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1 IMAGE SYNTHESIS 2 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 3 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 4 Computed Tomography • Uses digital computation techniques • 2D synthetic cross-sectional image is made of 1D projections • CT is vital for medicine 5 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 8 Projections 2D Images From Projections (object: a ball) 9 10 Details of CT scanning 8b Computed_Tomography_I.ppt 11 MRI = Magnetic Resonance Imaging 3D image from 2D´s 12 Videos on MRI Physics of MRI • Patient training for MRI-imaging 13 3D Scene Construction From Images • Stereo image pairing 14 Depth Perception • Based on: • two eyes, stereo vision (or stereoscopy) • relative object sizes • object shading and shadowing • object obscuring • atmospheric haze Stereoscopy 15 Stereo Image Pair 16 • Two images of the same scene with different view angles 19 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 20 Example on a voxel image 21 Voxels in videos • Brain MRI • Kinect User Interface • 3D Aorta CT • Brain AVM 3D MRI 23 Visualization of Non-image Data • CAD rendering (computer aided design) • Elevation data rendering • 3D scanning • Visualization of abstract data 24 CAD Rendering 25 CAD Rendering Methods • Wireframe model • Hidden-line removal • Solid model • Tinted solid model 26 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 27 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 Methods 28 • In wireframe polygons can be seen as borderlines • In hidden-line removal lines behind the polygons are not drawn 29 Methods • Solid model rendering • Surface and color 30 Methods • Shaded solid model • A surface can also illustrate different materials such as metal or plastic 31 Texture and lighting • Images we create can look like real when we add different surfaces on them and illuminate them with multiple light sources 32 Photo-realistic Rendering • Materials, light refraction and reflections 33 Elevation data rendering 34 Elevation Model Reflection planes 35 The Calculation of A Reflectance 36 37 38 Example of Digital Terrain Model 39 40 3D-lightingModels 41 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 42 The Use of 3D Models • In industry 3D rendering before building an expensive prototype 43 The Use of 3D Models • Commercial use and entertainment industry • Games, movies and TV-programs 44 3D Examples • The features of the light can be rendered well, but this requires substantial computing power 45 3D Examples • The 3D- models have almost totally replaced the plastic models in the movie industry 47 Examples of 3D animation • Birth • 3DDentalPlanning • Fertilization