Transfer of motion between animated characters
Motion may be transferred between portions of two characters if those portions have a minimum topological similarity. The elements of the topology that are similar are referred to as basic elements. To transfer motion between the source and target characters, the motion associated with the basic elements of the source character is determined. This motion is retargetted to the basic elements of the target character. The retargetted motion is then attached to the basic elements of the target character. As a result, the animation of the basic elements in the topology of the target character effectively animates the target character with motion that is similar to that of the source character.
1. A computer-implemented method for transferring motion from a source character having a source topology to a target character having a target topology, comprising:
receiving a user input that identifies basic elements in the source topology and basic elements in the target topology, wherein the source topology is arbitrarily different than the target topology, the basic elements in the source topology comprise a subset of elements in the source topology, the basic elements in the target topology comprise a subset of elements in the target topology, and the basic elements in the source topology are homotopic with the basic elements in the target topology;
computing a source-to-canonical transformation between a frame of reference of the source topology and a frame of reference of a canonical topology, wherein the frame of reference of the source topology and the frame of reference of the canonical topology are different;
retargetting motion from the basic elements of the source topology to the canonical topology using the source-to-canonical transformation to produce a normalized representation of the motion of the basic elements of the source topology;
computing a target-to-canonical transformation between a frame of reference of the target topology and the frame of reference of the canonical topology, wherein the frame of reference of the target topology and the frame of reference of the canonical topology are different;
retargeting the normalized representation of the motion of the basic elements of the source topology to the target topology using the target-to-canonical transformation to produce retargeted motion of the basic elements of the target topology;
storing in a memory a representation of the target topology with the attached retargeted motion of the basic elements of the target topology; and
storing in the memory the normalized representation of the motion and the canonical topology in a database of motion for reuse with different target characters.
2. The computer-implemented method of claim 1 , further comprising storing the source-to-canonical transformation with the source character.
3. The computer-implemented method of claim 1 , further comprising storing the target-to-canonical transformation with the target character.
4. The computer-implemented method of claim 1 , wherein the source topology and the canonical topology are placed in the same pose to compute the source-to-canonical transformation.
5. The computer-implemented method of claim 1 , wherein the target topology and the canonical topology are placed in the same pose to compute the target-to-canonical transformation.
6. The computer-implemented method of claim 1 , further comprising:
computing a source-to-target transformation between a frame of reference of the source topology and the frame of reference of the target topology when the source topology and the target topology are placed in the same pose; and
retargetting motion from the basic elements of the source topology to the target topology using the source-to-target transformation to produce the retargeted motion of the basic elements of the target topology.
7. A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause a computer system to transfer motion from a source character having a source topology to a target character having a target topology, by performing the steps of:
receiving user inputs identifying basic elements in the source topology and basic elements in the target topology that correspond to the basic elements in the source topology, wherein the source topology is arbitrarily different than the target topology, the basic elements in the source topology comprise a subset of elements in the source topology, the basic elements in the target topology comprise a subset of elements in the target topology, and the basic elements in the source topology are homotopic with the basic elements in the target topology;
retargetting motion from the basic elements of the source topology to the canonical topology using the source-to-canonical transformation to produce a normalized representation of the motion of the basic elements of the source topology;
computing a source-to-canonical transformation between a frame of reference of the source topology and a frame of reference of a canonical topology, wherein the frame of reference of the source topology and the frame of reference of the canonical topology are different;
computing a target-to-canonical transformation between a frame of reference of the target topology and the frame of reference of the canonical topology, wherein the frame of reference of the target topology and the frame of reference of the canonical topology are different;
retargeting the normalized representation of the motion of the basic elements of the source topology to the target topology using the target-to-canonical transformation to produce retargeted motion of the basic elements of the target topology;
storing in a memory a representation of the target topology with the attached retargeted motion of the basic elements of the target topology; and
storing in the memory the normalized representation of the motion and the canonical topology in a database of motion for reuse with different target characters.
8. The computer-readable storage medium of claim 7 , further comprising storing the storing the source-to-canonical transformation with the source character.
9. The computer-readable storage medium of claim 7 , further comprising storing the storing the target-to-canonical transformation with the target character.
10. The computer-readable storage medium of claim 7 , wherein the source topology and the canonical topology are placed in the same pose to compute the source-to-canonical transformation.
11. The computer-readable storage medium of claim 7 , wherein the target topology and the canonical topology are placed in the same pose to compute the target-to-canonical transformation.
12. The computer-readable storage medium of claim 7 , further comprising:
computing a source-to-target transformation between a frame of reference of the source topology and the frame of reference of the target topology when the source topology and the target topology are placed in the same pose; and
retargetting motion from the basic elements of the source topology to the target topology using the source-to-target transformation to produce the retargeted motion of the basic elements of the target topology.
13. A computer system for transferring motion from a source character having a source topology to a target character having a target topology, comprising:
a processor; and
a memory storing instructions that when executed by the processor are configured to cause the computer system to:
receive user inputs identifying basic elements in the source topology and basic elements in the target topology that correspond to the basic elements in the source topology, wherein the source topology is arbitrarily different than the target topology, the basic elements in the source topology comprise a subset of elements in the source topology, the basic elements in the target topology comprise a subset of elements in the target topology, and the basic elements in the source topology are homotopic with the basic elements in the target topology;
retarget motion from the basic elements of the source topology to the canonical topology using the source-to-canonical transformation to produce a normalized representation of the motion of the basic elements of the source topology,
compute a source-to-canonical transformation between a frame of reference of the source topology and a frame of reference of a canonical topology, wherein the frame of reference of the source topology and the frame of reference of the canonical topology are different;
compute a target-to-canonical transformation between a frame of reference of the target topology and the frame of reference of the canonical topology, wherein the frame of reference of the target topology and the frame of reference of the canonical topology are different;
retarget the normalized representation of the motion of the basic elements of the source topology to the target topology using the target-to-canonical transformation to produce retargeted motion of the basic elements of the target topology;
store in the memory a representation of the target topology with the attached retargeted motion of the basic elements of the target topology; and
store in the memory the normalized representation of the motion and the canonical topology in a database of motion for reuse with different target characters.
14. The computer system of claim 13 , wherein the source-to-canonical transformation is stored with the source character.
15. The computer system of claim 13 , wherein the target-to-canonical transformation is stored with the target character.
16. The computer system of claim 13 , wherein the source topology and the canonical topology are placed in the same pose to compute the source-to-canonical transformation.
17. The computer system of claim 13 , wherein the target topology and the canonical topology are placed in the same pose to compute the target-to-canonical transformation.
18. The computer system of claim 13 , wherein the instructions that when executed by the processor are further configured to cause the computer system to:
compute a source-to-target transformation between a frame of reference of the source topology and the frame of reference of the target topology when the source topology and the target topology are placed in the same pose; and
retarget motion from the basic elements of the source topology to the target topology using the source-to-target transformation to produce the retargeted motion of the basic elements of the target topology.