Fusion Page: Key Frames use floating point numbers?

I opened up the table view for Key Frames in the Fusion page and noticed the numbers were 17.0, 105.0 and 208.0. Really? I can have a Key Frame change occur in part of a frame? When I tried to enter 17.5, the number reverted to an integer.

Then I notice the labels under the time line were also floating point numbers. Is there a reason for the frames being in floating point numbers?

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Technically frame numbers in comp almost always have to be handled as float or double "for reasons", because there are multiple situations where time samples have to be non-integer. Transform motion blur for example, where transform time samples are taken around current frame time and as such all parameter curves have to be evaluated at those fractional times too. Even with float precision comp can run into issues if frame numbers are high (mapping from timecode to frame number can produce these easily), motion blur samples won't have enough granularity anymore and produce stair-stepped look.

I think this is more of an UI issue because if user can't set frames to be fractional values, they shouldn't be presented as such either.

I opened up the table view for Key Frames in the Fusion page and noticed the numbers were 17.0, 105.0 and 208.0. Really? I can have a Key Frame change occur in part of a frame? When I tried to enter 17.5, the number reverted to an integer.

Then I notice the labels under the time line were also floating point numbers. Is there a reason for the frames being in floating point numbers?

The attachment DaVinciResolve.png is no longer available

Right mouse click on the play controls and you will see a menu with how many frames or half frames to to move with arrow keys. Choose 0.5 and use arrow keys to move half a frame, or subframe. This can be useful for rotoscoping or some effects where you need that kind of precision. Maybe compositing gunshot wounds or muzzle flashes etc. Or manual roto adjustments of very fast objects. Or if you want to skip ahead, say 10 frames at the time.

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I don't know if you have to use float numbers for your footage for this to work or not, or some setting in the preferences, but for me it works.

Manual says this:

Frame Increment Options

Right-clicking either the Play Reverse or Play Forward buttons opens a contextual menu. This menu contains options to set a frame increment value, which lets you use a keyboard shortcut to move the playhead in sub-frame or multi-frame increments.

Moving the playhead in multi-frame increments can be useful when rotoscoping. Moving the playhead in sub-frame increments can be useful when rotoscoping or inspecting interlaced frames one field at a time (0.5 of a frame).

0.5 is only useful for interlaced footage, for anything else 2D it makes little sense as there is no frame to view at that half-increment anyway without doing some kind of frame interpolation which it doesn't do. In 3D scene view it might have some usefulness as it does show the scene at that fractional time moment.