Browsing by Author "Zahn, Sebastian"

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Open Access
Interactive ray tracing of solvent excluded surfaces
(2018) Zahn, Sebastian
Domain experts in fields concerned with the behavior of molecules, for example biochemists, employ simulations to study a molecule’s individual properties and mutual interactions with other molecules. To obtain an intuitive spatial understanding of the returned data of the simulations, various visualization techniques such as molecular surfaces can be applied on the data. The solvent excluded surface depicts the boundary between the molecule’s and a solvent’s occupied space and therefore the molecules accessibility for the solvent. Insight about a molecule’s potential for interaction such as reactions can be gained by studying the surface’s shape visually. Current implementations for the visualization of the surface usually utilize GPU ray casting to achieve the performance required to allow interactivity such as viewpoint changing. However, this makes implementation of physically motivated effects like ambient occlusion or global illumination difficult. If compute resources do not contain GPUs, which is often the case in compute clusters, expensive software rasterization has to be employed instead. As CPUs offer less parallelism compared to GPUs, overhead introduced by the overdraw of thousands of primitives should be avoided. To mitigate these issues, CPU visualization approaches resurfaced again in recent times. In this work, the solvent excluded surface is visualized interactively using the classic ray tracing approach within the OSPRay CPU ray tracing framework. The described implementation is able to compute and visualize the solvent excluded surface for datasets composed of millions of atoms. Additionally, the surface supports transparency rendering, which allows implementation of a cavity visualization method that uses ambient occlusion.
Open Access
Rendering of densely recorded light fields
(2016) Zahn, Sebastian
Light fields present an alternate approach for producing images of a high degree of realism, by capturing real world data in the form of images, or by traditional techniques like raytracing a synthetic scene. In both cases, the produced data can be utilized to render images from positions which were previously not recorded or with different camera parameters and configurations. The resolution and spatial density, at which such light fields are recorded, influence the mass of produced data that has to be handled. This work focuses on densely recorded light fields and attempts to produce synthesized images computed from the available data, defined by a camera moving through space. Synthesized cameras are also able to change their aperture size and focus setting. Rendered cameras behave according to the thin lens model. A method for extraction of relevant light field images is proposed. For rendering of the data, two different approaches are evaluated. The first approach collects rays which are present in the light field in synthetic sensor plates. In an alternative approach, rays are collected in a standard hash map, and rendered by constructing and querying a kd-tree. Both approaches yield a set of properties which make them useful in different scenarios, and can also be combined to an hybrid renderer. The proposed system is intended to run on several machines in parallel.