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Photo camera shutter vs film camera shutter (rotary shutter)
The motion blur settings in Maxwell can be set both for a photo camera and a film camera, so it's important to know how the shutter works in each case to understand the settings.
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The shutter on a film camera however is a rotating disc with an opening cut into it, called a rotary shutter, and the angle of this opening determines how long the film is exposed to light as the film rolls by the shutter. Setting the camera this way means the motion blur effect still depends on the fps of your animation because a frame of film can't be exposed longer than the fps setting of the animation, even if the rotary shutter is open during the whole frame. This means an animation running at 60fps will have less of a motion blur effect than one running at the typical 24fps for film.
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h6. The angle of the cut in the rotary shutter determines how long the film is exposed to light. In this case the angle is 180º
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In the Maxwell camera settings you can pick "Use rotary shutter" and set the shutter angle, by default 180º. Setting the angle smaller means the film will be exposed to light for a shorter time - less motion blur. You can set it all the way to 360º which means effectively there is no shutter blocking the light and the motion blur will be based purely on the frames per second setting of your animation.
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If you wish to mimic the typical long exposures you can get with a photo camera, even several seconds long, you should use the shutter speed and set it accordingly - 1/1 for one second, 1/0.5 for 2 seconds, 1/0.25 for 4 seconds etc. |
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This parameter in Render Options controls how many times Maxwell should sample the motion of the animation, given a certain exposure time set by the camera parameters. If your exposure time is long and your object doesn't move in a straight line during that time, you should set the steps high enough to smoothly capture the different positions of the object moving. You should also set the steps high enough if you have fast rotating objects, like a propeller, which can rotate several hundred degrees even between two frames. Maxwell will take the number of samples between those two frames (called sub frame samples) that you set in the step setting.
In general term, if the motion path you are getting in the render is different to the expected, this may be caused by an insufficient number of substeps. Increasing them on the scene export may provide a more accurate motion path.
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