Assessment Criteria for 2D Shape Transformations in Animation

The assessment of 2 0 shape transformations (or morphing) for animation is a dificult task because it is a multi-dimensional problem. Existing morphing techniques pay most attention to shape information, interactive control and mathematical simplicity. This paper shows that it is not enough to use shape information only and we should consider other factors such as structure, dynamics, timing etc. The paper also shows that an overall objective assessment of morphing is impossible because factors such as timing are related to subjective judgement, yet local objective assessment criteria, e.g. based on shape, are available. W e propose using “area preservation” as the shape criterion for the ZD case as an acceptable approximation to iivolume preservation” in reality, and use it to establish cases in which a number of existing techniques give clearly incorrect results. The possibility of deriving objective assessment criteria fo r dynamics simulations and timing ,under certain conditions is discussed in the paper.