I'm no expert in professional-grade motion blur, but the FilmStrip library for Flash has let me toy around with it a little. I noticed that when both a scene's subjects and its camera are animated, the motion of the camera can impact blurs in sometimes unwanted ways. For example, an object might be moving very fast in one direction, but then if the camera swivels in the opposite direction it can actually reverse the blur of the subject.

As I've described in earlier posts, FilmStrip generates motion blur by generating a series of subframe captures within the real animation flow. If the camera is also animating, this will affect the perspective of the subframes as well as the primary frame. Since allowing the camera to animate normally turned up some unnatural-looking results (like the swivel example I mentioned), the next thing I tried was to entirely cut out camera animation. This had the effect of completely restoring the blurs of the animation subjects, but it also didn't really look natural to the eye. I suppose we've all grown up watching the particular way TV and film cameras capture things that it's pretty ingrained, things either read as fake or natural even if we don't know the exact reasons.

So next I tried an in-between: allowing the camera to animate during subframe captures, but just not as much as it normally would, which looked a lot better. I achieved this by applying a multiplier to the camera animation. By dampening camera motion during subframe animation, but not cutting it entirely, camera motion can still have some interplay without fully overpowering the blur of the subjects.

I've added a property to the MotionBlurSettings class called cameraBlurPercent, which now defaults to CAMERA_BLUR_NATURAL (0.5), cutting the influence of camera motion in half. Two other constants added to the class, CAMERA_BLUR_NONE (0), CAMERA_BLUR_ABSOLUTE (1) allow you to toggle camera influence based on your particular animation. You can also fine-tune it to another percentage such as 0.25, or do crazy experiments by setting it above 1 to magnify camera motion.

Once again here's my little x-wing clip which I think shows a really natural interplay of camera motion and subject motion. (This MP4 doesn't seem to work in Chrome for Mac, try it in Safari instead.)

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