Browsing by Subject "Ray Tracing"
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Item Open Access Polarization included geometry based channel modeling for MIMO systems(2008) Akkaya, KezibanMost of the studies in the literature about channel modeling do not include the polarization. Aiming to develop a more realistic geometric model including polarization, the channel characteristics are examined using measurement data. Each multipath in the measurement data is modeled with a scatterer. Locations of scatterers are determined in the geometry based single bounce model. Then, each scatterer is replaced by a thin impedance disc. Electrical properties, sizes and orientations of discs are obtained using physical optics approximation. Using the channel model, XPD characteristics of the environment are examined. As a result of this study, a channel model for characterizing the general scenarios as much as possible is developed.Item Open Access Right-triangular subdivision for texture mapping ray-traced objects(Springer, 1998) Akdemir, U.; Özgüç, B.; Güdükbay, Uğur; Selçuk, A.The introduction of global illumination and texture mapping enabled the generation of high-quality, realistic looking images of computer graphics models. We describe a fast and efficient 2D texture mapping algorithm that uses triangle-to-triangle mapping, taking advantage of mapping an arbitrary triangle to a right triangle. This requires fewer floating point operations for finding the 2D texture coordinates and little preprocessing and storage. Texture mapping is combined with ray tracing for better visual effects. A filtering technique alternative to area sampling is developed to avoid aliasing artifacts. This technique uses linear eye rays, and only one eye ray per pixel is fired. A uniform supersampling filtering technique eliminates aliasing artifacts at the object edges.Item Open Access Volume based texture mapping(1995) Salk, Gürkan'I'he most realistic and attractive computer generated images are usually those that contain a large arnount of visual complexity and detail. Texturing is a widely used way of adding visual complexity and detail to computer generated iniciges. Traditionally surface texturing was only used to simulate surface detail. In this thesis we generate textures dehiuid throughout a region of three-dimensional space and map those textures together with their geometric definition onto complex objects. The textured object is rendered volume based with a. backward mapping algorithm (ray tracing). Hence the texture aJfects the definition and the realism of the object. In rendering tlie scene, natural phenomena such cis dispersion and absorption of light is also incorporated.