Image generating device, image generating method, and non-transitory information storage medium

1. A computer-readable non-transitory information storage medium having stored thereon a program for controlling a computer to execute the processing of:

changing a mass or a gravitational acceleration of each of a plurality of rigid bodies which are constrained to one another and included in a first object based on an angle between each of the plurality of rigid bodies and a second object;

physically calculating a motion of each of the plurality of rigid bodies included in the first object based on the changed parameter; and

rendering an image representing a surface of the first object based on the motions of the plurality of rigid bodies included in the first object.

2. The computer-readable non-transitory information storage medium having stored thereon a program according to claim 1 , wherein the processing of changing the mass or the gravitational acceleration comprises selecting at least one rigid body out of the plurality of rigid bodies which are constrained to one another and included in the first object based on the angle between each of the plurality of rigid bodies and the second object, and changing the mass or the gravitational acceleration of the selected rigid body.

3. The computer-readable non-transitory information storage medium having stored thereon a program according to claim 2 , wherein the processing of changing the mass or the gravitational acceleration comprises selecting at least one rigid body out of the plurality of rigid bodies included in the first object based on proximity between each of the plurality of rigid bodies included in the first object and a contact position at which the second object is in contact with a mesh representing a surface of the first object.

4. The computer-readable non-transitory information storage medium having stored thereon a program according to claim 3 , wherein the processing of changing the parameter relating to the gravity comprises changing the parameter so that a value of the mass or the gravitational acceleration of the selected rigid body changes based on proximity between the selected object and a contact position between the first object and the second object.

5. The computer-readable non-transitory information storage medium having stored thereon a program according to claim 3 , wherein the processing of changing the mass or the gravitational acceleration comprises selecting at least one of the plurality of the rigid bodies included in a range which is represented by a prolate spheroid wherein a center of the prolate spheroid is the contact position and which stretches in a predetermined direction.

6. The computer-readable non-transitory information storage medium having stored thereon a program according to claim 3 , wherein the processing of changing the mass or the gravitational acceleration comprises selecting at least one rigid body so that an angle formed by a vector from a position of the selected rigid body to the contact position and a vector from a position of a rigid body connected to the selected rigid body to the position of the selected rigid body satisfies a predetermined condition.

7. The computer-readable non-transitory information storage medium having stored thereon a program according to claim 3 wherein the processing of physically calculating the motion of the rigid body comprises calculating a motion of the second object based on an angle between the mesh and the second object.

8. The computer-readable non-transitory information storage medium having stored thereon a program according to claim 2 , wherein the processing of changing the parameter relating to the gravity comprises changing the parameter so that a value of the mass or the gravitational acceleration of the selected rigid body changes based on the angle between the rigid body and the second object.

9. The computer-readable non-transitory information storage medium having stored thereon a program according to claim 1 , wherein the processing of changing the mass or the gravitational acceleration comprises changing a change amount of the parameter based on whether or not the value of the parameter increases from mass in a previous frame.

10. An image generating device, comprising:

gravity parameter changing means for changing a mass or a gravitational acceleration of each of a plurality of rigid bodies which are constrained to one another and included in a first object based on an angle between each of the plurality of rigid bodies and a second object;

physical calculation means for physically calculating a motion of each of the plurality of rigid bodies included in the first object based on the changed parameter; and

image rendering means for rendering an image representing a surface of the first object based on the motions of the plurality of rigid bodies included in the first object.

11. An image generating method, comprising:

changing a mass or a gravitational acceleration of each of a plurality of rigid bodies which are constrained to one another and included in a first object based on an angle between each of the plurality of rigid bodies and a second object;

physically calculating a motion of each of the plurality of rigid bodies included in the first object based on the changed parameter; and

rendering an image representing a surface of the first object based on the motions of the plurality of rigid bodies included in the first object.