Abstract: Certain examples described herein relate to producing three-dimensional objects using additive manufacturing systems. These examples combine the use of material volume coverage vectors to define object data with octree data structures and models for tracking material placement error and available volumes. Material volume coverage vectors correspond to a volumes of three-dimensional objects and define a probabilistic distribution of materials available to an additive manufacturing system including combinations of said materials. In certain examples, a bottom level of the error tracking octree model is constructed to contain at least a portion of the data values for a set of obtained material volume coverage vectors. This is then used in an error distribution process to generate manufacturing control data for the additive manufacturing system.

Abstract: In an example, a method includes identifying, within data for use in printing, a first element set associated with a first print addressable area. The first element set may include at least one element, and each element of the set may be associated with a print material or print material combination. An element may be selected from the first element set and assigned to the first print addressable area. A second print addressable area may be identified as a candidate print addressable area for error diffusion, the second print addressable area being associated with a second element set. Any common elements of the first element set and the second element set may be identified and, if at least one common element is identified, an error associated with the selection of the element from the first element set may be diffused to the at least one common element.

Abstract: A color calibration chart may be created including a plurality of colors that are variations of a print color established for printing a reference color by a printing system using multiple colors. The colors in the calibration chart may be measured. A color from the calibration chart may be selected for printing the reference color which has a measurement value indicative of a color consistency within a predefined distance from a reference value for the print color.

Abstract: Methods and apparatus of determining a halftone scheme are described. In an example, data representing a three-dimensional object is obtained, the data comprising object model data representing the geometry of the three-dimensional object and object property data representing at least one object property of at least a portion of the object. It is determined if a halftone scheme dependent object property is specified by the object property data and a halftone scheme is determined. Data representing a portion of the object having a halftone scheme dependent object property is associated with a determined halftone scheme.

Abstract: An apparatus and method for use in generating calibration parameters for a printing apparatus comprising a plurality of print modules are disclosed. The method comprises printing a first plurality of test patches for each print module of the plurality of print modules, analysing the first plurality of test patches to identify at least two clusters of print modules, wherein each cluster comprises a sub-group of print modules having substantially similar performance, printing a second plurality of test patches comprising an extended calibration test patch set for each cluster of print modules, the second plurality of test patches being distributed across the print modules of the cluster, and analysing extended calibration test patch set for each cluster to determine a calibration parameter for the printing apparatus.

Abstract: In some examples, a system receives a color sample comprising a color measurement of a proper subset of a gamut of colors printable by a printer, and computes a forward transform value and a reverse transform value based on a color profile calculated from a profiling chart comprising a set of estimated color samples calculated based on the received color sample, the forward and reverse transform values to convert between colorimetry values and color values for the printer. The system provides an adjusted color profile for the printer based on an original color profile for the printer and the computing, wherein the original color profile for the printer is associated with a substrate.

Abstract: Certain examples described herein relate to the use of three-dimensional threshold matrices in the production of three-dimensional objects. In one case, data values for a three-dimensional matrix for use in halftoning are assigned based on a structural volume coverage representation. In certain described cases, the structural volume coverage representation defines a probabilistic distribution of at least two different structures available for the production of the three-dimensional object. A comparison is performed based on data values for the structural volume coverage representation. The output of the comparison is a data value to be assigned to the three-dimensional matrix. The resultant three-dimensional matrix is used in a halftoning operation to control a structure distribution in the three-dimensional object.

Abstract: Embodiments of the present invention provide a method of determining whether data exceeds a validity range of an operation, comprising dividing operation data indicative of a range of validity of the operation into a plurality of chunks, determining a partial convex hull for each of the plurality of chunks, determining a convex hull for the operation data based on the plurality of partial convex hulls, and determining whether the data exceeds the validity range of the operation data based on the convex hull.

Abstract: A three-dimensional halftoning method is disclosed, wherein a halftone matrix including values is provided and subdivided into a plurality of sub-matrices, each sub-matrix including values of the halftone matrix in a respective sub-range. For a current slice of a three-dimensional representation of an object, a sub-matrix of the plurality of sub-matrices of the halftone matrix is selected and halftoning of the current slice is performed using the selected sub-matrix. Furthermore, an additive manufacturing method and system are described.

Abstract: In an example, a processing apparatus includes an interface to receive data representing a three-dimensional object. The data includes an object description comprising object property data. The processing apparatus comprises a mapping module to map the object description to an object generation description which includes at least one print material instruction associated with a predetermined combination of print materials from a set of print materials. The mapping module includes a plurality of mapping resources and each mapping resource associates combinations of print materials from the set of print materials with values of at least one object property. At least one object property of one mapping resource is different to at least one object property of another mapping resource. The processing apparatus also includes a selection module to select, for at least part of the object, one of the plurality of mapping resources to carry out mapping of the object description.

Abstract: A method is described in which sets of corresponding colorimetric values are obtained. In a set, a colorimetric value is associated with a device color. A number of device colors are selected according to the color differences between colorimetric values associated with the same device color. A color calibration pattern is elaborated for a printer to be calibrated using the selected device colors and calibration is performed using the sets of colorimetric values.

Abstract: Certain methods of generating a color mapping are described. In one method, an output of a color halftone processing pipeline is processed so as to determine a set of Neugebauer Primary area coverage (NPac) values that are representative of the output of the color halftone processing pipeline. These NPac values are then used, together with knowledge of an original input image, to generating the color mapping.

Abstract: Methods and apparatus relating to previews of objects are described. In one example, control data for generating a three-dimensional object specifying, for voxels of the object, at least one print material to be deposited in that voxel during object generation is obtained. A viewing frustum may be determined, and visible voxels within the viewing frustum identified. A number of preview display pixels to display the preview may be determined and the set of voxels to be represented by each preview display pixel identified. At least one voxel appearance parameter of a voxel may be determined from the control data. For each preview display pixel, at least one pixel appearance parameter may be determined by combining voxel appearance parameters for the set of voxels to be represented by that preview display pixel. Preview display pixels may be controlled to display a preview of the object according to the at least one pixel appearance parameter.

Abstract: From a statistical distribution of different color states in an image subdivided in pixels, pixel color states are selected by performing comparisons between predetermined values and values associated to per-pixel state probabilities. Errors (based on drifts between selected color states and per-pixel state probabilities) are diffused to per-pixel state probabilities of subsequent pixels.

Abstract: Certain examples described herein relate to the use of three-dimensional threshold matrices in the production of three-dimensional objects. In one case, data values for a three-dimensional matrix for use in halftoning are assigned based on a structural volume coverage representation. In certain described cases, the structural volume coverage representation defines a probabilistic distribution of at least two different structures available for the production of the three-dimensional object. A convex combination of the at least two different structures is determined, based on data values of the structure volume coverage representation. A data value may be assigned to the three-dimensional matrix based on the convex combination determined. The resultant three-dimensional matrix is used in a halftoning operation to control a structure distribution in the three-dimensional object.

Abstract: A system includes a memory to store pre-computed boundary look-up tables (LUTs) for respective drop weight boundary classes of a printer having a plurality of colorants. Each pre-computed boundary LUT provides one Neugebauer Primary area coverage (NPac) for each node of the LUT in response to a device color input value that corresponds to each node. Measurement data stored in the memory represent measured drop weight values for the plurality of different colorants of the printer. A processor executes instructions that interpolate among the pre-computed LUTs based on the measured drop weight values to determine a proportional weighting of each of the pre-computed LUTs.

Abstract: Methods for configuring and calibrating a printing system are described. Configuring a printing system involves obtaining data for determining a reference print element in the printing system. The reference print element is then used to determine calibration data for a given print element. The calibration data is applied for the given print element to generate a print output.

Abstract: Certain examples described herein relate to the processing of object data corresponding to a three-dimensional object. First data corresponding to a first portion of the three-dimensional object and second data corresponding to a second portion of the three-dimensional object, separate from the first portion, are determined. The first data is halftoned using a first halftoning technique to generate control instructions for an apparatus to produce the first portion of the three-dimensional object. The second data is halftoned using a second halftoning technique to generate control instructions for the apparatus to produce the second portion of the three-dimensional object.

Abstract: In an example implementation, a method of multiple dispense technology 3D printing includes receiving digital model data representing an object. The method includes formatting the data into an Mvec (material vector) specification that includes an Mvec to specify a material component of a voxel. The Mvec can have an associated dispense technology (DT) index to identify one of multiple available dispense technologies for dispensing the material component.

Abstract: A processing apparatus is provided. The processing apparatus includes a controller to process information as part of a Halftone Area Neugebauer Separation printing process to use at least one opaque ink as a process colorant in combination with at least one further process colorant.