173 results about "Spherical harmonics" patented technology

The present invention is directed to systems and methods for all-frequency relighting by representing low frequencies of lighting with spherical harmonics and approximate the residual high-frequency energy with point lights. One such embodiment renders low-frequencies with a precomputed radiance transfer (PRT) technique (which requires only a moderate amount of precomputation and storage), while the higher-frequencies are rendered with on-the-fly techniques such as shadow maps and shadow volumes. In addition, various embodiments are directed to a systems and methods for decomposing the lighting into harmonics and sets of point lights. Various alternative embodiments are directed to systems and methods for characterizing the types of environments for which the described decomposition is a viable technique in terms of speed (efficiency) versus quality (realism).

Methods and systems for processing audio data, such as spatial audio data, in which one or more sound characteristics of a given component of a spatial audio signal are modified in dependence on a relationship between a direction characteristic of the given component and a defined range of direction characteristics; this enhances the listening experience of the listener. A spatial audio in a format using a spherical harmonic representation of sound components is decoded by performing a transform on the spherical harmonic representation, in which the transform is based on a predefined speaker layout and a predefined rule, the predefined rule indicating a speaker gain of each speaker arranged according to the predefined layout, when reproducing sound incident form a given direction; this provides an alternative to existing method of decoding spatial audio streams, which focus on soundfield reconstruction. A plurality of matrix transforms is combined into a combined transform, and the combined transform is performed on an audio signal; this saves processing resources of the audio system being used.

Techniques of making a recording of or transmitting a sound field from either multiple monaural or directional sound signals that reproduce through multiple discrete loud speakers a sound field with spatial harmonics that substantially exactly match those of the original sound field. Monaural sound sources are positioned during mastering to use contributions of all speaker channels in order to preserve the spatial harmonics. If a particular arrangement of speakers is different than what is assumed during mastering, the speaker signals are rematrixed at the home, theater or other sound reproduction location so that the spatial harmonics of the sound field reproduced by the different speaker arrangement match those of the original sound field. An alternative includes recording or transmitting directional microphone signals, or their spatial harmonic components, and then matrixing these signals at the sound reproduction location in a manner that takes into account the specific speaker arrangement. The techniques are described for both a two dimensional sound field and the more general three dimensional case, the latter based upon using spherical harmonics.

Spatial encoding in magnetic resonance imaging (MRI) techniques is achieved by sampling the signal as a function of time in the presence of magnetic field gradients, e.g., X, Y, and Z gradients. The gradient magnets have in the past been assumed to generate a linear gradient, and typical image reconstruction techniques have relied upon this assumption. However, to achieve high speed performance, gradient magnets often sacrifice linearity for speed. This non-linearity, in turn, results in distorted images, the distortion often being sufficiently large to compromise the usefulness of MRI images for stereotaxy or longitudinal studies, where precise volumetric information is required. The disclosure provides practical methods for correcting distorted images resulting from such non-linearity in the gradient fields, as well as distortions resulting from translational, rotational, and/or winding/design errors in the field generating devices. The methods employ spherical harmonic expansions of the gradient fields and fast Fourier transform techniques to provide well-corrected images without undue computational burdens.

A rendering apparatus for real-time global illumination and a method thereof are disclosed. The rendering apparatus includes: a spherical harmonic processor for creating light samples and creating spherical harmonics basis functions; a light model processor for transforming radiance of a HDRI image to spherical harmonics light coefficients using the spherical harmonic basis functions; a radiance transfer processor for previously calculating coefficients of a visibility and a geometric term for a global illumination model using the spherical harmonic basis function; a BRDF processor for generating a database of BRDF data and calculating coefficients of the BRDF data through smoothing; and a render unit for rendering the spherical harmonic light coefficients, the coefficients for the visibility and the geometric term, and the BRDF data coefficient using a rendering equation expressed as a dot product of a vector.

Soundfield signals such as e.g. Ambisonics carry a representation of a desired sound field. The Ambisonics format is based on spherical harmonic decomposition of the soundfield, and Higher Order Ambisonics uses spherical harmonics of at least 2^nd order. However, commonly used loudspeaker setups are irregular and lead to problems in decoder design, A method for improved decoding an audio soundfield representation for audio playback comprises calculating a panning function using a geometrical method based on the positions of a plurality of loudspeakers and a plurality of source directions, calculating a mode matrix from the loudspeaker positions, calculating a pseudo-inverse mode matrix and decoding the audio soundfield representation. The decoding is based on a decode matrix that is obtained from the panning function and the pseudo-inverse mode matrix.

The invention discloses a multi-sound-source locating method based on a spherical microphone array, and the method comprises the following steps of firstly conducting spherical harmonics decomposition for high-order sound fields collected by a spherical microphone array, and building a noise-contained sound source signal model received by a spherical harmonics domain array; then expressing a covariance matrix of data received by the array; classifying the covariance matrix according to a subspace decomposition method to obtain two mutually-orthogonal signal subspace and noise subspace; utilizing the orthogonality of the signal subspace and the noise subspace to define a guide vector of the signal subspace, and extracting one characteristic vector of the noise subspace to build a space azimuth spectrum; and finally searching a spectrum peak position of an azimuth spectrum function, and determining a space azimuth of a sound source. The method utilizes a three-dimensional space rotary symmetric structure of the spherical microphone array to adequately sample the sound field, so that the operation quantity is remarkably reduced through the high-resolution spectrum estimation and dimensional-reduced noise subspace, the sound source azimuth is accurately estimated, and the method can be widely applied to the fields such as a voice signal processing field.

The invention concerns the processing of audio data. The invention is characterized in that it consists in: (a) encoding signals representing a sound propagated in three-dimensional space and derived from a source located at a first distance (P) from a reference point, to obtain a representation of the sound through components expressed in a spherical harmonic base, of origin corresponding to said reference point, (b) and applying to said components compensation of a near-field effect through filtering based on a second distance (R) defining, for sound reproduction, a distance between a reproduction point (HP_i), and a point (P) of auditory perception where a listener is usually located.

An apparatus to measure surface orientation maps of an object may include a light source that is configured to illuminate the object with a controllable field of illumination. One or more cameras may be configured to capture at least one image of the object. A processor may be configured to process the image(s) to extract the reflectance properties of the object including an albedo, a reflection vector, a roughness, and/or anisotropy parameters of a specular reflectance lobe associated with the object. The controllable field of illumination may include limited-order Spherical Harmonics (SH) and Fourier Series (FS) illumination patterns with substantially similar polarization. The SH and FS illumination patterns are used with different light sources.

A method for sensing touch inputs to a digital equipment is provided, comprising the steps of sensing a sound/vibration signal generated by a touch, digitally processing the sensed sound/vibration signal, and determining the type of touch means that has generated the touch and the intensity of the touch based on the properties of the processed sound/vibration signal, wherein the properties include at least one of the following properties of the sound/vibration signal in time domain: maximum amplitude, average amplitude, average frequency, mean, standard deviation, standard deviation normalized by overall amplitude, variance, skewness, kurtosis, sum, absolute sum, root mean square (RMS), crest factor, dispersion, entropy, power sum, center of mass, coefficients of variation, cross correlation, zero-crossings, seasonality, DC bias, or the above properties computed for the first, second, third or higher order of derivatives of the sound/vibration signal; and the following properties of the sound/vibration signal in frequency domain: spectral centroid, spectral density, spherical harmonics, total average spectral energy, band energy ratios for every octave, log spectral band ratios, linear prediction-based cepstral coefficients (LPCCs), perceptual linear prediction (PLP) cepstral coefficients, mel-frequency cepstral coefficients, frequency topology, or the above properties computed for the first, second, third or higher order of derivatives of a frequency domain representation of the sound/vibration signal. There is also provided a device for sensing touch inputs.

A computer aided diagnostic system and automated method diagnose lung cancer through modeling and analyzing the shape of pulmonary nodules. A model used in such analysis describes the shape of pulmonary nodules in terms of spherical harmonics required to delineate a unit sphere corresponding to the pulmonary nodule to a model of the pulmonary nodule.

A method generating a virtual audio signal for a listener. The method includes estimating spherical harmonic coefficients based on an individual character of the listener. The estimated spherical harmonic coefficients are compared to a distribution of known spherical harmonic coefficients. The estimated spherical harmonic coefficients are iteratively updated and compared to the distribution of known spherical harmonic coefficients until convergence. The individual character and the converged spherical harmonic coefficients are then applied to a mono-channel sound.

A computer software program is described that maps the electrical activity of a patient's heart. The software program utilizes inputs from electrodes contained within a heart chamber. Inputs from the electrodes cause the program to calculate the heart chamber volume, and then to determine the position of the electrodes within the heart chamber. The program then utilizes inputs from the electrodes to calculate the three-dimensional volumetric electrical field distribution of said heart chamber. This calculation is accomplished using a spherical harmonic series expression. Finally, the computer program displays the electrical field distribution of the heart chamber.

A sound capture device comprises a symmetric microphone array that includes non-radially-oriented directional sensors (101). The device typically derives a spherical harmonic representation of the incident sound field, and affords higher signal-to-noise ratios and better directional fidelity than prior arrays, across a wide range of audio frequencies.

Computer graphics image rendering techniques render images using a precomputed radiance transfer (PRT) to model local effects such as bumps, wrinkles, or other detailed features on an arbitrarily deformable model's surface. The techniques apply zonal harmonics (ZH) which approximate spherical functions as sums of circularly symmetric functions around different axes. By spatially varying both the axes and coefficients of these basis functions, approximations can fit to spatially varying transfer signals. Compared to the spherical harmonic (SH) basis, the ZH basis yields a more compact approximation, and can be rotated at a low computational expense suitable for dense per-vertex or per-pixel evaluation. This allows PRT to be mapped onto deforming models which re-orient the local coordinate frame.

The invention relates to a small celestial body attachment detection descending trajectory optimization method, and belongs to the field of aviation and aerospace. According to the method, an internal spherical harmonic gravitational field model is adopted for estimating gravitational acceleration near a target small celestial body, and a convex optimization algorithm is adopted for solving the optimal control problem. By adopting the internal spherical harmonic gravitational field model for estimating the gravitational acceleration near the target small celestial body, the advantage of being high in computational efficiency is achieved. By adopting the convex optimization algorithm for solving the optimal fuel control problem, the problems that derivation of a indirection method is complicated, and co-state variables are free of physical meaning and not likely to guess are avoided, the derivation step is simple, the computing time is saved, the estimation optimization method is rapid and high in precision, and the obtained result conforms to initial and end state constraint, dynamic constraint and control constraint.

The invention provides a method and device for determining a global ionized layer grid model, belongs to the field of global navigation systems and space environment monitoring, and is used for solving the problems that systematic bias exists among various ionized layer data, and the various ionized layer data cannot be fused in a simple manner. The method includes determining an ionized layer VTEC1 in a zenith direction through formulae (1) and (2) according to GNSS observed data; adopting a formula (3) and combined with a smooth and resampling method to obtain an ionized layer VTEC2 in the zenith direction according to data of ocean height-measuring satellites; according to a double-frequency phase observed value of a DORIS, determining STEC<bias> through a formula (4), through a GIM interpolation principle, the double-frequency phase observed value of the DORIS and the STEC<bias>, determining corrected STEC, and determining an ionized layer VTEC3 in the zenith direction according to the corrected STEC and a calibration method; and performing fitting on the ionized layers VTEC1, VTEC2 and VTEC3 according to a spherical harmonics model, and determining the global ionized layer grid model based on multi-source data fusion.

The invention discloses a coronary artery CT (computed tomography) contrastographic image calcification point detecting method. According to the method, the existing coronary artery central axis is utilized, firstly, the local structural features of each voxel point in an interested region of a blood vessel are extracted, then, the spherical harmonic conversion is utilized for quantizing the local structural features, feature vectors are obtained, finally, a classification algorithm is adopted for classifying the obtained feature vectors, the local structural feature approximation degree of the voxel points to the calcification points, blood vessel lomens and image backgrounds in a training dataset is determined, and calcification point detecting results are finally obtained. The method has the advantages that calcification points positioned on the coronary artery blood vessel walls in the coronary artery CT contrastographic image can be precisely positioned, and the efficiency and the accurate rate of the computer auxiliary diagnosis are improved.

Real-time processing includes per-point transfer matrices forming a high-dimensional surface signal that is compressed using clustered principal component analysis (CPCA). CPCA partitions multiple samples into fewer clusters, each cluster approximating the signal as an affine subspace. Further, source radiance is input to a processor, which approximates source radiance using spherical harmonic basis to produce a set of source radiance coefficients. A graphics processing unit (GPU) processes the source radiance coefficients through the transfer matrix model for each cluster. The result of such processing is the exit radiance, which parameterizes the radiance leaving the surface of the object at each point, thus producing the shading for each point of the virtual object in real time.

A system and process for determining the similarity in the shape of objects is presented that generates a novel shape representation called a directional histogram model. This shape representative captures the shape variations of an object with viewing direction, using thickness histograms. The resulting directional histogram model is substantially invariant to scaling and translation. A matrix descriptor can also be derived by applying the spherical harmonic transform to the directional histogram model. The resulting matrix descriptor is substantially invariant to not only scaling and translation, but rotation as well. The matrix descriptor is also robust with respect to local modification or noise, and able to readily distinguish objects with different global shapes. The typical applications of the directional histogram model and matrix descriptor include recognizing 3D solid shapes, measuring the similarity between different objects and shape similarity based object retrieval.

The method of correcting gradient deformation of magnetic resonant image based on spherical harmonic function includes three steps of calculating spatial offset, compensating correction of image offset and searching correction of parameters. The 3D offset of each pixel in the 3D image is calculated based on the spherical harmonic function of magnetic induction intensity, and compensated to the image coordinate of the pixel. The present invention has high algorithm converging speed and high correction precision, and may be used widely magnetic resonant image led surgical treatment.

The invention discloses a GNSS ionization layer delay precise modeling method suitable for a Chinese region. The geographical coordinates of the latitude and the longitude of a cross point are converted into coordinates under an established spherical crown coordinate system, so as to acquire the range of the latitude and the longitude of the cross point under the spherical crown coordinate system. The change range of the latitude and the longitude of the cross point is projected and converted into a global coordinate system. A spherical harmonic function is used to establish a regional ionization layer total electron content (TEC) model. The ionization layer delay precise modeling method suitable for the Chinese region is constructed. Compared with the existing method, the method provided by the invention has the advantages that through rotation projection and conversion, the distribution of the ionization layer cross point meets the requirement of the spherical harmonic function on physical quantity distribution in the form; ill-conditioned problems are solved when the spherical harmonic function is applied to regional modeling; the precise describing ability of the spherical harmonic function for global change physical quantity is effectively used; non-integral order in a spherical crown harmonic function is avoided; and the complexity of ionization layer TEC modeling calculation is reduced.