Hello Guys - especially those from Adobe!
There is a strange (buggy or new) behavior with Illustrator graphics and motionblur:
When I import an AI-graphic as composition and toggle collapse transformation and motionblur switches on both, AI graphic and comp, the graphic stays blured after the motion stopped. This is not happening when I deactivate collapse transformation on one of those items.
Now to the crazy part: if collapse transformation is activated on both items, motion blur stays at and after the last frame. When I go one frame further and change the scaling (99% or 101%) of the comp, motion blur disappears as it should be.
Playing around with scaling from very small to very large seems to resolve this behavior. But it comes back randomly.
Can someone confirm this?
Cheers,
Martin
11
Replies
There is no bug if you are seeing motion blur on the same frame as the last keyframe because that frame is still playing back. The relationship between motion blur and the timing of the frame is set in the Advanced composition settings Advanced tab. The default is a 180º shutter and -90 for the phase. If you zoom in on the timeline to the frame level you can see width and position of the shutter. in this first screenshot the shutter angle is set at the maximum value of 720º so the motion blur covers two full frames and the phase is -211º so the shutter never lines up with the frames precisely. The lighter colored bar is the period of time where the shutter is open.
In this screenshot the shutter is set to the default value of 180º and the phase is at the default value of -90º. This closely imitates the motion blur you get with a motion picture camera. Notice how the light vertical bar is half the width of a frame:
The number of samples determines the look of the motion blur, the shutter angle determines how much movement is blurred and the phase determines when the blur happens in relationship to the movement. You'll have to study up on how a motion picture camera shutter works to get your head wrapped around this.
Move one frame forward from the last keyframe in the timeline and the motion blur will be gone. Move one frame back and the motion blur will be twice as large.
If you get occasional random blur frames in your preview then it is most likely a cache problem. If you really want to have the motion blur stop at last keyframe you can adjust the phase but you should also realize that if you do the layer will still be moving in that last frame so you'll have one frame without motion blur when there is movement.
I hope this helps. It is important for you to understand how motion picture camera shutters work and how that relates to electronic shutters on video cameras if you are going to accurately match the motion blur in your composite to the motion blur in your original video.
I took a look at your project files and I have a couple of questions. First why is the .ai file nested in it's own pre-comp and why is the file not in the center of the comp:
One more question, why is the comp set to Ray Traced rendering?
I probably should have asked that question first.
The first thing I did with the Square comp was to press the U key twice to check for modified properties. The anchor point and position error were the first thing I noticed in the CC2017 version of the project. Rest the transform properties and the motion blur behaves as expected. I don't know why this fixes it but it does. You should always be using Snap to Pixel in Illustrator when you create artwork for video and life is a lot easier if you make sure that your shapes are an even number of pixels high and wide. Your square is 191 X 191.
I also discovered that if you click on the quality and sampling box in Comp 1 two or three times the problem goes away. There is definitely a strange bug here, but it can be fixed by fixing the positioning in the Square comp.
I also tried importing the .AI file as a comp and found that the position was offset agin by .3 pixels. This tells me that this is where the problem lies. If you just import the .ai file as footage, or you replace the Square footage with the .ai file and turn on motion blur that the problem goes away.
I then opened the CC2015.3 project in CC2017 and found that the position error was still there but I could not reproduce the hanging motion blur. The file worked perfectly. I also did not get a warning that Ray-traced rendering was chosen and
So, yes, there is a bug somewhere and I'm pretty sure that it has something to do with importing the .ai file as a composition when the dimensions are not an even number and are not lined up with the pixel grid. If you select the .ai file and choose create new comp from selection then you replace Square in Komp 1 with Square 2 the problem also goes away.
That's the long answer. You should file a bug. The short answer, use good standards and practices when you create artwork in Illustrator, or Photoshop for that matter, and make sure that your elements are lined up with the pixel grid.
https://forums.adobe.com/people/Rick+Gerard wrote
One more question, why is the comp set to Ray Traced rendering?
I probably should have asked that question first.
Side note: that notification is not about the ray-traced renderer. That is about GPU-accelerated effects. You are getting that notice in CC 2017, but not the earlier one because some of the GPU acceleration stuff is new in CC 2017. I don't recall any earlier versions having that notice.
You are getting it in this case because the OP has an NVIDIA card (using CUDA) and you have an AMD card (using OpenCL).
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