| 1. |
- Akenine-Möller, Tomas, et al.
(författare)
-
Approximate Soft Shadows on Arbitrary Surfaces using Penumbra Wedges
- 2002
-
Ingår i: EGRW '02 Proceedings of the 13th Eurographics workshop on Rendering. - 1581135343 ; , s. 297-306
-
Konferensbidrag (refereegranskat)abstract
- Shadow generation has been subject to serious investigation in computer graphics, and many clever algorithms have been suggested. However, previous algorithms cannot render high quality soft shadows onto arbitrary, animated objects in real time. Pursuing this goal, we present a new soft shadow algorithm that extends the standard shadow volume algorithm by replacing each shadow quadrilateral with a new primitive, called the penumbra wedge. For each silhouette edge as seen from the light source, a penumbra wedge is created that approximately models the penumbra volume that this edge gives rise to. Together the penumbra wedges can render images that often are remarkably close to more precisely rendered soft shadows. Furthermore, our new primitive is designed so that it can be rasterized efficiently. Many real-time algorithms can only use planes as shadow receivers, while ours can handle arbitrary shadow receivers. The proposed algorithm can be of great value to, e.g., 3D computer games, especially since it is highly likely that this algorithm can be implemented on programmable graphics hardware coming out within the next year, and because games often prefer perceptually convincing shadows.
|
|
| 2. |
- Akenine-Möller, Tomas, et al.
(författare)
-
Graphics for the Masses: A Hardware Rasterization Architecture for Mobile Phones
- 2003
-
Ingår i: ACM Transactions on Graphics. - : Association for Computing Machinery (ACM). - 1557-7368 .- 0730-0301. ; 22:3, s. 801-808
-
Konferensbidrag (refereegranskat)abstract
- The mobile phone is one of the most widespread devices with rendering capabilities. Those capabilities have been very limited because the resources on such devices are extremely scarce; small amounts of memory, little bandwidth, little chip area dedicated for special purposes, and limited power consumption. The small display resolutions present a further challenge; the angle subtended by a pixel is relatively large, and therefore reasonably high quality rendering is needed to generate high fidelity images.To increase the mobile rendering capabilities, we propose a new hardware architecture for rasterizing textured triangles. Our architecture focuses on saving memory bandwidth, since an external memory access typically is one of the most energy-consuming operations, and because mobile phones need to use as little power as possible. Therefore, our system includes three new key innovations: 1) an inexpensive multisampling scheme that gives relatively high quality at the same cost of previous inexpensive schemes, II) a texture minification system, including texture compression, which gives quality relatively close to trilinear mipmapping at the cost of 1.33 32-bit memory accesses on average, III) a scanline-based culling scheme that avoids a significant amount of z-buffer reads, and that only requires one context. Software simulations show that these three innovations together significantly reduce the memory bandwidth. and thus also the power consumption.
|
|
| 3. |
- Askerdal, Örjan, 1973, et al.
(författare)
-
A Control Theory Approach for Analyzing the Effects of Data Errors in Safety-Critical Control Systems
- 2002
-
Ingår i: Pacific Rim International Symposium on Dependable Computing, 2002. Proceedings. 2002. - 0769518524 ; , s. 105-114
-
Konferensbidrag (refereegranskat)abstract
- Computers are increasingly used for implementing controlalgorithms in safety-critical embedded applications, such asengine control, braking control and flight surfacecontrol. Addressing the consequent coupling of control performancewith computer related errors, this paper develops a composite computerdependability/control theory methodology for analyzing the effectsdata errors have on control system dependability. The effect is measured as theresulting control error (defined as the difference between the desired value ofa physical property andits actual value). We use maximum bounds on this measure as the criterion forcontrol system failure (i.e., if the control error exceeds a certain threshold,the system has failed).In this paper we a) present suitable models of computer faults for analysis of control level effects andrelated analysis methods, and b) apply traditional control theoryanalysis methods for understanding the effects of data errors onsystem dependability. An automobile slip-control brake-system is used as an example showing the viability of our approach.
|
|
| 4. |
- Assarsson, Ulf, 1972, et al.
(författare)
-
A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware
- 2003
-
Ingår i: ACM Transactions on Graphics. - : Association for Computing Machinery (ACM). - 1557-7368 .- 0730-0301. ; 22:3, s. 511-520
-
Konferensbidrag (refereegranskat)abstract
- Most previous soft shadow algorithms have either suffered from aliasing, been too slow, or could only use a limited set of shadow casters and/or receivers. Therefore, we present a strengthened soft shadow volume algorithm that deals with these problems. Our critical improvements include robust penumbra wedge construction, geometry-based visibility computation, and also simplified computation through a four-dimensional texture lookup. This enables us to implement the algorithm using programmable graphics hardware, and it results in images that most often are indistinguishable from images created as the average of 1024 hard shadow images. Furthermore, our algorithm can use both arbitrary shadow casters and receivers. Also, one version of our algorithm completely avoids sampling artifacts which is rare for soft shadow algorithms. As a bonus, the four-dimensional texture lookup allows for small textured light sources, and, even video textures can be used as light sources. Our algorithm has been implemented in pure software, and also using the GeForce FX emulator with pixel shaders. Our software implementation renders soft shadows at 0.5-5 frames per second for the images in this paper. With actual hardware, we expect that our algorithm will render soft shadows in real time. An important performance measure is bandwidth usage. For the same image quality, an algorithm using the accumulated hard shadow images uses almost two orders of magnitude more bandwidth than our algorithm.
|
|
| 5. |
- Borge, M. J. G., et al.
(författare)
-
Beta-delayed multiparticle emission studies at ISOL-type facilities
- 2004
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 746, s. 243-243
-
Konferensbidrag (refereegranskat)abstract
- We report here on the recent beta-decay studies made at ISOL-type Facilities to determine the multiparticle breakup mechanism of excited states in light nuclei by studying them in full kinematics. In particular the results obtained for the A = 9 isobars and the breakup of the 12.7 MeV state in C-12 of unnatural parity are discussed. The breakup of the latter has been debated since more than a decade. Mirror beta transitions in the A = 9 chain are compared and a large asymmetry factor is deduced for the transitions to high excitation energy in Be-9 (11.8 MeV) and B-9 (12.2 MeV) fed in the beta-decay of Li-9 and C-9 respectively. It is shown that the asymmetry is not due to experimental problems or differences in the mechanisms of breakup or in the spin of the states. As no asymmetry is found in the gs to gs transition it must be due to the particular structure of these excited states. The controversy on the breakup mechanism of the 12.7 MeV state is resolved.
|
|
| 6. |
- Cederkäll, Joakim, et al.
(författare)
-
REX-ISOLDE - experiences from the first year of operation
- 2004
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 746, s. 17-17
-
Konferensbidrag (refereegranskat)abstract
- The Radioactive beam EXperiment (REX) at CERN-ISOLDE has been commissioned and the first experiments successfully completed during 2002 and 2003. The concept used for post-acceleration has proven to be flexible and the experimental program has therefore been extended during the past year. This paper relays some experiences drawn from using the machine in the current program and also conveys some plans for the future.
|
|
| 7. |
- Engdar, Ulf, et al.
(författare)
-
Investigation of the two-phase flow field of the GTX100 compressor inlet during off-line washing
- 2004
-
Ingår i: ASME Turbo Expo 2004: Power for Land, Sea, and Air. - 0791841693 ; 4, s. 509-518
-
Konferensbidrag (refereegranskat)abstract
- A modern gas turbine compressor, with its highly aerodynamically loaded blades, is sensitive to changes in profile shape and to surface roughness. Fouling is inevitable, despite highly efficient filtration systems. The remedy to this problem is washing. There are two different approaches, online or off-line washing. The off-line wash is the most effective one, whilst on-line washing only prolongs the interval between off-line washes. Most findings in this field are highly empirical, being based on some 50 years of industrial gas turbine operation. This paper is an investigation of the two-phase flow in the bellmouth of the compressor during off-line washing conditions. The unit under study was the GTX100 turbo-set. Computational fluid dynamics (CFD) is used in this paper to perform a detailed study of the flow field. The main emphasis has been on studying the characteristics of the injected spray used for cleaning of the compressor. The benefit of heating this fluid is of special interest, since if this heating can be avoided, the outage time for the off-line compressor wash can be shortened. To provide the CFD computations with accurate boundary conditions for the spray, laser-based measurements of a spray, originating from an authentic wash nozzle, have been conducted. The commercial CFD program Star-Cd has been used for all computations. The computations show that the water injected, regardless of its inlet temperature, is cooled down to ambient air temperature well before the spray reaches the inlet guide vanes. This indicates that heating of the wash fluid can be abolished. The airflow seems not to be to influenced by the injected fluid to any great extend.
|
|
| 8. |
|
|
| 9. |
- Kester, O., et al.
(författare)
-
Accelerated radioactive beams from REX-ISOLDE
- 2003
-
Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 204, s. 20-20
-
Konferensbidrag (refereegranskat)abstract
- In 2001 the linear accelerator of the Radioactive beam EXperiment (REX-ISOLDE) delivered for the first time accelerated radioactive ion beams, at a beam energy of 2 MeV/u. REX-ISOLDE uses the method of charge-state breeding, in order to enhance the charge state of the ions before injection into the LINAC. Radioactive singly-charged ions from the on-line mass separator ISOLDE are first accumulated in a Penning trap, then charge bred to an A/q
|
|
| 10. |
|
|
