Minghao Pan

Zhejiang University, Hang-hsien, Zhejiang Sheng, China

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Publications (7)12.37 Total impact

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    ABSTRACT: Fast rendering of dynamic scenes with natural illumination, all-frequency shadows and spatially varying reflections is important but challenging. One main difficulty brought by moving objects is that the runtime visibility update of dynamic occlusion is usually time-consuming and slow. In this paper, we present a new visibility sampling technique and show that efficient all-frequency rendering of dynamic scenes can be achieved by sampling visibility of dynamic objects in an adaptive and parallel way. First, we propose a two-level adaptive sampling scheme to distribute sample points spatially and compute visibility maps angularly on each sample point. Then, we present a parallel hemispherical distance transform to convert these visibility maps into spherical signed distance fields. Finally, using such a distance-based visibility representation, we integrate our visibility sampling algorithm in the all-frequency rendering framework for scenes with spatially varying BRDFs. With an entire GPU-based implementation, our algorithm enables interactive all-frequency rendering of moderate dynamic scenes with environment lighting and spatially varying reflectance.
    Computers & Graphics 02/2014; 38:374–381. DOI:10.1016/j.cag.2013.10.036 · 1.03 Impact Factor
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    ABSTRACT: This paper presents a new technique for real-time relighting of static scenes with all-frequency shadows from complex lighting and highly specular reflections from spatially-varying BRDFs. The key idea is to depict the boundaries of visible regions using piecewise linear functions, and convert the shading computation into double product integrals - the integral of the product of lighting and BRDF on visible regions. By representing lighting and BRDF with spherical Gaussians and approximating their product using Legendre polynomials locally in visible regions, we show that such double product integrals can be evaluated in an analytic form. Given the precomputed visibility, our technique computes the visibility boundaries on the fly at each shading point, and performs the analytic integral to evaluate the shading color. The result is a real-time all-frequency relighting technique for static scenes with dynamic, spatially-varying BRDFs, which can generate more accurate shadows than the state-of-the-art real-time PRT methods.
    07/2012; DOI:10.1109/TVCG.2012.152
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    ABSTRACT: Shadow maps sample scene visibility in the light source space and offer an efficient solution to generate hard shadows. However, they suffer from aliasing artifacts because of discretization errors, inadequate resolution and projection distortion. In this paper, we propose the shadow geometry map method, where a shadow depth map is augmented by storing geometry information about scenes. This leads to a new shadowrendering algorithm that combines a supersampling filter, a geometry-aware reconstruction kernel and an irregular sampling filter. Our method produces high quality alias-free and subpixel supersampling shadow rendering and retains the simplicity and the efficiency of shadow maps. We show that the algorithm pipeline is efficiently parallelized using current programmable graphics hardware and that our method is capable of generating high quality hard shadows.
    Sciece China. Information Sciences 06/2012; 56(6). DOI:10.1007/s11432-012-4696-2 · 0.70 Impact Factor
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    ABSTRACT: Abstract Solving aliasing artifacts is an essential problem in shadow mapping approaches. Many works have been proposed, however, most of them focused on removing the texel-level aliasing that results from the limited resolution of shadow maps. Little work has been done to solve the pixel-level shadow aliasing that is produced by the rasterization on the screen plane. In this paper, we propose a fast, sub-pixel antialiased shadowing algorithm to solve the pixel aliasing problem. Our work is based on the alias-free shadow maps, which is capable of computing accurate per-pixel shadow, and only incurs little cost to extend to sub-pixel accuracy. Instead of direct supersampling the screen space, we take facets to approximate pixels in shadow testing. The shadowed area of one facet is rapidly evaluated by projecting blocker geometry onto a supersampled 2D occlusion mask with bitmasks fusion. It provides a sub-pixel occlusion sampling so as to capture fine shadow details and features. Furthermore, we introduce the silhouette mask map that limits visibility evaluation to pixels only on the silhouette, which greatly reduces the computation cost. Our algorithm runs entirely on the GPU, achieving real-time performance and is an order of magnitude faster than the brute-force supersampling method to produce comparable 32× antialiased shadows.
    Computer Graphics Forum 10/2009; 28:1927-1934. DOI:10.1111/j.1467-8659.2009.01571.x · 1.60 Impact Factor
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    Rui Wang, Kun Zhou, Minghao Pan, Hujun Bao
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    ABSTRACT: This paper presents a GPU-based method for interactive global illumination that integrates complex effects such as multi-bounce indirect lighting, glossy reflections, caustics, and arbitrary specular paths. Our method builds upon scattered data sampling and interpolation on the GPU. We start with raytraced shading points and partition them into coherent shading clusters using adaptive seeding followed by k-means. At each cluster center we apply final gather to evaluate its incident irradiance using GPU-based photon mapping. We approximate the entire photon tree as a compact illumination cut, thus reducing the final gather cost for each ray. The sampled irradiance values are then interpolated at all shading points to produce rendering. Our method exploits the spatial coherence of illumination to reduce sampling cost. We sample sparsely and the distribution of sample points conforms with the underlying illumination changes. Therefore our method is both fast and preserves high rendering quality. Although the same property has been exploited by previous caching and adaptive sampling methods, these methods typically require sequential computation of sample points, making them ill-suited for the GPU. In contrast, we select sample points adaptively in a single pass, enabling parallel computation. As a result, our algorithm runs entirely on the GPU, achieving interactive rates for scenes with complex illumination effects.
    ACM Transactions on Graphics 07/2009; 28. DOI:10.1145/1531326.1531397 · 3.73 Impact Factor
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    ABSTRACT: In this paper, we introduce a new representation - radiance transfer fields (RTF) - for rendering interreflections in dynamic scenes under low frequency illumination. The RTF describes the radiance transferred by an individ- ual object to its surrounding space as a function of the incident radiance. An important property of RTF is its independence of the scene configuration, enabling interreflection computation in dynamic scenes. Secondly, RTFs naturally fit in with the rendering framework of precomputed shadow fields, incurring negligible cost to add in- terreflection effects. In addition, RTFs can be used to compute interreflections for both diffuse and glossy objects. We also show that RTF data can be highly compressed by clustered principal component analysis (CPCA), which not only reduces the memory cost but also accelerates rendering. Finally, we present some experimental results demonstrating our techniques.
    Computer Graphics Forum 09/2007; 26:485-493. DOI:10.1111/j.1467-8659.2007.01071.x · 1.60 Impact Factor
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    ABSTRACT: We present a visual simulation technique called appearance mani- folds for modeling the time-variant surface appearance of a material from data captured at a single instant in time. In modeling time- variant appearance, our method takes advantage of the key obser- vation that concurrent variations in appearance over a surface repre- sent different degrees of weathering. By reorganizing these various appearances in a manner that reveals their relative order with re- spect to weathering degree, our method infers spatial and temporal appearance properties of the material's weathering process that can be used to convincingly generate its weathered appearance at dif- ferent points in time. Results with natural non-linear reflectance variations are demonstrated in applications such as visual simula- tion of weathering on 3D models, increasing and decreasing the weathering of real objects, and material transfer with weathering effects. by global factors such as object geometry and weathering environ- ment, while small scale characteristics of a material are primarily determined by local factors such as physical material interactions with weather. The local variations in weathered appearance are of- ten intrinsic to the material, a natural characteristic of how it looks. In this work, we address the problem of how to generate convincing weathered appearance of a material on a D model over a period of time.
    ACM Transactions on Graphics 07/2006; 25:754-761. DOI:10.1145/1141911.1141951 · 3.73 Impact Factor