image synthesis 1 image synthesis image synthesis operations create images from other images or...

IMAGE SYNTHESIS

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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

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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

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Computed Tomography• Uses digital computation techniques• 2D synthetic cross-sectional image is made of 1D

projections • CT is vital for medicine

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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

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Projections

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2D Images From Projections (object: a ball)

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Details of CT scanning• http://www.impactscan.org/slides/impactcourse/basic_prin

ciples_of_ct/img0.html

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MRI = Magnetic Resonance Imaging

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3D image from 2D´s

Videos on MRI

Physics of MRI • Patient training for MRI-imaging

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3D Scene Construction From Images• Stereo image pairing

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Depth Perception

• Based on:• two eyes, stereo vision (or stereoscopy)• relative object sizes• object shading and shadowing• object obscuring• atmospheric haze

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Stereoscopy15

Stereo Image Pair• Two images of the same scene with different view angles

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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

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Example on a voxel image

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Voxels in videos

• Brain MRI• 3D Aorta CT

• Kinect User Interface• Brain AVM 3D MRI

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Visualization of Non-image Data• CAD rendering (computer aided design)• Elevation data rendering • 3D scanning• Visualization of abstract data

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CAD Rendering

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CAD Rendering Methods• Wireframe model

• Hidden-line removal

• Solid model • Tinted solid model

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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

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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

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Methods

• In wireframe polygons can be seen as borderlines• In hidden-line removal lines behind the polygons are

not drawn

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Methods

• Solid model rendering• Surface and color

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Methods

• Shaded solid model • A surface can also illustrate different materials such as metal or plastic

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Texture and lighting

• Images we create can look like real when we add different surfaces on them and illuminate them with multiple light sources

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Photo-realistic Rendering

• Materials, light refraction and reflections

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Elevation data rendering

Elevation Model -Reflection planes

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The Calculation of A Reflectance

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Example of Digital Terrain Model

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3D-lightingModels

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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

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The Use of 3D Models

• In industry 3D rendering before building an expensive prototype

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The Use of 3D Models

• Commercial use and entertainment industry

• Games, movies and TV-programs

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3D Examples

• The features of the light can be rendered well, but this requires substantial computing power

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3D Examples

• The 3D- models have almost totally replaced the plastic models in the movie industry

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Examples of 3D animation

•Birth

•3DDentalPlanning

•Fertilization

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