In an information processing apparatus, an external-information acquisition unit acquires external information such as an image, a sound, textual information, and numerical information from an input apparatus. A field-image generation unit generates, as an image, a “field” that acts on a particle for a predetermined time step based on the external information. An intermediate-image memory unit stores an intermediate image that is generated in the process of generating a field image by the field-image generation unit. A field-image memory unit stores the field image generated by the field-image generation unit. A particle-image generation unit generates data of a particle image to be output finally by using the field image stored in the field-image memory unit.