Why does the warp brush have a double outline?

Every Warp Brush mode has a Strength of effect. You can think of it as being equivalent to the Opacity setting in a Paint Brush. The way the Strength of the effect works in conjunction with Hardness is the following. In a high Hardness brush you see an inner circle and an outer circle. Everywhere inside the inner circle the effect is applied at the same Strength setting. Between the inner and outer circles the effect tails away from the full Strength setting to nothing.

Let's see how this applies to the actual modes of the brush. In the diagram all the strokes on the left are at a Hardness of zero and on the right at Hardness of 80.

For a soft Push brush you can see that only the center pixel is moved by the maximum amount. Other pixels move less. For a hard Push brush the whole center of the brush is moved bodily across the image, while the surroundings of the center move progressively less. For a soft Expand or Contract brush, the effect is greatest at the center and dies away to the edge. For a hard Expand or Contract brush all the pixels in the center of the brush receive the same change. You can see this because none of the grid lines curve in the center. Everything is either grown or shrunk uniformly. Outside this center region the effect dies away outwards. For a soft Twirl brush the amount of rotation decreases outwards from the center. For a hard Twirl brush everything in the center is rotated by the same amount. You can still see regular grid squares, which are simply rotated. Outside this uniform center region the effect is patched into the image to prevent tears. A soft Noise brush (at minimum and maximum Noise settings) shows a lot of effect at the center and less and less as you move outwards. A hard Noise brush shows the same amount of effect in the whole center ring of the brush. Between the center and outer rings the effect is controlled such that there is no tear between the noisy center and the unchanged image outside the brush. For all brushes other than the Noise brush, a regular grid occurs in the center of the brush. It may be moved from where it was, or it may be larger or smaller, or rotated, but it is everywhere the same in the center of the brush. Noise, of course, is designed to destroy a regular grid so you don't see a regular grid pattern one in a hard Noise brush. However, the amount of noise or, equivalently, the amount of displacement of the grid, is everywhere the same (on average) in the center of a hard Noise brush. Outside this center it varies.


I'm afraid I have had my nose stuck in this so long that I may be making unjustified assumptions about how easy this is to understand. Let me have another go at explaining what is going on.



TIP - Draft Modes

I opened the checkerboard, created a twirl, using high quality mode. Then I changed the quality mode, and the twirl that was already created changed the way it looked according to the quality I was in.

I figured if the quality of the view changed, when the image had not, and since the choices for final apply were -finest and -same as draft quality, that the 2nd choice would actually show me the way the warp had been created, and the first would change any warp to the highest possible quality before applying it.

Hmm... not sure if I am making myself clear here. I figured the underlying image was warping the same amount, even the redraw was only showing the chosen quality, and that when finest was applied, that no matter what the draft, it would all look as if it had been created in high quality draft.... did that make sense? I guess part of my confusion was looking at how things were labeled, how they changed with the change of quality mode, and then my incorrect guess at the background workings.

I think I'm understanding what you say. The way things work is this:

Suppose you start out at High Draft mode and make a warp.  The warp is rendered at High Draft Mode.

Now you change the Draft Mode to Coarse. The first thing that happens is that the warp you just made is re-rendered in Coarse mode on the screen. However, the program remembers that you made the stroke at a High setting.

Now, still in Coarse mode, you make a second stroke. This stroke too is rendered in Coarse mode.

However, because it was initially rendered in Coarse mode, the second stroke can't be significantly improved by switching back to High at this point.

OK, so we have the first stroke made at High Draft Mode and the second at Coarse Draft Mode, both currently rendered on-screen at Coarse Draft Mode.

When we do the Final Apply the first stroke is smoother and nicer than the second stroke.

This is because at Final Apply time the program recalls that the first stroke was made at High Draft Mode.

At any given time during warping all of the warp has to be displayed at the currently selected Draft Mode (without regard to the Draft Mode at which each part of the warp was created). Only in this way can we get the brush speed-up resulting from using a lower quality Draft Mode.

I've attached an image that illustrates what I explained verbally. -->

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