| 摘要 |
A method for obtaining a hue value in a volume ray casting method is provided to remarkably shorten rendering time as compared with an existing method by dividing the ceiling and floor of each candidate cell into virtual sub-squares, calculating a scalar value and a gradient vector for each divided sub-square using bilinear interpolation, storing them in a data storage, fetching a scalar value and a gradient vector for the nearest sub-square to a sample point on a ray among the sub-squares belonging to the ceiling of a specific candidate cell and a scalar value and a gradient vector for the nearest sub-square to the sample point among the sub-squares belonging to the floor of the specific candidate cell from the data storage when the sample point is located within the specific candidate cell, performing linear interpolation for the fetched scalar values and gradient vectors, obtaining scalar values and gradient vectors for the sample point, and obtaining a hue value for the sample point using the obtained scalar values and gradient vectors. The control part divides the ceiling and floor of each candidate cell into virtual sub-squares, calculates scalar values and gradient vectors for the divided sub-squares respectively using bilinear interpolation, and stores them in a data storage(S10). When a sample point on a ray is located within a specific candidate cell, the control part fetches a scalar value and a gradient vector for the nearest sub-square to the sample point among the sub-squares belonging to the ceiling of the specific candidate cell and a scalar value and a gradient vector for the nearest sub-square to the sample point among the sub-squares belonging to the floor of the specific candidate cell from the data storage(S20). The control part performs linear interpolation for the fetched scalar values and gradient vectors and obtains scalar values and gradient vectors for the sample point(S30). Finally the control part obtains a hue value for the sample point using the obtained scalar values and gradient vectors(S40). |
