Warp Quality


I like using
top quality modes
for both Draft and Final?

You might want to rethink that if you ever get to the stage of working with a large brush on 6 megapixel images :) It is natural to select High Draft Quality but the meaning of draft quality is rather special for warping and not really equivalent to the sort of quality you think about in connection with interpolation of images. You will find that there is almost no perceptible difference if you work in the Medium Draft Quality Mode, while the warp becomes faster and uses less memory. I think, in fact, we set is as the default for this reason.

Any deformation maps we distribute will be created in this mode to keep their size manageable. Additionally, Photoshop deformation maps don't come in any other flavor but Medium.

For the best compromise between quality on the one hand, and speed and responsiveness on the other: "I'd suggest the Medium mode."

Most likely, you will only see differences between High and Medium Draft Quality with long warps of a very regular pattern like a grid. On most images even Low mode won't make much difference. (Our Low mode is superior to the standard warping in many other packages, in fact.) Additionally, you might want to be aware of another feature. Suppose you start in High mode and switch to Medium during the warp. Those strokes originally made in High Quality will retain their quality even if future strokes are made at Medium Quality. In other words, you never degrade anything you did previously. Yet another thing to know about is that the maximum Hardness of the brush is diminished slightly as you decrease the Draft Quality. Since a brush of maximum Hardness is very rarely used, this isn't going to be much of an issue. You are absolutely right to specify the best Final Apply Quality. This makes far more difference to the visual quality of the final image than anything else in warping because this is where the nonuniform displacement of pixels is taken into account. We only added the "Same As Draft" choice for those people too impatient to wait for the Final Apply. I definitely recommend being patient. -Kris



Should draft mode of the warp brush effect change the apply?

Let's try and summarize some of the ideas behind the Draft Mode in warping: One way to think of the Draft Mode is as a kind of resolution setting for the deformation. In High Draft Mode, very fine changes in pixel position can be represented. In Coarse Draft Mode, we can't define the deformation as accurately. The Medium and Low modes lie in between these two extremes. The less precise the Draft Mode, the faster is the brush. Normally, there is very little difference in appearance between High and Medium Draft Modes, so I would recommend using Medium as the default. It is the best compromise between precision and speed. Why then do we have Low and Coarse Draft Modes?

For small images, we need precise pixel positions because the image has very few pixels and each of them has to be moved accurately to get a smooth warp. However, for a 4 or 6 megapixel image this level of precision is a waste of effort. If we want to make a warp of some size relative to the size of the image we move few pixels in a small image but an enormous number in a large image. For example, in a 200 x 200 pixel image a 100 pixel diameter brush will cover roughly one quarter of the image. To cover one quarter of the image in a 2000 x 2000 pixel image we need a brush that is 1000 pixels in diameter. This huge brush would have to define the displacement of 100 times as many pixels as the brush in the small image and would be 100 times slower as a result. Ouch! So, for very large images we can use a Low or Coarse Draft Mode. We aren't as precise but we don't need to be because we have many pixels to play with, not just a few, and we get a much faster brush. In fact, this is the only way to get a brush that is fast enough to be usable on images of several megapixels.

This image is an example of how the Draft Mode affects the Twirl Brush.

Exactly the same effects occur in Push, Expand, Contract and Left or Right Twirls. Noise is special and I'll deal with it later. The example image comprises pairs of strokes, hard on the left, soft on the right, at the labeled Draft Modes done with a 100 pixel diameter brush. As the Draft Mode decreases from High, to Medium, to Low, to Coarse the warp result begins to look a little ragged and wavy, especially in regions with a large deformation. For the size of image shown in the top portion of Twirl.gif you wouldn't want to use the Coarse mode and might not want to user the Low mode either. The bottom portion of the image shows what happens when you use the Low and Coarse mode on an image twice as big as the former, with a brush size that is also twice as big (200 pixels). After the warp the result image was resized to half the original size for comparison with the former image. You will see that the raggedness or waviness is not nearly as objectionable. At the large size the Low Draft Mode looks a lot like the Medium Draft Mode for the smaller image. For the large size the Coarse Draft Mode is very much like the Low Draft Mode used in the smaller image. So, the general conclusion is that you should use Medium Draft Mode as a default and,

if you are dealing with a large image or the brush becomes painfully slow,
set a lower Draft Mode.


Now let's take a look at the Noise brush using a 200 pixel diameter brush
at maximum Hardness and a maximum value for the Noise control.

The appearance obtained with the various Draft Modes is labeled and it varies very widely. This is the result of the special way noise is created. The brush tries to pack higher and higher spatial frequencies into the deformation up to the maximum possible. When you have a High Draft Mode setting, the pixel positions are described in fine detail and high spatial frequencies can be attained. The result is the "jittery" look at top left. With a Coarse Draft Mode the pixel positions are defined approximately and only low spatial frequencies are possible. Consequently, the result at bottom right shows only smooth, slowly varying deformations.

But what is that thing with the question mark you say? It is actually the Noise brush in High Draft Mode (same as top left) except that the size of the brush is 100 pixels and not 200 pixels. A small brush can be subdivided fewer times than a large brush and so cannot support spatial frequencies as high as a large brush. The end result is that the Noise brush is very dependent on settings.

How "jittery" it is depends on the size of the brush as well as on the Draft Mode you use. To make the brush more "jittery" increase it's size and/or set a higher Draft Mode and set the Noise control to maximum. To make the brush less "jittery", do the opposite. Setting the brush Strength control to less than the maximum will reduce the "jittery" effect but not quite the way it changes with decreasing Draft Mode quality. The effect is hard to describe verbally and is simply best seen in an image. All the Noise brush samples were done with the maximum setting of the Noise control because this is where differences are most apparent. At a minimum setting of the Noise control, all the strokes will be much more similar and the "jittery" effect will be absent. It's worth doing a little playing around with the Noise brush on a simple image like a grid to get a sense of the range of behaviors it can give you.

I admit we could have made the Noise brush much simpler at the expense of severely restricting the range of effects. You can do this in practice by always working at the minimum Noise setting. You will always get something like you see in the bottom left image (especially if you avoid the High Draft Mode). This could be useful for taking some simple vector shapes, rasterizing them and giving them an "organic" look (e.g. to make a Halloween pumpkin). However, you would never be able to achieve the impressionistic effect at top right. That needs a high Noise setting. We'd rather err on the side of more power than less power, but it does make life a little more complicated and high Noise settings make the brush very sensitive to all the other controls. -Kris

Question: I was playing with warp some more, trying to find the cause of another problem, and on the same checkerboard background, used both the medium quality, and then the high quality draft mode. At the end of this, I clicked on the checkmark to apply it, with the apply mode being finest. The results of the 2 different modes is quite different.

Expected from the above.

Thanks, that explains the difference I was seeing earlier in the warp vs noise amount.

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