IMAGE SYNTHESIS
1
Image Synthesis• Image synthesis operations create images from other
images or non-image data• Used when a desired image is either physically impossible
or impractical to acquire• CT-image, CAD, abstract data, image composition, 3D
graphics
2
Tomography
• Creates cross-sectional images of solid 3D objects
• Based on X-ray imaging• The technique is implemented by moving an X-radiation source and an x-ray detector in parallel and opposing directions, pivoting about the plane of interest
3
Computed Tomography• Uses digital computation techniques• 2D synthetic cross-sectional image is made of 1D
projections • CT is vital for medicine
4
Computed Tomography
• Transmissive mode• Computed Tomography• Based on X-radiation
• Emissive mode• MRI (Magnetic Resonance Imaging)• PET( Positron Emission Tomography)
• Reflective mode• radar imaging, ultrasonic
5
Projections
8
2D Images From Projections (object: a ball)
9
Details of CT scanning• http://www.impactscan.org/slides/impactcourse/basic_prin
ciples_of_ct/img0.html
10
MRI = Magnetic Resonance Imaging
11
3D image from 2D´s
Videos on MRI
Physics of MRI • Patient training for MRI-imaging
12
3D Scene Construction From Images• Stereo image pairing
13
Depth Perception
• Based on:• two eyes, stereo vision (or stereoscopy)• relative object sizes• object shading and shadowing• object obscuring• atmospheric haze
14
Stereoscopy15
Stereo Image Pair• Two images of the same scene with different view angles
16
Volume Rendering Slice-Image• Slice-image is two-dimensional and has no depth• Convert 2Ds (x,y) into 3D (x,y,z)
• z is a cross-sectional surface index • z is usually coarser than x,y. Intermediate slices are
created by interpolation methods
• Voxel can represent multiple features such as brightness, color and transparency
• See: http://en.wikipedia.org/wiki/Voxel
19
Example on a voxel image
20
Voxels in videos
• Brain MRI• 3D Aorta CT
• Kinect User Interface• Brain AVM 3D MRI
21
Visualization of Non-image Data• CAD rendering (computer aided design)• Elevation data rendering • 3D scanning• Visualization of abstract data
23
CAD Rendering
24
CAD Rendering Methods• Wireframe model
• Hidden-line removal
• Solid model • Tinted solid model
25
3D Rendering
In 3D rendering following methods are used:
• A model is created from sample points
• A real object is a model • A brand new object is created
26
3D Rendering
• 3D object model can be composed of surfaces, polygons or of a combination of above
• Surfaces are utilised to render simple objects (balls, sylinders)
• An arbitary plane can be rendered by using this kind of polygons
27
Methods
• In wireframe polygons can be seen as borderlines• In hidden-line removal lines behind the polygons are
not drawn
28
Methods
• Solid model rendering• Surface and color
29
Methods
• Shaded solid model • A surface can also illustrate different materials such as metal or plastic
30
Texture and lighting
• Images we create can look like real when we add different surfaces on them and illuminate them with multiple light sources
31
Photo-realistic Rendering
• Materials, light refraction and reflections
32
33
Elevation data rendering
Elevation Model -Reflection planes
34
The Calculation of A Reflectance
35
36
37
Example of Digital Terrain Model
38
39
3D-lightingModels
40
The Use of 3D Models
• In scientific research 3D models are used to render objects which are too small, large, fast or slow to be viewed by other ways
• Examples:• atoms,• molecules,• Explosions• etc
41
The Use of 3D Models
• In industry 3D rendering before building an expensive prototype
42
The Use of 3D Models
• Commercial use and entertainment industry
• Games, movies and TV-programs
43
3D Examples
• The features of the light can be rendered well, but this requires substantial computing power
44
3D Examples
• The 3D- models have almost totally replaced the plastic models in the movie industry
45
Examples of 3D animation
•Birth
•3DDentalPlanning
•Fertilization
47