2.82 - image sequence nodes not playing during render


Why does an animation with 500 frames in 2 image sequence nodes render as a video that only shows 1 frame?

Can anyone point out the mistake I made with trying to render an animation with this setup? (image below)

Can someone tell me what the image sequence settings do, precisely? And how to use them properly?

Is there a way to put PNG background and the EXR foreground into the VSE and still do compositing on the video?


(Or, is compositor in 2.82 working correctly with image sequences? I didn’t find any documentation for the node… anyway:)

Trying to render to MP4 from a composited image sequence only renders 1 frame for the entire duration of the video. I assume this is due to image sequence nodes not changing their values during rendering.

Please look at the image at this link:

I have 575 EXR files and About 2000 png frames from the movie.
Regardless of whether I load all PNG files or only 575 the image sequence node shows ~2000 frames. The first frame shows in teh thumbnail, but changing any values closes the previews.
Can someone explain what the correct values for the image sequences would be with those numbers?

The Video Editor track is empty at this point. I had the original video that you can see top-left but I removed it because I wanted to use the rendered pngs. Also, I didn’t know how to use the compositor overlay in the VSE.

The node with the green marking around its Offset setting is the rendered EXR sequence. I turned the offset to #frame because I thought that might have been the problem. However, it didn’t work.
Cyclic was turned off for all sequences when I was rendering.

You can see that there is no thumbnail, and the backdrop turned pink. I have looked on youtube and searched around the web but no luck with finding any description of how the node is supposed to be used.

It’s impossible to diagnose your issue without knowing:

  1. how you’ve already numbered the existing image sequences
  2. at what frame, globally, in your current scene you expect the sequences to begin

But I can assure you that none of the node values need to be driven or animated. FYI if an image datablock is designated as a sequence, it will automatically find all the numbered frames in the given directory regardless of what initial file range you have selected in the file browser.

how you’ve already numbered the existing image sequences

So I take it the frames need to be numbered (i. e. files on disk named) in a specific way for the ISq node to use them?
The EXR are numbered in two ways - one group is a 4-digit, while the other is a 5-digit frame “number.” I say two groups because they seem to have been made at two separate occasions (2 days apart). I was not aware of that.
The PNG files were numbered differently; they still had 3-slot sequential numbers in the end but the start of the file name was a keyword.

at what frame, globally, in your current scene you expect the sequences to begin

Another great point - I don’t even know what globally means in this sense. Does it reference the entire loaded sequence of images and a location from within that sequence that will be the starting point, or the location in the Blender timeline window and at which point after frame 0 the ISq will start animating? Or something completely different?

This is what I meant with documentation.

Yes. It’s pretty flexible as long as the prefix or the numbering convention doesn’t change in the middle of the sequence. If a frame sequence has a break in the numbering convention, like going from 4 digits to 5 digits, that could cause problems.

Assuming you have consistent numbering though, the other potential variable is what the number of the first filename is. Does it start at 0001.exr? Does your blender scene (that’s what I mean by global) also start at frame 1? Do you want these numbers to be the same for each frame? If the answer to all of these is yes, you probably don’t even have to change the default parameters in the image sequence node.

First let me say I appreciate all the time you put into helping me with this.

Does it start at 0001.exr? Does your blender scene (that’s what I mean by global) also start at frame 1?

I have renamed most of the files now that I have been trying to make it work, and:

  • Global scene (by which I hope Blender tooltips mean the same thing) starts with frame 1220
  • EXR range from number 1220 to 1794
  • PNG range from 1220 to 3921

The PNG image sequence becomes offset by 1219 automatically on import. I only need 575 frames though, so I’ll erase the rest, and rename the remainder to be 1220+.

I noticed that the 1220 in the EXR and PNG do not correspond to the same moment. This shouldn’t have any effect on compositing aside from the image being completely wrong, but I’ll need to fix that before I continue.

EDIT: Another problem - animation rendered black frames, single frame render rendered normally.
The undistort node seemed to cause the problem, but it is necessary to render the proper footage.

Assuming that the image sequence numbers are good and line up with your current scene frame correctly, you should be able to simply use Start Frame = 1220 and Offset =1219.

It’s a bit confusing but here’s how it works: The Start Frame is the frame in your current scene timeline at which Blender will look for the file explicitly labeled 1, or 0001, or 0001, etc. in your image sequence. Not the first file that’s there, but the file recognized as being labelled frame 1.

The offset is the value added or subtracted from that initial 1 we are looking for. On frame 1220 in your scene, we want to use frame_1220.exr and not frame_0001.exr. So we add 1219 using the offset value. Let me know if that works.

Okay, yeah, your explanation resolved the situation; The start frame value was set to 1 - once I set it to correspond with the actual animation, that is 1220, the backdrop in the compositor started to respond appropriately, and it proceeded through the sequence during rendering.

End result was less than inspiring to be very polite, but that’s a problem of tracking.

Thanks again!

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