1. A method of creating motion blur in a computer generated image, the method comprising: receiving a first blur parameter value associated with a first animation variable; determining a first evaluation time of the first animation variable based on the first blur parameter value; determining a first animation variable value based on the first evaluation time; determining a first modification of an object in a scene based on the first animation variable value; receiving a second blur parameter value associated with a second animation variable; determining a second evaluation time of the second animation variable based on the second blur parameter value; determining a second animation variable value based on the second evaluation time; determining a second modification of the object in the scene based on the second animation variable value; applying the first and second modifications to the object using a computer processor to create a modified object, wherein the object includes at least one control point, and applying the first and second modifications comprises: a) evaluating at least a first function using the first animation variable value to determine a first control point component, wherein the first control point component is based on the first evaluation time; b) evaluating at least a second function using the second animation variable value to determine a second control point component, wherein the second control point component is based on the second evaluation time; and c) combining the first and second control point components to determine a position of the control point based on at least the first and second evaluation times by: 1) weighting the first control point component according to a first weight associated with at least the first animation variable; 2) weighting the second control point component according to a second weight associated with at least the second animation variable; and 3) combining the weighted first and second control point components to determine the position of the control point; and rendering the modified object including the first and second modifications to create at least a portion of a computer-generated image including the object.