Lecture 8

Question 1

Vizualization & common approaches

Answer 1

• Lookup tables
• Kymographs
• Renderings

Question 2

Movies

Answer 2

Movies can visualize the time dimension. Play the images fast over eachother

Question 3

Vizualizing depth dimension

Answer 3

Make them by moving depth of focus and then stacking.

Visualzing 3D gives a movie.

Question 4

Lookup tables

Answer 4

Look up tables can be used to convert the grey images to RGB image

Question 5

Kymographs

Answer 5

Kymographs can also visualize the time dimension. You can construct them along indicated lines. Kymographs are good for 1D movement. The angle of the line in a kymograph tells you about the movement speed.

Question 6

Renderings

Answer 6

Making multiple dimension images

• Volume rendering: useful in dynamics
• Surfacte rendering: Uses boundaries thus useful for static objects

Question 7

Basic principles of volume rendering

Answer 7

Volume rendering keeps density infromation, so is great for changes in rendering.

• Ray tracing
• Maximum intesnsity projection
• Alpha blending

Question 8

Ray tracing

Answer 8

Accumulation of image formation along the projection rays to make projection image.

Question 9

Maximum intensity projection

Answer 9

Way of ray tracing.

Records the intensity of a pixel as function of depth. Fast and simple but may result in distorted depth perception.

Question 10

Alpha blending

Answer 10

Way of ray tracing.

Takes the weighted sum of intensities in a ray. Oi=alphaIi+(1-alpha)Outputi+1

Question 11

Basic principles of surface rendering

Answer 11

Surface rendering focuses on giving the boundaries of objects. Requires image segmentation and mesh: image -> segmentation -> Meshing -> Rendering -> viewing

• Segmentation
• Meshing
• Marching squares
• Marching cubes
• Shading

Question 12

Marching squares

Answer 12

Make a contour model with marching squares (intensity). Set a threshold. Assign values to each cell based on binary encoding

Question 13

Marching cubes

Answer 13

Interpolate original pixel intensities to determine exact line endpoint.

Question 14

Shading

Answer 14

• Flat: Single normal vector per triangle and single color per triangle
• Gouraud: Mean vectors at the triangle vertices. Single color per triangle vertex and interpolated within triangle.

Question 15

Issues with surface rendering

Answer 15

• Smoothing and thresholding levels influence the result

- Always suse multiple visualizations and explore the complementary information

Question 16

Alternative visualization methods

Answer 16

• Orthogonal planes
• Shape primitives
• time as depth

Question 17

Shape primitives

Answer 17

Depth information -> point cloud -> mesh but also primitive detection

Question 18

time as depth