Gimpdome

I have this idea for a rather complex animation hopefully involving a laser cutting letters out of a piece of steel, done entirely in GAP.  I needed a way to make a layer mask of the letters being cut.  This is sort of an initial experimental proof of concept.

I made the "W" using Inkscape's text function and converted it to a path.  I then went in, selected all the nodes and had Inkscape subdivide the path.  The original path had only a few nodes, the new path had 297.

I imported this path into Gimp and then fired up GAP and duplicated the initial .xcf for a total of 297.  Then I just animated a dot moving along the path with Move Path.  For the animation below, I combined the frames to a single image and added one blank frame.

To make an animated layer mask, I will have to take the original frames and then do frames to image a total of 297 times, each of these frames will use "one frame less" from the original 297.  Each image will be flattened and then added as a frame into another animation.  Kinda tedious, but I can't think of another way to do this.  The animation below is just a gif in combine mode with a single dot on each frame.  What I need is one frame with two dots, the next with three, then four, and so on.  The above method is what comes to mind to achieve this.

Yup, looks like exactly the same method.

I am not sure yet what I want to do.  Basically, I would have something like the above, but on a white background, and several layers, each slighly "shorter".

My intention is to create a bump map source, which would then be masked off with the animated layer mask.  The bump map would slowly appear in the sheet of metal as the laser moves.

Yup...I looked over your tutorial.  I didn't think of doing the move path with the different frames, that might work.  Creating the paths in Inkscape will give me a lot more control, tho.