Tooltips wrong for Image sequence Node in Compositor (and likely other image sequene inputs)
Closed, InvalidPublic

Description

System Information
Linux, Nvidia GFX, Intel CPU
Blender Version
Broken: Probably all versions
Worked: _
Short description of error

  • Tooltips for Frames, Start Frame, Offset give wrong information (and the options are already really confusing)
  • Many (Most?) Blender users randomly fiddle with these until they do what they want.
  • I'm still not sure what the options mean, and I'm not sure anyone else does :P

Exact steps for others to reproduce the error
What I'm trying to do:
I have Scene starting at frame 101 and ending at frame 300
I have an Image Sequence on disk starting at frame frame_0001.png and ending at frame frame_0300.png
I want to only use 200 frames, matching the scene numbers: frame_0101.png to frame_0300.png.

Steps:
This will probably be similar for lower numbers.
1- Start with 300 frames of images on disk, with _0001 to _0300 as frame numbers.
2- have a blend file starting at frame 101 and ending at frame 300
3- goal is to load the frames from disk that correspond with the frame numbers of the scene (-0101 to -0300), Shift A, Input, Image, click open, and select all your images and press enter.

4- Frames Tooltip "Number of Images of a Movie to Use":
4a- it's not a movie (should be image sequence)
4b- I input 200 because I'm only going to use the last 200 frames.
5- Start Frame Tooltip "Global Starting Frame of the Movie/Sequence, assuming first picture has #1"
5b- this seems to really mean "Blender Scene Frame # to start playback" I set it to 101, my start frame for the scene.
6- Offset: Toolip "Offset the number of the frame to use in this animation":
6a- The tooltip doesn't actually give any extra information. Since I have frames on disk, and scene frames, it doesn't say which is being offset, nor does it say if it's offseting the number or from the actual start frame on disk or scene, mathematically:
result = offset + a, to make it clear what happens, I need to know what 'a' is - I already know it's a frame in an animation, so the tooltip doesn't actually tell me.
6b- according to Ton It's the frame number that gets loaded. Tests reveal that it is the frame number - 1 (i.e. if I want to start at frame 1, input 0 , etc.) So I put in frame 100

Result:
1- the sequence starts playing back fine, starting from scene.frame = 101, pulling image frame_0101.png from disk (success!!!!!)
2- the sequence stops playing at frame 200 instead of frame 300!!!! this is because Frames isn't the number of frames of the movie to *use*, rather it is the number of frames of the movie on *disk*. I have two options:
2b- change frames to 300, then my comp will get 200 frames as desired.
2c- delete the first 100 frames (frame_0001.png to frame_0101.png) from disk.

Details

Type
Bug
bassam kurdali (bassamk) updated the task description. (Show Details)
bassam kurdali (bassamk) raised the priority of this task from to Needs Triage.
bassam kurdali (bassamk) set Type to Bug.

Fixing the tooltips would help a lot but IMO the following is functionally correct and matches how most editors work:

1- you have a number of frames on disk. That's an input.
2- In blender you specify the following extra inputs:
a- In Point: This is a frame offset from the first frame on disk.
b- Out Point: This is a frame offset from the first frame on disk.
c- Blender Start Frame: this is the Scene frame at which the playback starts.

Otherwise I propose the following tooltips:
Frames: "Number of frames of the Movie/Sequence to Use, Starting from the first Frame on disk"
Start Frame: "Blender Scene Frame to start Playback"
Offset: "Offset from Frame 1 on disk, regardless of whether this frame exists or not...." (suggestions welcome)

btw, on reflection, we're awefully close to in point / out point as is:

Frames = Out Point - measured from first frame physically on disk
Offset = In point measured from frame # 1 (regardless if it is on disk or not)
Start Frame = Start Frame: blender frame at which to start playback of the clip.

So you could keep Frames and just rename to Out Point
create an In Point property that is consistent (measures from start frame on disk, there's nothing magical about the number 1)
Keep Start Frame as is (but fix the tooltip)

What would be absolutely amazing is if once you selected Image Sequence or Movie, the node gave you a little visual timeline to adjust the in/out, placement, and length of the clip.

https://www.dropbox.com/s/u5nfbms8asltbsn/timeline_node.jpg?dl=0

Bastien Montagne (mont29) claimed this task.

This is not a bug report, this is a mix of feature request, user assistance request, Tip/ui message ranting, and design task. That kind of stuff is for ML and/or IRC, we have already too much non-bugs tasks in this tracker, please do not add to the noise!

In your case you just set 'frames' to 300, and the rest leave as default and it works fine. Or to be clear, for the image sequence you set:

  • start frame: 1
  • total: 300
  • offset: 0

I am not defending that this is an awesome system. It's literally just the variables in a few lines of code you can set. But it works.
This system was not designed for usability or docs. We needed something quick to work. In 1995! The proper solution would be a nice UI to define sequences with nice viz - maybe like colorband or so (mini sequencer).

The tooltip wording can be fixed. The plus one or minus one thing I wouldn't worry about. If you can mentally work with "first frame is number 1" (and not zero) you are used to such issues.

hehe, yes, it definitely feels like a quick solution that 'works' but not something defined - and it does work in the sense that you can for sure input numbers that do the right thing.

I think getting tooltips right would at least make it more discoverable how it works - the "I change numbers randomly until it does what I want" is pretty common, would be nice to give people a hand.

The reason I didn't do what you suggested (it's valid!) is because the first 100 frames weren't really needed, deleting them was more reasonable in my case.

My suggestions for tootlips, for discussion:

Frames: "Number of frames in sequence to consider, beginning from first frame on disk"
Start Frame: "Blender Scene Frame number to begin playback of sequence"
Offset: "Sequence frame number to begin playback, offset from frame #1"

Is this clear? what do others think?
I can also make a proposal somewhere for a easier way to do this as a future UI task.