Abstract: According to examples, an apparatus may include a processor and a non-transitory computer readable medium on which is stored instructions that may cause the processor to create a 2D reference mesh for an image of a curved visual mark, establish correspondences between finder pattern points in the curved visual mark and points of the 2D reference mesh, and determine a curved 3D mesh having a radius that results in a minimal reprojection error of a projective transform estimated for correspondences between the 2D reference mesh and the curved 3D mesh while the radius remains below a predefined upper limit. The instructions may also cause the processor to sample components of the curved visual mark in elements of the determined curved 3D mesh to form a 2D planar image of the curved visual mark and analyze the 2D planar image of the curved visual mark to read the curved visual mark.

Abstract: An example of a non-transitory computer-readable medium storing machine-readable instructions. The instructions may cause the processor to receive a three-dimensional (3D) object representation and subdivide it into a triangular grid. Curved triangles may be calculated for triangles in the triangular grid. The triangles may be subdivided and differences calculated between corresponding sections of the curved triangles and the received 3D object representation.

Abstract: An example of a computer-readable medium is provided to store machine-readable instructions. The instructions may cause a processor to receive three-dimensional (3D) object representations of an object. The distance between points of a grid applied to 3D object representation and random points on the 3D object representation may provide a sampling error used in calculating a modeling accuracy between the 3D object representations.

Abstract: An example of a non-transitory computer-readable medium storing machine-readable instructions. The instructions may cause the processor to receive a three-dimensional (3D) object representation and subdivide it into a triangular grid. Curved triangles may be calculated for triangles in the triangular grid. The triangles may be subdivided and differences calculated between corresponding sections of the curved triangles and the received 3D object representation.

Abstract: According to examples, an apparatus may include a processor and a memory on which is stored machine readable instructions executable by the processor to: identify a slice height for direct slicing of a Non-Uniform Rational B-Spline (NURBS) model formed of surfaces by slicing planes. The instructions may cause the processor to slice the NURBS model to produce slices having the identified slice height and to adaptively sub-divide surfaces of the NURBS model whose bounding boxes respectively intersect at least one of the slicing planes until the bounding boxes meet a predefined criterion. In addition, for each of the generated bounding boxes which meet the predefined criterion, the instructions may further cause the processor to determine sample points of the surface with which the bounding box corresponds and to store the sample points of the surfaces for printing.

Abstract: According to examples, an apparatus may include a processor and a non-transitory computer readable medium on which is stored instructions that may cause the processor to create a 2D reference mesh for an image of a curved visual mark, establish correspondences between finder pattern points in the curved visual mark and points of the 2D reference mesh, and determine a curved 3D mesh having a radius that results in a minimal reprojection error of a projective transform estimated for correspondences between the 2D reference mesh and the curved 3D mesh while the radius remains below a predefined upper limit. The instructions may also cause the processor to sample components of the curved visual mark in elements of the determined curved 3D mesh to form a 2D planar image of the curved visual mark and analyze the 2D planar image of the curved visual mark to read the curved visual mark.

Abstract: An example of a computer-readable medium is provided to store machine-readable instructions. The instructions may cause a processor to receive three-dimensional (3D) object representations of an object. The distance between points of a grid applied to 3D object representation and random points on the 3D object representation may provide a sampling error used in calculating a modeling accuracy between the 3D object representations.