Method of creating image frames, storage medium and apparatus for executing program

A storage medium for storing a program read and executed by a program executing apparatus, said program allowing said program executing apparatus to create image frames forming a dynamic image obtained by projecting a virtual three-dimensional object which is moving with predetermined motion characteristics in a virtual three-dimensional world coordinate space, and allowing the program executing apparatus to execute:

• a three-dimensional world coordinate calculating step which calculates a three-dimensional position of the three-dimensional object in the three-dimensional world coordinate space according to the motion characteristics;
• a two-dimensional coordinate calculating step which calculates a two-dimensional position on a virtual camera screen corresponding to the calculated three-dimensional position;
• a history accumulating step which accumulates a history of the two-dimensional position calculated by said two-dimensional coordinate calculating step;
• an object drawing step which draws an image representing the three-dimensional object at the two-dimensional position calculated by said two-dimensional coordinate calculating step;
• and
• a locus drawing step which draws a line segment or a shape so as to connect a plurality of positions including the two-dimensional position calculated by said two-dimensional coordinate calculating step and at least one position accumulated by said history accumulating step when at least one image frame was generated, in order of those positions starting from the position calculated earlier.

A program read and executed by a program executing apparatus, said program allowing said program executing apparatus to create image frames forming a dynamic image obtained by projecting a virtual three-dimensional object which is moving with predetermined motion characteristics in a virtual three-dimensional world coordinate space, and allowing said program executing apparatus to execute:

• a three-dimensional world coordinate calculating step which calculates a three-dimensional position of the three-dimensional object in the three-dimensional world coordinate space according to the motion characteristics;
• a two-dimensional coordinate calculating step which calculates a two-dimensional position on a virtual camera screen corresponding to the calculated three-dimensional position;
• a history accumulating step which accumulates a history of the two-dimensional position calculated by said two-dimensional coordinate calculating step;
• an object drawing step which draws an image representing the three-dimensional object at the two-dimensional position calculated by said two-dimensional coordinate calculating step;
• and
• a locus drawing step which draws a line segment or a shape so as to connect a plurality of positions including the two-dimensional position calculated by said two-dimensional coordinate calculating step and at least one position accumulated by said history accumulating step when at least one image frame was generated, in order of those positions starting from the position calculated earlier.

A program executing apparatus for executing a program for displaying a dynamic image comprising image frames whose contents change in accordance with operations of a user, said dynamic image being obtained by projecting a virtual three-dimensional object moving with predetermined motion characteristics in a virtual three-dimensional world coordinate space, said program executing apparatus comprising:

• three-dimensional world coordinate calculating means which calculates a three-dimensional position of the three-dimensional object in the three-dimensional world coordinate space according to the motion characteristics;
• two-dimensional coordinate calculating means which calculates a two-dimensional position on a virtual camera screen corresponding to the calculated three-dimensional position;
• history accumulating means which accumulates a history of the two-dimensional position calculated by said two-dimensional coordinate calculating means;
• object drawing means which draws an image representing said three-dimensional object in the two-dimensional position calculated by said two-dimensional coordinate calculating means;
• and
• locus drawing means which draws a line segment or a shape so as to connect a plurality of positions including the two-dimensional position calculated by said two-dimensional coordinate calculating means and at least one position accumulated by said history accumulating means when at least one image frame was generated, in order of those positions starting from the position calculated earlier.