Technical Slop

Vicious Lie!

This one starts with Tip 7: Filter Skelter: Displace is nice (See: Kai's Power Tips). In particular, with this paragraph:

Note > It is important to understand that the filter works in actual pixel offsets. This means that the effect can vary greatly depending on the size of the initial image! The maps are 200x200x8, as is the sample grid. If the image to be filtered is 800x800 the filter will create offsets the are extending only a quarter as far! You can use the Scale field in the Displace dialog to compensate for this. In most examples, the scale was set to 33 for both x and y. To refresh your mind: 100 equals the `normal' offset of 128 pixels. You can `overdrive' that up to 999, though... In other words, if the effect you see here at 200x200 should be applied to a 800x800 file you would have to have to use 4x the Scale number to achieve that (eg.133/133 instead of 33/33, or more... season to taste)

I was very boggled by that when I first read it. I was still boggled by it after having read it more than a dozen times. So I got busy figuring out what Kai was talking about. Now I'm passing the savings on to you.

Here come the 3 docs that we will be playing with:

The first is our basic Zoom Cube (see The Cubes). Next is Biker Chic 200x200. The little one, the last doc, is Biker Chic 100x100. So far, pretty straight forward, eh? Good.

This is what happens to Biker Chic 200x200 when the Zoom Cube is used with Horizontal: 50% and Vertical: 50%. She is expanded, or zoomed in, but you already knew that.

The question now is: What happens if we do the *exact* same thing to Biker Chic 100x100?

Let's find out.

Doh! That's not the same at all! She got zoomed so much, that she got flipped a little horizontally and vertically. (If you Displace a target pic just right with a Zoom Cube, you can completely flip it horizontally and vertically, which is basically the same as rotating it 90°.)

What's the deal?

Well, Displace doesn't really care about the dimensions of your target except with regards to Stretch to Fit. Other than that, all Displace cares about is percentage and brightness values. This means that 50% = 64px no matter what your doc dimensions are.

Now for the fix. It's not too hard.

Biker Chic 200x200 has a dimension ratio of 200:200. And Biker Chic 100x100 has a dimension ratio of 100:100. Now, 100:200 = 1:2. That means 50%. So... to get the same results with a target of 50% dimensions, use 50% of the percentages. So, 50% of 50% is 25%.

Hmm... kind of a quick explanation. Let's see if it works.

Hopefully Kai's comments on these things now make sense.

(I don't know if you've noticed or not, but knowing your way around fractions and ratios is a good thing. As a matter of fact, so is knowing how to line factor. All sorts of uses.)

So that's what Kai was talking about. Smart fellow. I can't believe it took me so long to figure out. Talk about some massive detective work and some heavy thinking. Gotta love it.

So what's the big vicious lie? To anwer that question, we'll have to take a closer look at the Zoom Cube graphic that I'm so fond of showing.

Take a close look at the examples along the bottom, in particular the first one labeled "50/50". Also know that the examples in the graphic are 100x100. Well, after looking at Biker Chic 200x200 and Biker Chic 100x100, you should see that something is very wrong.

I'm a bad man.

For the examples in my various cube examples, I used Biker Chic 200x200, Displace using the values listed, then sized them down to 100x100.

Yes, I'm a very bad man.