[
    {
        "id": "charalambos-thesis_hlod",
        "type_id": "phdthesis",
        "tu_id": null,
        "repositum_id": null,
        "title": "HLOD Refinement Driven by Hardware Occlusion Queries",
        "date": "2008-12",
        "abstract": "In order to achieve interactive rendering of complex models comprising several millions\r\nof polygons, the amount of processed data has to be substantially reduced. Level-ofdetail\r\n(LOD) methods allow the amount of data sent to the GPU to be aggressively\r\nreduced at the expense of sacrificing image quality. Hierarchical level-of-detail (HLOD)\r\nmethods have proved particularly capable of interactive visualisation of huge data sets\r\nby precomputing levels-of-detail at different levels of a spatial hierarchy. HLODs support\r\nout-of-core algorithms in a straightforward way and allow an optimal balance between\r\nCPU and GPU load during rendering.\r\nOcclusion culling represents an orthogonal approach for reducing the amount of rendered\r\nprimitives. Occlusion culling methods aim to quickly cull the invisible part of the\r\nmodel and render only its visible part. Most recent methods use hardware occlusion\r\nqueries (HOQs) to achieve this task.\r\nThe effects of HLODs and occlusion culling can be successfully combined. Firstly,\r\nnodes which are completely invisible can be culled. Secondly, HOQ results can be used\r\nfor visible nodes when refining an HLOD model; according to the degree of visibility of a\r\nnode and the visual masking perceptual phenomenon, then it could be determined that\r\nthere would be no gain in the final appearance of the image obtained if the node were\r\nfurther refined. In the latter case, HOQs allow more aggressive culling of the HLOD\r\nhierarchy, further reducing the amount of rendered primitives. However, due to the\r\nlatency between issuing an HOQ and the availability of its result, the direct use of HOQs\r\nfor refinement criteria cause CPU stalls and GPU starvation.\r\nThis thesis introduces a novel error metric, taking visibility information (gathered from\r\nHOQs) as an integral part of refining an HLOD model, this being the first approach\r\nwithin this context to the best of our knowledge. A novel traversal algorithm for HLOD\r\nrefinement is also presented for taking full advantage of the introduced HOQ-based error\r\nmetric. The algorithm minimises CPU stalls and GPU starvation by predicting HLOD\r\nrefinement conditions using spatio-temporal coherence of visibility.\r\nSome properties of the combined approach presented here involve improved performance\r\nhaving the same visual quality (whilst our occlusion culling technique still remained\r\nconservative). Our error metric supports both polygon-based and point-based\r\nHLODs, ensuring full use of HOQ results (our error metrics take full advantage of the\r\ninformation gathered in HOQs). Our traversal algorithm makes full use of the spatial\r\nand temporal coherency inherent in hierarchical representations. Our approach can be\r\nstraightforwardly implemented.",
        "authors_et_al": false,
        "substitute": null,
        "main_image": {
            "description": "",
            "filetitle": "image",
            "main_file": false,
            "use_in_gallery": false,
            "access": "public",
            "image_width": 1000,
            "image_height": 478,
            "name": "charalambos-thesis_hlod-image.png",
            "type": "image/png",
            "size": 134213,
            "path": "Publication:charalambos-thesis_hlod",
            "url": "https://www.cg.tuwien.ac.at/research/publications/2008/charalambos-thesis_hlod/charalambos-thesis_hlod-image.png",
            "thumb_image_sizes": [
                16,
                64,
                100,
                175,
                300,
                600
            ],
            "thumb_url": "https://www.cg.tuwien.ac.at/research/publications/2008/charalambos-thesis_hlod/charalambos-thesis_hlod-image:thumb{{size}}.png"
        },
        "sync_repositum_override": null,
        "repositum_presentation_id": null,
        "authors": [
            621
        ],
        "co_supervisor": [
            686
        ],
        "date_end": "2008",
        "rigorosum": "2008-02-20",
        "supervisor": [
            193
        ],
        "research_areas": [],
        "keywords": [],
        "weblinks": [],
        "files": [
            {
                "description": "",
                "filetitle": "image",
                "main_file": false,
                "use_in_gallery": false,
                "access": "public",
                "image_width": 1000,
                "image_height": 478,
                "name": "charalambos-thesis_hlod-image.png",
                "type": "image/png",
                "size": 134213,
                "path": "Publication:charalambos-thesis_hlod",
                "url": "https://www.cg.tuwien.ac.at/research/publications/2008/charalambos-thesis_hlod/charalambos-thesis_hlod-image.png",
                "thumb_image_sizes": [
                    16,
                    64,
                    100,
                    175,
                    300,
                    600
                ],
                "thumb_url": "https://www.cg.tuwien.ac.at/research/publications/2008/charalambos-thesis_hlod/charalambos-thesis_hlod-image:thumb{{size}}.png"
            },
            {
                "description": "",
                "filetitle": "paper",
                "main_file": true,
                "use_in_gallery": false,
                "access": "public",
                "name": "charalambos-thesis_hlod-paper.pdf",
                "type": "application/pdf",
                "size": 2553154,
                "path": "Publication:charalambos-thesis_hlod",
                "url": "https://www.cg.tuwien.ac.at/research/publications/2008/charalambos-thesis_hlod/charalambos-thesis_hlod-paper.pdf",
                "thumb_image_sizes": [
                    16,
                    64,
                    100,
                    175,
                    300,
                    600
                ],
                "thumb_url": "https://www.cg.tuwien.ac.at/research/publications/2008/charalambos-thesis_hlod/charalambos-thesis_hlod-paper:thumb{{size}}.png"
            }
        ],
        "projects_workgroups": [],
        "url": "https://www.cg.tuwien.ac.at/research/publications/2008/charalambos-thesis_hlod/",
        "__class": "Publication"
    },
    {
        "id": "CHARALAMBOS-2007-HLOD",
        "type_id": "inproceedings",
        "tu_id": null,
        "repositum_id": null,
        "title": "Optimized HLOD Refinement Driven by Hardware Occlusion Queries",
        "date": "2007-11",
        "abstract": "We present a new method for integrating hierarchical levels of detail (HLOD) with occlusion culling. The algorithm refines the HLOD hierarchy using geometric criteria as well as the occlusion information. For the refinement we use a simple model which takes into account the possible distribution of the visible pixels. The traversal of the HLOD hierarchy is optimized by a new algorithm which uses spatial and temporal coherence of visibility. We predict the HLOD refinement condition for the current frame based on the results from the last frame. This allows an efficient update of the front of termination nodes as well as an efficient scheduling of hardware occlusion queries.  Compared to previous approaches, the new method improves on speed as well as image quality. The results indicate that the method is very close to the optimal scheduling of occlusion queries for driving the HLOD refinement.",
        "authors_et_al": false,
        "substitute": null,
        "main_image": {
            "description": null,
            "filetitle": "",
            "main_file": false,
            "use_in_gallery": false,
            "access": "public",
            "image_width": 624,
            "image_height": 457,
            "name": "CHARALAMBOS-2007-HLOD-.png",
            "type": "image/png",
            "size": 8177,
            "path": "Publication:CHARALAMBOS-2007-HLOD",
            "url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-.png",
            "thumb_image_sizes": [
                16,
                64,
                100,
                175,
                300,
                600
            ],
            "thumb_url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-:thumb{{size}}.png"
        },
        "sync_repositum_override": null,
        "repositum_presentation_id": null,
        "authors": [
            621,
            198,
            193,
            686
        ],
        "booktitle": "Advances in Visual Computing (Third International Symposium on Visual Computing -- ISVC 2007)",
        "date_from": "2007-11-26",
        "date_to": "2007-11-28",
        "editor": "Bebis, G.; Boyle, R.; Parvin, B.; Koracin, D.; Paragios, N.; Tanveer, S.-M.; Ju, T.; Liu, Z.; Coquillart, S.; Cruz-Neira, C.; Möller, T.; Malzbender, T.",
        "isbn": "978-3-540-76855-9",
        "lecturer": [
            621
        ],
        "location": "Lake Tahoe, Nevada/California",
        "pages_from": "106",
        "pages_to": "117",
        "publisher": "Springer",
        "series": "Lecture Notes in Computer Science, volume 4841",
        "research_areas": [
            "Rendering"
        ],
        "keywords": [
            "occlusion queries",
            "levels of detail",
            "occlusion culling"
        ],
        "weblinks": [],
        "files": [
            {
                "description": null,
                "filetitle": "",
                "main_file": false,
                "use_in_gallery": false,
                "access": "public",
                "image_width": 624,
                "image_height": 457,
                "name": "CHARALAMBOS-2007-HLOD-.png",
                "type": "image/png",
                "size": 8177,
                "path": "Publication:CHARALAMBOS-2007-HLOD",
                "url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-.png",
                "thumb_image_sizes": [
                    16,
                    64,
                    100,
                    175,
                    300,
                    600
                ],
                "thumb_url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-:thumb{{size}}.png"
            },
            {
                "description": null,
                "filetitle": "Preprint",
                "main_file": true,
                "use_in_gallery": false,
                "access": "public",
                "name": "CHARALAMBOS-2007-HLOD-Preprint.pdf",
                "type": "application/pdf",
                "size": 1524313,
                "path": "Publication:CHARALAMBOS-2007-HLOD",
                "url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-Preprint.pdf",
                "thumb_image_sizes": [
                    16,
                    64,
                    100,
                    175,
                    300,
                    600
                ],
                "thumb_url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-Preprint:thumb{{size}}.png"
            },
            {
                "description": "Video for the paper",
                "filetitle": "video",
                "main_file": false,
                "use_in_gallery": false,
                "access": "public",
                "preview_image_width": 720,
                "preview_image_height": 576,
                "name": "CHARALAMBOS-2007-HLOD-video.avi",
                "type": "video/x-msvideo",
                "size": 46642670,
                "path": "Publication:CHARALAMBOS-2007-HLOD",
                "preview_name": "CHARALAMBOS-2007-HLOD-video:preview.png",
                "preview_type": "image/jpeg",
                "preview_size": 8215,
                "url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-video.avi",
                "thumb_image_sizes": [
                    16,
                    64,
                    100,
                    175,
                    300,
                    600
                ],
                "thumb_url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-video:thumb{{size}}.png",
                "video_mp4": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-video:video.mp4"
            },
            {
                "description": "Visualization of the error metric",
                "filetitle": "vis",
                "main_file": false,
                "use_in_gallery": false,
                "access": "public",
                "image_width": 2553,
                "image_height": 1381,
                "name": "CHARALAMBOS-2007-HLOD-vis.png",
                "type": "image/png",
                "size": 885003,
                "path": "Publication:CHARALAMBOS-2007-HLOD",
                "url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-vis.png",
                "thumb_image_sizes": [
                    16,
                    64,
                    100,
                    175,
                    300,
                    600
                ],
                "thumb_url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/CHARALAMBOS-2007-HLOD-vis:thumb{{size}}.png"
            }
        ],
        "projects_workgroups": [
            "GameTools"
        ],
        "url": "https://www.cg.tuwien.ac.at/research/publications/2007/CHARALAMBOS-2007-HLOD/",
        "__class": "Publication"
    }
]