Segement Title: Critique 02 on the Motion Blur Effect from The Prince of TennisPlot SummaryPrince of Tennis is a movie about a highly skilled middle school tennis player in a new school, new tennis club, and new competition. The movie makes plenty of use of CG effects to exaggerate a lot of the physics in the movie.The EffectIn one scene, one of the characters is practicing by using a machine that launches a multitude of tennis balls at him simultaneously. The character swings and hits all the tennis balls back. The tennis balls are shown in slow motion in the video as the character swings at normal speed to hit them all. The motion blur is applied on the character to exaggerate his speed further.
   Physical reason of Motion Blur:When a camera creates an image, that image does not represent a single instant of time. Because of technological constraints or artistic requirements, the image represents the scene over a period of time. As objects in a scene move, an image of that scene must represent an integration of all positions of those objects, as well as the camera's viewpoint, over the period of exposure determined by the shutter speed.Usage of Motion Blur:In the plots we describe above, motion blur is usually used to express or exaggerate the speed of motion.It can also be used to show the effect of traversing over the time. How We Think it Was DoneWe think the cheapest way to achieve motion blur effect is to follow/simulate the physical reason of motion blur:Given a series of sharp frames, for each frame, we overlay(weighted average) its neighbor frames and substitue the original frames. We can have three different choices: For Frame(i) Past motion blur: We use the weighted average of Frame(i), Frame(i-1), Frame(i-2), Frame (i-3), Frame(i-4)... (T frames in total) Future motion blur: We use the weighted average of Frame(i), Frame(i+1), Frame(i+2), Frame (i+3), Frame(i+4)... (T frames in total) Past and Future motion blur: We use the weighted average of ...Frame(i-2),Frame(i-1), Frame(i), Frame(i+1), Frame(i+2)... (T frames in total) Two parameters can be adjusted: 1. Number of frames: T. The larger this number is, the more frames will be overlaid, thus the longer the tail will be. 2. Weights: We can choose to put more weights on the frames near Frame(i) and put less weights on the frames far from Frame(i), so that the original frames will still be dominant. Something to notice: In the end of the motion blur, if we want the blured motion to converge to a sharp ending, we have to do the following: If Frame(i) is already the the last frame, Frame(i+1)=Frame(i+2)=Frame(i+3)...=Frame(i). For the clip of Prince of Tennis, we believe they use the past motion blur. The stick in actors' hand has highlight in some position and is dim in others positions. This is introduced by lighting effect. CG balls are added afterwards. Alternate Ways of Doing the EffectWe did a survey about motion blur techniques used in static images and videos
How This Applies to Our ProjectWe're going to achieve a similar effect in The Prince of Tennis - Our player hits multiple balls back in a high speed with motion blur effect around his movement.
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