A computer-implemented method for improving accuracy of a computer simulation of an original posture of a digital human model relative to a target object, comprising: providing, by a user, a precision level that represents a level of precision required for the DHM to perform a task associated with the target object; obtaining information associated with the original DHM posture, the obtained DHM posture information including a position of a head of the DHM; obtaining information associated with the target object, the obtained target object information including a size of the target object and an orientation of the target obj ect; obtaining a distance from the head of the DHM to the target object; generating a measure of vision of the DHM of the target object that the DHM is visually targeting, based on one or more parameters which include the obtained DHM posture information, the obtained target object information, and the obtained head-target distance; based on the measure of vision and on the precision level, generating a constraint of vision of the DHM to the target object, the constraint of vision representing an ability of the DHM to perform a task associated with the target object; based on the vision constraint, generating an updated DHM posture; and using the updated DHM posture to evaluate a risk of injury of a human and to properly size an environment around humans of different anthropometries; wherein the updated DHM posture provides an increased ability of the DHM to perform the task associated with the target object as compared with an ability of the DHM to perform the task associated with the target object using the original DHM posture, wherein the updated DHM posture is further generated based on an inverse kinematics engine and degrees of freedom of the DHM, and the inverse kinematic engine receives the vision constraint and determines the degrees of freedom of the DHM; wherein the vision constraint further represents a measure of closeness of the DHM to the target object, and the updated DHM posture is further generated based on the measure of closeness of the DHM to the target object. providing, by a user, a precision level that represents a level of precision required for the DHM to perform a task associated with the target object; obtaining information associated with the original DHM posture, the obtained DHM posture information including a position of a head of the DHM; obtaining information associated with the target object, the obtained target object information including a size of the target object and an orientation of the target obj ect; obtaining a distance from the head of the DHM to the target object; generating a measure of vision of the DHM of the target object that the DHM is visually targeting, based on one or more parameters which include the obtained DHM posture information, the obtained target object information, and the obtained head-target distance; based on the measure of vision and on the precision level, generating a constraint of vision of the DHM to the target object, the constraint of vision representing an ability of the DHM to perform a task associated with the target object; based on the vision constraint, generating an updated DHM posture; and using the updated DHM posture to evaluate a risk of injury of a human and to properly size an environment around humans of different anthropometries; wherein the updated DHM posture provides an increased ability of the DHM to perform the task associated with the target object as compared with an ability of the DHM to perform the task associated with the target object using the original DHM posture, wherein the updated DHM posture is further generated based on an inverse kinematics engine and degrees of freedom of the DHM, and the inverse kinematic engine receives the vision constraint and determines the degrees of freedom of the DHM; wherein the vision constraint further represents a measure of closeness of the DHM to the target object, and the updated DHM posture is further generated based on the measure of closeness of the DHM to the target object.