Here is a link to my favorite online sprite sheet generator: https://ezgif.com/maker.
It can both generate sprite sheet from GIF (https://ezgif.com/gif-to-sprite).
Or from Video via a 2-step workflow, so you could basically export your animation render from your favorite 3D app:
1) first make a animated GIF from video (https://ezgif.com/video-to-gif).
2) then make a sprite sheet from GIF equal to the first option mentioned above. Remember to set Frame rate (FPS, max 25fps so consider that in you 3D app video render export settings to be the same. Usually default settings are higher!).
Support for transparency is also possible, but the video needs to support it as well. Just a few codex do support that. I recommend Apple QuickTime (MOV) and the specific container: MPEG-4 - codex: CineForm (CF) - it's actually the only option that works for me in Windows 10 at the moment. In this case also remember to set Method to Preserve transparency!
As we all know GIF does not support anti-aliasing on the edges of transparency. ezgif.com also has a APNG option, so we could work around it: (https://ezgif.com/video-to-apng). Remember to set Frame rate (FPS, max 20fps and consider that in you 3D app video render export settings to be the same. Usually default settings are higher! Also: In my case the 3D app video render was not generating the correct aspect ratio, but there is a convenient resize option in ezgif.com to be used before save to fix that). Now it gets a bit strange (https://ezgif.com/gif-to-sprite), yes that is right , just open the option for GIF, but instead of a GIF upload the PNG ((APNG) you don't have to rename the extension name, system obviously knows when PNG is a APNG or not. If you supply a correct APNG, there are no error messages despite it being a GIF upload option! You will be able to inspect anti-aliasing in the preview after conversion).