"offset" theory help

Hello FF peeps,

I'm having trouble grasping some (probably basic) aspects of the theory involved with the "offset" node. The issues I'm running into stem from the fact that I tend to work with particle sprite animation, creating 4x4 "filmstrip" assets. Anyway, let me present an example.

Borrowing some of the node work from Sjeiti's "Marble Madness" filter, I can use offset nodes to swirl an image element like so:



That's fine for a singular image element. I feel I have a strong grasp of how offset works for singular image elements like this. The [black..white] spectrum for "Offset H" and "Offset V" represents [-1..1] in UV space of the sampled image (UV space having the interesting property that -1, 0, and 1 are all the same coordinate).

However, let's say that instead of working with a singular image element, I am working with a 4x4 grid of image elements, like this:



Let's also say that I want to apply an offset with unique properties per-tile (such as varying the strength of Sjeiti's swirl algorithm over the 16 frames of my 4x4 grid. Simply tiling the offset inputs does not work:



I think I understand why it doesn't work (the [black..white] spectrum in the tiled offset inputs need to be scaled somehow so that they "fit" into their smaller image area), but I don't exactly understand what I need to do in order to fix it.

I present an offering for any intrepid minds who might have advice to offer on this subject: I created a snippet to transform a curve to a 4x4 grid of block values (useful for such things as ramping a scalar control like "roughness" up and down over the course of 16 frames). See attached snippet.

curve_to_4x4_grid.ffxml

I have a theory of what needs to happen for it to work. If you can attach your work-in-progress filter with the twirls and all, I can try this out. I believe it is a matter of scaling down the offset percentage accordingly, that is, if the original offset percentage is "x", for a 4x4 grid it would be x/4. It may not be that simple, but the answer probably lies somewhere in that direction.

I see what you mean. The basic problem is that you should not change the offset percentage from frame to frame but the Swirl slider setting (and thus the resulting offset images. In other words, the offset % should be 25 throughout but the two images that create the swirl (that are plugged into the offset x and offset y) should be different in each square of the 4x4 grid, going from 0 to 100 in 16 steps. Follow?

That's a little tricky to achieve at first glance. Let me think of that for a moment.

Oops, looks like I did that simplification on the 16-step grid wrong, so it should be your version of it there instead.

Fixed here:

4x4twirl_3.ffxml

Any time. Challenges R Us.

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Crapadilla wrote: I'm thinking that we should build an article on the Offset component explaining in-depth all the different things you can do with it.

In the Wiki? Sounds like a good idea.

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ThreeDee wrote: In the Wiki? Sounds like a good idea.

Exactly!

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Kraellin wrote: wasnt an offset key in the mirroring filters?

Yup. That would be a special case of a non-uniform scale.

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Kraellin wrote: and then there's just good old plain offsetting

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Crapadilla wrote: Transformations - Translation/Offset