Abstract
We present a shape-from-shading approach for oblique lighting with accuracy enhancement by light direction optimization. Based on an application of the Jacobi iterative method to the consistency between the reflectance map and image, four surface normal approximations are introduced and the resulting four iterative relations are combined as constraints to get an iterative relation. The matrix that converts the shading information to the depth is modified so as to be uniform over the whole image region, making the iteration stable and, as a result, the resulting shape more accurate. Then, to enhance the accuracy, the light direction is optimized for slant angle using two criteria based on the initial boundary value and the rank of the converting matrix. The method is examined using synthetic and real images to show that it is superior to the current state-of-the-art methods and that it is effective for oblique light direction whose slant angle ranges from 55 to 75 degrees.
Highlights
Shape reconstruction from a single shading image has been studied for decades [1], producing a variety of approaches using minimization [2, 3], linearization [4], propagation [5, 6], deformable model [7], viscosity solutions [8,9,10,11], an attenuation term of the form 1/r2 [12], and the Helmholtz reciprocity [13] that uses the attenuation term
We present a novel shape-from-shading method, which uses neither adjusting parameters nor a priori or additional information, and which appears more accurate for oblique light cases than the current methods. In this method, based on an application of the Jacobi iterative method to the consistency between the image and the reflectance map, we introduce four surface normal approximations and the resulting four iterative relations are combined as constraints to get an iterative relation
We presented a shape-from-shading method for oblique lighting with accuracy enhancement by light direction optimization
Summary
Shape reconstruction from a single shading image has been studied for decades [1], producing a variety of approaches using minimization [2, 3], linearization [4], propagation [5, 6], deformable model [7], viscosity solutions [8,9,10,11], an attenuation term of the form 1/r2 [12], and the Helmholtz reciprocity [13] that uses the attenuation term. We present a novel shape-from-shading method, which uses neither adjusting parameters nor a priori or additional information, and which appears more accurate for oblique light cases than the current methods. In this method, based on an application of the Jacobi iterative method to the consistency between the image and the reflectance map, we introduce four surface normal approximations and the resulting four iterative relations are combined as constraints to get an iterative relation. In order to enhance the accuracy, the light direction is optimized using two criteria based on the initial boundary value in the iteration and the rank of the converting matrix
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