Result inexplicably not picking up transparency...

So, I was messing around w/ ThreeDee's cool rotatable sphere snippet, and I ran into this strange problem. I'm setting an alpha ... it's there, you can see it. But in the result, there is no alpha. It puts the standard image behind it.

What's going on here? There is not even an 'image' node on the filter.

Wow, I never noticed it before, but half my filters with transparency do the exact same thing.

So, after a little bit of investigative work, it turns out that you HAVE to have the "image" node connected into some part of the filter for the transparency to work correctly. I can't think of a good reason why it is this way, but it works. Just connect it anywhere, and blend it with 0% or something, and voila --

If you keep in mind that FF is designed around working on a single photoshop layer, then the behaviour is totally logical: if no 'custom' layer is present (as in standalone mode), FF defaults to loading a layer that happens to have a completely opaque alpha - the default lifesaver image!

Any areas of your texture that are transparent will show the source layer underneath, as any filter output is always comped over this source layer. You'd have to go to 'File > New Image...' and create a zero alpha image to have an 'empty' and completely transparent source layer to work with.

Consequently, there's no need to turn all your texture filters into effect filters by adding the Image component as a workaround. One just needs to be aware of the source layer being always present.

I understand now, good to know.

Still, took me 20 minutes of pondering to figure out how that is logical, but I think I get it now: It's a difference between a texture filter and an effect filter; you don't expect to modify the original image with a texture filter, just add to it, thus transparent areas get filled with original content. On the other hand, you do expect to modify the original image with an effect filter; you can distort or even take away from it (make it transparent). Damn, that even sounds complex. How about:

Texture Filter (no Image component) = transparent areas are filled with current image

Effect Filter (Image component) = transparent areas become transparent (except on background layer)

(I give up, I can't make it sound simple no matter how I put it.)

lol, 3D. you're not the first to stumble on this one. wait till you start playing with not only 'set alpha' but 'get alpha' and then start tracing the alpha through a long filter, effect or texture. it can drive you nuts trying to remember why the alpha does or doesnt show up in certain places. and it's doubly hard on folks used to working with alpha channels in graphic editors, where it is more intuitive.

We have an item on our todo list for future versions to make this thing less confusing. Most likely, this behavior will be controlled somwehere in filter options, and the setting will have several options like 'blend', 'don't blend' and 'automatic' - the current behavior will apply when 'automatic' is selected.