A safety system for identifying safe regions in a three-dimensional workspace including controlled machinery, the system comprising: a plurality of sensors distributed about the workspace, each of the sensors being associated with a grid of pixels for recording images of a portion of the workspace within a sensor field of view, the workspace portions partially overlapping with each other; a controller configured to: register the sensors with respect to each other so that the images obtained by the sensors collectively represent the workspace; generate a three-dimensional representation of the workspace as a plurality of volumes; for each sensor pixel having an intensity level above a threshold value, preliminarily marking as unoccupied volumes intercepted by a line-of-sight ray path through the pixel and terminating at an estimated distance from the associated sensor of an occlusion, marking as occupied the volumes corresponding to a terminus of the ray path, and marking as unknown any volumes beyond the occlusion along the ray path; for each sensor pixel having an intensity level below the threshold value, preliminarily marking as unknown all volumes intercepted by a line-of-sight ray path through the pixel and terminating at a boundary of the workspace; finally marking as unoccupied volumes that have been preliminarily marked at least once as unoccupied; and mapping one or more safe volumetric zones within the workspace, the volumetric zones being outside a safety zone of the machinery and including only volumes marked as unoccupied wherein the controller is responsive to real-time monitoring of the workspace by the sensors and is configured to alter operation of the machinery in response to an intrusion into the safety zone detected by the sensors. a plurality of sensors distributed about the workspace, each of the sensors being associated with a grid of pixels for recording images of a portion of the workspace within a sensor field of view, the workspace portions partially overlapping with each other; a controller configured to: register the sensors with respect to each other so that the images obtained by the sensors collectively represent the workspace; generate a three-dimensional representation of the workspace as a plurality of volumes; for each sensor pixel having an intensity level above a threshold value, preliminarily marking as unoccupied volumes intercepted by a line-of-sight ray path through the pixel and terminating at an estimated distance from the associated sensor of an occlusion, marking as occupied the volumes corresponding to a terminus of the ray path, and marking as unknown any volumes beyond the occlusion along the ray path; for each sensor pixel having an intensity level below the threshold value, preliminarily marking as unknown all volumes intercepted by a line-of-sight ray path through the pixel and terminating at a boundary of the workspace; finally marking as unoccupied volumes that have been preliminarily marked at least once as unoccupied; and mapping one or more safe volumetric zones within the workspace, the volumetric zones being outside a safety zone of the machinery and including only volumes marked as unoccupied wherein the controller is responsive to real-time monitoring of the workspace by the sensors and is configured to alter operation of the machinery in response to an intrusion into the safety zone detected by the sensors. register the sensors with respect to each other so that the images obtained by the sensors collectively represent the workspace; generate a three-dimensional representation of the workspace as a plurality of volumes; for each sensor pixel having an intensity level above a threshold value, preliminarily marking as unoccupied volumes intercepted by a line-of-sight ray path through the pixel and terminating at an estimated distance from the associated sensor of an occlusion, marking as occupied the volumes corresponding to a terminus of the ray path, and marking as unknown any volumes beyond the occlusion along the ray path; for each sensor pixel having an intensity level below the threshold value, preliminarily marking as unknown all volumes intercepted by a line-of-sight ray path through the pixel and terminating at a boundary of the workspace; finally marking as unoccupied volumes that have been preliminarily marked at least once as unoccupied; and mapping one or more safe volumetric zones within the workspace, the volumetric zones being outside a safety zone of the machinery and including only volumes marked as unoccupied wherein the controller is responsive to real-time monitoring of the workspace by the sensors and is configured to alter operation of the machinery in response to an intrusion into the safety zone detected by the sensors.