1. A system, comprising: a processor; and a computer-readable medium comprising instructions that, when executed by the processor, cause the processor to perform operations, for planning a grasping-device approach to an object by a grasping device, a pre-grasp device position, and a pre-grasp device pose, comprising: obtaining input data including grasping-device data, object data, and environmental-constraint data; determining, based on at least the grasping-device data, a grasp volume model; determining a test approach vector; determining, using the test approach vector, the environmental-constraint data, and the grasp volume model, whether modification to the test approach vector is needed; modifying, if it is determined that the modification is needed, the test approach, yielding a resulting approach vector; determining, if it is determined that the modification is not needed, that the test approach is the resulting approach vector; determining virtual floor data indicating a position below which the grasping device cannot move; and determining, based on the resulting approach vector, the virtual floor data, the grasp volume model, and the object data, the grasping-device approach, the pre-grasp device position, and the pre-grasp device pose.