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Brush dynamics problem - thinner on one side.

Aug 14, 2013, 00:22
Post: #1
Brush dynamics problem - thinner on one side.
Dynamics is the bane of my existence. I thought I finally figured it out today, but no, apparently I still suck. So my problem is that when I stroke a path with the pen tool, the left side of the line is thinner is thinner than the right side. All I want, is a line that starts small (but not at zero) then gradually gets larger, then at the end, gradually gets small again, but does this UNIFORMLY on both sides. I created my own custom dynamic since non of the presets use only size and pressure (which is what gets simulated when you select "Simulate brush dynamics"). I checked the box for size determined by pressure, then went into the size setting to change the curve which determines how it's affected. I set up the curve as it's shown in the picture attached, and it creates a line as in the picture. it looks like on the left, it stays fairly small then jumps up a pixel width all of a sudden. I have no idea how this is happening. the red curve is almost exactly uniform on the top and bottom!


P.s. does anyone have a link to a COMPREHENSIVE guide to dynamics with lots of examples? All I could find was a simple tutorial that doesn't teach me anything helpful


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Aug 14, 2013, 20:09
Post: #2
RE: Brush dynamics problem - thinner on one side.
(Aug 14, 2013 07:06)ofnuts Wrote:  Of course, looking at 1100% you aways find weird thingsSmile

Your curve starts horizontally, which means there are only very small changes at the start. To me, at that scale there is nothing to worry about. What you are seeing is the anti-aliasing in action. If the path isn't centered on the pixels, you can go from two gray pixels (path "between" these two pixels) to one single dark pixel (path close to the center of that pixel).

How is the line at 100% zoom?

It looks pretty much the same. That line is not as tiny as you would think at 100%. I'm doing the image at a fairly small size because it was just for practice. that is the nose. It's pretty obvious even zoomed out that the line is not consistent. I've had a lot of problems with the stroke to path option, maybe it's just a limitation of Gimp? I hope not because it took me weeks to get comfortable using this progam and I don't relish the thought of switching to something else again.

why can't photoshop just be freeeee Angry
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Aug 14, 2013, 21:29
Post: #3
RE: Brush dynamics problem - thinner on one side.
(Aug 14, 2013 20:52)ofnuts Wrote:  Posting the pic at 100% would hep us, posting the XCF would be even better... And I stick to my remark about the horizontal beginning of the "size" curve.

Also if you want accurate control over the thickness, why don't you do a closed path with two curves and use it for a selection that you bucket fill?

That doesn't work at small scale because the auto path to selection tool sucks ass, especially with such small lines, it only selects like 4 pixels.

I don't even know why this picture is so small and pixellated. I chose a 1600x1200 template to draw on...

I don't want to start over on a bigger scale. It should not be this hard to stroke a path evenly. I don't get what you mean when you say "horizontal beginning of the "size" curve". It's starting at like a 1-2 pixel size and then jumps up to 3-4 pixel width.
here it is at 100%

I don't want to post .xcf, as it's a whole image i'm working on and I don't feel comfortable posting unfinished art on the internet like that. The screenshot is with all the layers set to invisible except the line


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Aug 15, 2013, 01:34
Post: #4
RE: Brush dynamics problem - thinner on one side.
Quote:1) uh? don't get fooled by the ants... they only show the pixels that are over 50% selected. But on thin lines you get a lot of partially selected pixels for the anti-aliasing. This is normal, so just bucket fill the selection (see what you select from the path in my XCF, and compare the ants to the black stroke)

2) At 1100% everything is pixellated. The size of the canvas doesn't change anything.

3) To stroke a path evenly use "Dynamics off" or untick dynamics in the Stroke Path (or better, stroke a line). " horizontal beginning of the "size" curve" is this:



4) duplicate the image, crop it to a 100x100 extract, and remove the unnecessary layers/channels/paths.

2) no but I mean, even at 100% I can tell things are pixelated.

3) but it's exactly the same on the upper end of the curve. same horizontal...ness. I would understand if it did the same thing on the other side, but it's only on the one side, wtf.

4) how does that help anything? All those layers are necessary because they are part of the picture I am making. none of them are linked, they wouldn't affect it.
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