In this paper, we discuss an interpolation method which can be used to create a look up table to map tristimulus values to BRDF parameters. For a given tristimulus value, we interpolate the XYZ lattice formed by eight primaries and secondaries that were printed and measured, and their corresponding optimised BRDF parameters. The BRDF parameters are obtained by careful optimisation of the Ward model and Cook Torrance model with the BRDF measurements of these primaries. The interpolated BRDF parameters of nine test samples from the same printed samples were then evaluated against the optimised BRDF parameters and their reference BRDF measurements. The results show that, this simple and efficient interpolation method produces consistent BRDF parameters that preserves the diffuse colour of the input sample.
We introduce a new algorithm to reduce metal artifacts in computed tomography images when data is acquired using a single source spectrum. Our algorithm is a hybrid approach which corrects the sinogram vector followed by an iterative reconstruction. Many prior sinogram correction algorithms identify projection measurements that travel through areas with significant metal content, and remove those projections, interpolating their values for use in subsequent reconstruction. In contrast, our algorithm retains the information of random subsets of these metal-affected projection measurements, and uses an average procedure to construct a modified sinogram. To reduce the secondary artifacts created by this interpolation, we apply an iterative reconstruction in which the solution is regularized using a sparsifying transform. We evaluate our algorithm on simulated data as well as data collected using a medical scanner. Our experiments indicate that our algorithm reduces the extent of metal artifacts significantly, and enables accurate recovery of structures in proximity to metal.