Using Blender 3.02

Hi all, I would like to make a 'slider' to switch between two images a la South Park.

Here is what I understand, and where I get lost. If anyone could help I would appreciate it.

I have a grease pencil layer with 2 separate keyframes; one with an open hand, the other with a closed hand.

Step 1 - go to 'object mode' and add a 'TIME OFFSET" modifier to the grease pencil object.

Step 2 - set the modifier to 'fixed frame'.

**At this point I can switch between the two images by selecting either frame 1, or frame 2 in the modifier panel.

Step 3 - if I hover over the 'fixed frame' and right click, then 'Add Driver'. The mode box turns purple as expected. But what settings do I use for the driver?

Ime Offset modifier with driver

Next, add a bone and parent it to the Grease pencil? How do you configure this so the bone will make the driver switch between the two images(time offset keyframes)?

Thank you for any help.

  • $\begingroup$ Hi, this is actually a bunch a questions so i can only point you in the right direction and you'll have to do some research. 1) The driver should be on the Frame Offset not the Mode 2) Using a bone as a driver is kinda over-complicated, you could create a Custom Properties and copy that as a new driver 3) Do you even need a driver? you could just keyframe the Frame Offset $\endgroup$
    – pevinkinel
    Apr 20 at 10:20

1 Answer 1


First of all, you need to add the driver to the Frame Offset. As a driver, I find the most practical for animation is indeed to add a bone's transform values, especially if say you wanted to add more hand positions. Here are the steps you need to take to add a bone as a driver:

  1. go to the Frame Offset driver settings (right click on the Frame Offset value and select Edit Driver)
  2. make sure your input variable is set to 'Transform Channel' (it should be that by default)
  3. in your input variable settings, set the object to the armature that has your bone
  4. in the bone field, select your bone
  5. in the type field, select the bone attribute you want to drive the toggle
  6. set the space to local space

Now when you move your bone on the transform channel you chose, it will toggle between the different frames. If you feel like you have to move your bone too far or not far enough before the toggle happens, you can always multiply or divide your value in your driver expression to change that. For instance, if instead of having 'var' in your expression you have 'var * 0.5', it will the divide the distance needed to operate the toggle by two.

  • $\begingroup$ Thank you wilks and Lipizzaner, but the frame offset does not allow me to create a driver, rather it has a 'copy as new driver' selection. If I should copy it, where would I paste it? $\endgroup$
    – Hal9000
    Apr 24 at 0:28
  • $\begingroup$ @Hal9000 you won't be able to add a driver if you have keyframes, remove the keyframes and it should work fine $\endgroup$
    – pevinkinel
    May 7 at 14:01
  • $\begingroup$ Thank you wilks. For some reason I just can't get it to work. Would you be willing to share a simple example file or something? $\endgroup$
    – Hal9000
    May 7 at 20:02

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