Abstract: A three-dimensional object may be generated. A controller may be to control an energy source to apply energy to a layer of build material on a support member or previous layer to cause a portion of the layer to coalesce and solidify to form a slice of the three-dimensional object. A radiation sensor may be to measure absorbance or gloss of the layer. The controller may be to receive, from the radiation sensor, data representing measured absorbance or measured gloss of the layer. The controller may be to control the apparatus to modify a process parameter if the measured absorbance or gloss indicates an incorrect degree of solidification of a part of the layer.

Abstract: A three-dimensional object may be generated. Coalescing agent may be selectively delivered on a portion of a first layer of build material on a support member or previous layer. Energy may be applied to the first layer to cause the portion of the first layer to coalesce and solidify. A second layer of the build material may be provided on the first layer. While the second layer does not have coalescing agent delivered thereon, energy may be applied to the second layer such that energy may propagate through the second layer to the first layer to cause the portion of the first layer to coalesce and further solidify.

Abstract: In an example, an apparatus for generating a three-dimensional object includes a build area platform, a build material distributor, a secondary material ejection device, a coalescing agent ejection device, and a controller. The controller may control the secondary material ejection device to eject a secondary material in a predefined pattern over the build area platform, control the build material distributor to distribute a layer of the build material around the ejected secondary material, control the coalescing agent ejection device to eject the coalescing agent onto the layer of the build material, and control an energy source to apply energy onto the ejected coalescing agent to cause the build material in contact with the ejected coalescing agent to coalesce and solidify.

Abstract: A three-dimensional object may be generated. Coalescing agent may be selectively delivered on a portion of a first layer of build material on a support member or previous layer. Energy may be applied to the first layer to cause the portion of the first layer to coalesce and solidify. A second layer of the build material may be provided on the first layer. While the second layer does not have coalescing agent delivered thereon, energy may be applied to the second layer such that energy may propagate through the second layer to the first layer to cause the portion of the first layer to coalesce and further solidify.

Abstract: A three-dimensional object may be generated. Coalescing agent may be selectively delivered on a portion of a first layer of build material on a support member or previous layer. Energy may be applied to the first layer to cause the portion of the first layer to coalesce and solidify. A second layer of the build material may be provided on the first layer. While the second layer does not have coalescing agent delivered thereon, energy may be applied to the second layer such that energy may propagate through the second layer to the first layer to cause the portion of the first layer to coalesce and further solidify.

Abstract: Agent calibration can, in an example implementation, include generating a calibration based on a quantity of energy absorbed by a build material treated with different quantities of an agent and converting a portion of a three-dimensional object model to a quantity of agent based on the calibration.

Abstract: A method of forming a three-dimensional object includes non-deterministically generating halftone data for portions of a slice of three-dimensional model data of the three-dimensional object that overlap with a previous slice. The non-deterministically generating halftone data may comprise using randomized initialization for each slice of a three-dimensional object.

Abstract: Adjustment of a halftoning threshold can, in an example implementation, include assigning a relative energy value, relative to a reference energy value, to a location of a build area and adjusting a halftoning threshold based on the relative energy value.

Abstract: In a computational modeling method for identifying how to apply a modifying agent during a three-dimensional (3D) printing method, a thermal diffusion model of a layer of a 3D object to be formed from a portion of a sinterable material using the 3D printing method is created. The thermal diffusion model is created by a computer running computer readable instructions stored on a non-transitory, tangible computer readable storage medium. A quantity of the modifying agent to be selectively applied is calculated, by the computer, based upon the thermal diffusion model.

Abstract: A method of diffusing an error in three-dimensional contone model data includes generating halftone data for a slice among a number of slices of the three-dimensional contone model data, generating compensatory error values based on the generated halftone data, and adding the generated compensatory error values to contone data for a successive slice.

Abstract: An additive manufacturing system may include a controller to determine an emissivity of a portion of a layer of build material based on a measured optical property of the portion, or based on object design data representing a degree of intended solidification of the portion. The controller may be to determine a temperature of the portion based on the determined emissivity and a measured radiation distribution emitted by the portion.

Abstract: Agent calibration can, in an example implementation, include generating a calibration based on a quantity of energy absorbed by a build material treated with different quantities of an agent and converting a portion of a three-dimensional object model to a quantity of agent based on the calibration.

Abstract: Adjustment of a halftoning threshold can, in an example implementation, include assigning a relative energy value, relative to a reference energy value, to a location of a build area and adjusting a halftoning threshold based on the relative energy value.

Abstract: In an example, an apparatus for generating a three-dimensional object includes a build area platform, a build material distributor, a secondary material ejection device, a coalescing agent ejection device, and a controller. The controller may control the secondary material ejection device to eject a secondary material in a predefined pattern over the build area platform, control the build material distributor to distribute a layer of the build material around the ejected secondary material, control the coalescing agent ejection device to eject the coalescing agent onto the layer of the build material, and control an energy source to apply energy onto the ejected coalescing agent to cause the build material in contact with the ejected coalescing agent to coalesce and solidify.

Abstract: A method of diffusing an error in three-dimensional contone model data includes generating halftone data for a slice among a number of slices of the three-dimensional contone model data, generating compensatory error values based on the generated halftone data, and adding the generated compensatory error values to contone data for a successive slice.

Abstract: A method of forming a three-dimensional object includes non-deterministically generating halftone data for portions of a slice of three-dimensional model data of the three-dimensional object that overlap with a previous slice. The non-deterministically generating halftone data may comprise using randomized initialization for each slice of a three-dimensional object.

Abstract: In a computational modeling method for identifying how to apply a modifying agent during a three-dimensional (3D) printing method, a thermal diffusion model of a layer of a 3D object to be formed from a portion of a sinterable material using the 3D printing method is created. The thermal diffusion model is created by a computer running computer readable instructions stored on a non-transitory, tangible computer readable storage medium. A quantity of the modifying agent to be selectively applied is calculated, by the computer, based upon the thermal diffusion model.

Abstract: An additive manufacturing system may include a controller to determine an emissivity of a portion of a layer of build material based on a measured optical property of the portion, or based on object design data representing a degree of intended solidification of the portion. The controller may be to determine a temperature of the portion based on the determined emissivity and a measured radiation distribution emitted by the portion.

Abstract: A three-dimensional object may be generated. Coalescing agent may be selectively delivered on a portion of a first layer of build material on a support member or previous layer. Energy may be applied to the first layer to cause the portion of the first layer to coalesce and solidify. A second layer of the build material may be provided on the first layer. While the second layer does not have coalescing agent delivered thereon, energy may be applied to the second layer such that energy may propagate through the second layer to the first layer to cause the portion of the first layer to coalesce and further solidify.

Abstract: A three-dimensional object may be generated. A controller may be to control an energy source to apply energy to a layer of build material on a support member or previous layer to cause a portion of the layer to coalesce and solidify to form a slice of the three-dimensional object. A radiation sensor may be to measure absorbance or gloss of the layer. The controller may be to receive, from the radiation sensor, data representing measured absorbance or measured gloss of the layer. The controller may be to control the apparatus to modify a process parameter if the measured absorbance or gloss indicates an incorrect degree of solidification of a part of the layer.