Diploma Thesis
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- 2006 (10) (remove)
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- Diploma Thesis (10) (remove)
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- Augmented Reality (1)
- Axis Aligned Bounding Box (AABB) (1)
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- Institut für Computervisualistik (10) (remove)
Die Leistungsfähigkeit moderner Graphikkarten steigt zur Zeit schneller an, als die von CPUs. Dabei kann diese Leistung nicht nur zur Darstellung von 3D Welten, sondern auch für allgemeine Berechnungen (GPGPU) verwendet werden. Diese Diplomarbeit untersucht daher, ob mit Hilfe der GPU Volumendaten schneller gefiltert werden können, als mit der CPU. Dies soll insbesondere am Beispiel von Rausch-Filtern, die auf Videosequenzen angewendet werden, untersucht werden. Dabei soll das Video als Volumen repräsentiert und mit Volumenfiltern gefiltert werden. So soll eine höhere Qualität und eine kürzere Berechnungszeit als mit herkömmlichen CPU und Frame-basierten Verfahren erreicht werden, insbesondere auch bei den z.Z. stark aufkommenden hochauflösenden HDTV-Standards. Das Framework soll jedoch nicht auf Videosequenz-Bearbeitung beschränkt sein, sondern so konzipiert werden, dass es z.B. in bestehende Volumenvisualisierungssysteme integriert werden kann. Das Ziel der Arbeit ist die Einarbeitung in die notwendigen theoretischen Grundlagen, daran anschließend die prototypische Implementierung des Frameworks mit abschließender Bewertung der erreichten Ergebnisse insbesondere der Geschwindigkeit im Vergleich zu existierenden Systemen.
Shadows add a level of realism to a rendered image. Furthermore, they support the user of an augmented reality application through the interactions of virtual objects. The reason for this is that shadows make it easier to judge the position and the size of a virtual object. In 1978, Lance Williams published the shadow mapping algorithm with the aim to render a shadow of objects in a virtual scene. This master thesis presents a modified shadow mapping approach that can additionally be used in Augmented/Mixed Reality applications. First of all the standard algorithm ist extended by a PCF-filter. This filter is used to handle the aliasing-problem on the edges of the shadow and also to soften the shadow. Phantom objects are necessary to be able to operate this approach in a Mixed Reality application. These objects simulate the position and the geometry of the real objects for the algorithm. The approach consists of three steps: First the camera image is drawn into the framebuffer. After that a shadow map, of the virtual objects only, is created. When rendering these objects shadow mapping creates the shadows of virtual objects onto other virtual objects and on themselves. Afterwards the phantom objects are rendered. The depth test is performed on the fragment shader. If a fragment lies in a shadowed region it will get the color of the shadow. However, if it is beeing lit its transpareny value will be set to 1 so that it will not be seen. By applying this procedure all shadows from the virtual objects onto the real objects will be drawn. The results show that the approach can be used in real time in Mixed Reality environments. Additionally a comparison with a modified version of a shadow volume algorithm that can also be used for Mixed Reality applications shows that the approach of this master thesis casts a more realistic shadow in a shorter period of time. All in all this approach increases the level of realism in augmented reality applications and it helps the user measure distances and sizes of the virtual objects more easily.
This work represents a quantitative analysis and visualisation of scar tissue of the left ventricular myocard. The scar information is shown in the late enhancement data, that highlights the avitale tissue with the help of a contrast agent. Through automatic methods, the scar is extracted from the image data and quantifies the size, location and transmurality. The transmurality shows a local measurement between the heart wall und the width of the scar. The developed methods help the cardiologist to analyse the measurement, the reason and the degree of the heart failure in a short time period. He can further control the results by several visual presentations. The deformation of the scar tissue over the heart cycle is implemented in another scientific work. A visual improvement of the deformation result which extracts the scar out of the data is aspired. The avital tissue is shown in a more comfortable way by eliminating the unnecessary image information and therefore improves the visual analysis of the pumping heart. Both methods show a detailed analysis of the scar tissue. This supports the clinic practical throughout the manual analysis.