Questions In the following you see three texture maps with constant scale (the method by Praun et al. is used). Are this proper Tonal Art Maps? NO 61

61 Possible Questions In the following you see three texture maps with constant scale (the method by Praun et al. is used). Are this proper Tonal Art Maps? NO 62

62 Possible Questions In the following you see three texture maps with constant scale (the method by Praun et al. is used). Are this proper Tonal Art Maps? 63

63 Possible Questions In the following you see three texture maps with constant scale (the method by Praun et al. is used). Are this proper Tonal Art Maps? NO 64

64 Possible Questions In the following you see three texture maps with constant scale (the method by Praun et al. is used). Are this proper Tonal Art Maps? 65

65 Possible Questions In the following you see three texture maps with constant scale (the method by Praun et al. is used). Are this proper Tonal Art Maps? YES 66

66 Possible Questions Is ConFIS an object-based, texture-based or image-based hatching method? 67

67 Possible Questions Is ConFIS an object-based, texture-based or image-based hatching method! 68

68 Possible Questions Explain shortly the idea of ConFIS. 69

69 Possible Questions ConFIS Contour: Contour Margin Feature: Feature Regions Illustrative Streamlines Streamlines for Illustrations 70

70 Possible Questions What vector field uses ConFIS+ to generate the hatches? 71

71 Possible Questions What vector field uses ConFIS+ to generate the hatches? Light gradient 72

72 Possible Questions What geometric primitives are used for stippling and hatching? 73

73 Possible Questions What geometric primitives are used for stippling and hatching? Stippling: points (point textures) Hatching: lines 74

74 Possible Questions Think of an advantage that hatching has over stippling. Which information can be conveyed this way? 75

75 Possible Questions Think of an advantage that hatching has over stippling. Which information can be conveyed this way? Lines are directed not only density can be conveyed Use principal curvatures as stroke directions 76

76 Possible Questions Describe one smart visibility technique including a possible application. 77

77 Possible Questions Describe one smart visibility technique including a possible application. Cut away: hide parts of the surface to make inner information/ structures visible Tumor 78

78 Possible Questions Mention a way to evaluate the spatial impression of feature line techniques. 79

79 Possible Questions Studies: Comparison of shaded illustrations with hand-drawn and computer-generated contour lines Task: Estimation of the surface normal via Gauge primitives Result: Line graphics describe the surface form similar good as shadings Computer-generated illustrations very similar to hand drawings Cole et al. 2008/