Thanks for the history lesson Grandpa Dot-tone. I haven't heard mention of a stretch armstrong in many a year. Ever wonder what the hell those were made out of?
And yes, I have used your workaround with using the 0% and adjusting, maybe "do use" it is the better term as I frequently have no time whatsoever to do the index routine. More often I find myself rasterizing and sepping in PS. Also a time consuming and needless exercise if you have vector to begin with but quicker than the index (or halftone, I've used this too just mostly for single color gradients) method. The key is the overprint and controlling it, we’re on the same page there.
Here's the thing, I want everyone thinking about this topic, (and we all are after Dan's invigorating post) to consider that, what Adobe needs to transmit to a rip in order to have truly interlocked gradients is just barely more than two simple percentages. That's it.
This is from experience only and likely not technically correct, but let's say you have a simple square and are filling it with a left to right, Red - Yellow gradient.
Illy parts out each chunk of the gradient into little fill areas that have two values- one for the Red % and one for the Yellow%. This practice of dividing up the gradient fill area is where the banding apparent in all Adobe gradients comes from, though some of that is endemic to gradients naturally. But it's necessary to allow the program to assign the right %s of each of the gradient colors and create a fade in mathematical terms. "You have to draw a line somewhere" appears to be the basic logic here. The more of these little divisions you have, the smoother, more editable and also more difficult for your machine to process the gradient becomes.
{side note: I know, just have a gut feeling, there is a far better way to do this with all the processing capacity at our fingertips these days. Where it is or why no one has done it is a mystery to me. There just has to be some better solution than divvying up the fill area into strips. Perhaps an interlaced sort of approach. Am I right here or what?}
Again, our oversimplified outlook is that within each chunk you have the %s of each color. Let's pretend there's a slice in the middle with 50% Red, 50% Yellow. Well, the rip might receive this and say no problem, 50/50 it is and out put both at your exact screen settings which, would stack them directly on top one another of course. The core issue appears to be that Adobe's program is not telling the rip, "hold on, one of these colors is 50% positive, normal output and one is the other 50%, the negative space or leftover space around it. Illustrator does not preview it like this, as stacked colors with knockout space at 50%, so why the hell would it output to the printer as such? If Illy could assign an orientation to each color, either positive or negative, that essentially flips it's values orientation in relation to the other before talking to the output device I believe our problems might be solved and we may rejoice in truly interlocked halftone gradients.
The other way I've oversimplified this is that, let's be frank about this, Illustrator could easily be setup to do far more than simply flipping the output value signal for one of the colors in a gradient. There are so many possibilities off the top of my head that I'll let you all fill in your own blanks on this. Just fuel for the fire, but Illy could easily apply the gradient as an interlocking set of values, as in the side note above, generating a solid fill with the two of them combined and output the appropriate data to the rip. It could even rasterize the gradients to do this as it already contains a few PS raster effects. It could *gasp* even preview this on-screen for you.
This rant is based on the fact that this is do-able, easily from my viewpoint, and we have more than enough fire-power on the average graphic design workstation to handle the processing needed to achieve this. I can wait five seconds for gradients that look good. The issue seems to lie clearly in, what has been assumed, is Adobe's outlook on Illustrator that they do not want to invest serious development in the product until they recover their money from purchasing macromedia freehand. Illy is still 32 bit, still drills on single processor core, can't output a GD gradient and yet they find time to make stipple brush tools and whatnot? They seem to have forgotten that this is an illustration program for the
print industry. I hate to bitch about software, I'd rather spend time making tight art with it, but this is a worth complaining about and is a major flaw.
Below is a thread regarding my own problems with this on a job. The job ran acceptably but this issue above was a major pain in the d!ck and the acceptable outcome took way too long to pre-press and is still a bandaid. I used the off-set angles approach for this one and there was just barely enough on-press gain to compensate for all the knockout areas that this generated.
http://www.theshirtboard.com/index.php/topic,555.0.html
